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Ask the Expert, Questions & Answers

Before the advent of the MGS Forum where all matters concerning plants and gardening can be discussed, the MGS ran an 'Ask the Expert' service to reply to the questions we received from members on a range of subjects.
Here is a selection of the questions asked and the answers. The questions relate to:

  • oak apples caused by a wasp larva
  • plants for a windswept coastal garden
  • 'the queen of the night', Selenicereus grandifloras: evolutionary perspective of only blooming once a year
  • dieback after rose pruning
  • when to prune apricot trees
  • identifying Hakea lissosperma
  • identifying valonia oak, Quercus ithaburensis ssp. macrolepis
  • pine tree pest Tomicus destruens
  • why white flowers seem to attract more insects than red ones
  • identifying a Lycium; native or introduced?
  • identifying the palm tree pest Paysandisia archon
  • identifying Trachelium caeruleum
  • identifying the caterpillar of the Cucullia santolinae moth
  • diseases of mulberry trees
  • identifying Cynoglossum magellense, an Italian endemic
  • bathing pools
  • vermiculite and asbestos
  • flowers that turn a different colour as they open, mature and die
  • identifying a Solanum as sisymbriifolium or elaeagnifolium
  • the use of  green manures in citrus cultivation
  • dealing with bush crickets, Peocilimon ornatu
  • release of scent from flowers

Question - "I just found an oak tree with strange round woody things on the twigs. I wonder if these things are its nuts or a disease. What kind of oak is this? The tree was found in Greece, Peloponnese (near Andritsaina)."
Read the answer.

Question - "I would like some suggestion about what I can plant in my Kato Koufunissi (Greek island) garden. It is very windy and very dry and very close to the sea. The only vegetation is Myrtus and thyme. Thank you"
Read the answer.

Question - "Please could you address the issue of the toxicity to bees of the neonicotinoids. What is the latest scientific opinion?"
Read the answer.

Question - A member in the Languedoc asked how to identify the larvae found in his compost. The rose chafer (Cetonia aurata), and the common stag beetle (Lucanus cervus) are both very common in this part of the world. He made the following comments:

"Lucanus cervus and a pile of oak leaves – a recipe for great compost

If like me you have many large deciduous oak trees and don’t want to burn the leaves, then turn them into compost. Various articles say they take a long time to rot down, and the result is a bit acidic. Well, my oak leaf compost is ready to use within 9 to 12 months, and my plants don’t seem to mind, what ever the pH is. The secret of my success is hundreds of larvae of Lucanus cervus, the common stag beetle, who eat their way through all the leaves and leave me with compost like the finest loam. 

My compost heap is enclosed by a 5m x 1m-high roll of split bamboo fencing, anchored by four poles. In early spring I fill two of these with my oak leaves, tamping them down well and sprinkling the top with any organic fertilizer to hand, and then a good soaking of water. Then I cover the top with a plastic sheet, and weigh it down with stones to keep it in place during the rigours of the Mistral. I don’t shred the leaves, but throw in any fresh green material to hand at the time to help activate the decomposition, though this is not essential.
The first year I did this, I noticed that after six months the heap had a number of beetle larvae in the bottom which were eating the decaying leaves and creating a central core of a fine loam. After nearly a year they had consumed half the heap. I riddled the heap, saved the larvae and returned them to the heap, to eat any leaves remaining from last year’s supply and start on the new year’s supply.

After 3 years of repeating the cycle, my compost heaps have hundreds of the larvae, which consume everything, leaving only a thin outside skin of a few un-rotted leaves. In just three months the heaps condense by half, so I top them up with leaves saved in bags. Once or twice a year I take the covers off to give them a good watering, and perhaps a light fork over. They can easily dry out in our Mediterranean climate.

These invaluable workers are the larvae of Lucanus cervus, the stag beetle. The larvae have a cream-coloured soft transparent body with six orange legs, and an orange head with sharp brown pincers, and can be as big as 6/7cms. They go through several developmental stages, taking 4 to 6 years to become pupae. The pupae, which settle at the bottom of the compost heap, resemble walnut shells. These should be saved with the larvae.

The adult stag beetle has a short life of three months or so, and some say it feeds only on nectar and tree sap. In the UK they are now an endangered species, found in only a few areas. If you have deciduous oak trees, build them a nursery, and wait for them to fly past in the early summer with their strange buzzing sound. In France it was an ancient sport of children to tie them to a piece of thread and somehow get them to fly whilst one held the other end, like a kite, hence their French name of cerf-volant."
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Question - The following question was received from a member in France: "'The Queen of the night', Selenicereus grandiflorus, is a cactus flower which only blooms one night a year. My question regarding this cactus is what could be the foundation of this life process (of only blooming ONCE a year during the night) from an evolutionary perspective, and also what could be the advantages and disadvantages of this life process?"
Read the answer.

Question - from a member in California. "I'm mystified why some of my roses respond to any kind of cutting back with immediate die back up the stem. This is true for my white banksia rose, but not for my yellow one. It is true for Mme. Alfred Carriere and Paul's Himalayan Musk but not for Alberic Barbier or countless other climbers and ramblers. The dieback is severe and Mme. Alfred is but a shadow of her former self. Cuts made back to a main stem seem less inclined to cause die back. Do any of our MGS rose experts have some suggestions for how to manage this problem? The white banksia, in particular, has very long, drooping stems that need some kind of discipline from time to time if they are not to drape themselves all over the rest of the garden.

The entire garden is likely the same soil type and the roses that are affected are both in full sun and in part sun locations on both sides of the house. I'd say there's a slight increase in the incidence for roses that get less sun but those roses get more abundant moisture in the form of fog drip; most of the full sun roses are watered rarely during the summer and do not suffer from die-back.

The white banksia that suffers from die-back is growing at least fifty feet up in an 80' deodar cedar. The branches that droop low on the ground, onto the lawn, and into the plantings around the tree are the problematic ones. I've taken to looping them further up into the tree to avoid cutting. Not entirely successful.

I just may give up on roses. I'm not sure they're the right plant for our increasingly hot and dry summers in spite of what often comes to us as blessed summer fog."
Read the answer.

Question - "We have been told by local friends (in France) that the time to prune an old apricot tree is now – i.e. in mid-winter. Other friends have told us that we should do it in the spring. What do you advise? I have been googling away without much success. Our tree is about 150 years old and has occasional bumper crops, if the buds aren't frozen off or blown off in the spring."
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Question - "While driving on a mountain road in the Estérel mountain-range on the French riviera, we discovered a mysterious shrub (1m 70) which was growing in complete isolation, far from any habitation, and was in bloom in the month of March. Can you help us identify it?"
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Question - "We live in Pelion, Greece and have a magnificent oak tree on our land. This year it has produced an abundance of acorns, which we would like to grow and naturalise. However, we cannot identify which type of oak it is. It is evergreen and has woolly acorns.

Please find the attached picture of the acorns - and a leaf. These are pretty large acorns. The tree is about 10 metres tall and there are several smaller specimens nearby. At first I thought it was a burr oak - but it is evergreen. We have a lot of holly oaks but this is totally different."
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Question - We have had for about five years an established garden in maquis terrain on a hillside above the Tet river valley in the Roussillon in France. We are about 200m - 240m above sea-level, in a zone where Pinus pinea grow naturally, also Pinus halepensis. Over the last few months we have noticed that about 10 trees (of both types, some large and mature, some smaller) have rapidly developed brown needles in the canopy towards the end of their branches and/or also needle foliage that wilts at the tips of branches. Four so far have gone on to develop completely brown needles, and our gardener has cut two trees down.

He brought in a local tree surgeon earlier in the week, who pointed out that the affected trees had to a greater or lesser extent, small, hardened deposits on the bark or between cracks in the bark, which were creamy/yellow in colour, and vaguely resembled tiny volcanoes, in that they are often circular (typically about 1 or 2 cm in diameter) and have a small hole in the middle leading into the tree. He said they were due to the activities of a moth which lays its eggs on the tree; these then turn into larvae that bore into the tree, eat its sap (hence the volcanoes of excreted, digested material) and then, once the tree is 'dry' and dead or dying, move on as moths (usually by night) to another tree. He said it had no major predators, that it was now a regional problem for both pine trees (with Aleppo pines being more vulnerable than umbrella pines or maritime pines) and cedars (as yet our few cedar trees seem to be all right) and that there was no simple and effective way of tackling it and that all that could be done was to fell affected trees quickly once they were identified as  being under attack; and that once an infestation was under way in a small area, it would be likely to devastate most or all the pine trees. He also said that the deaths were nothing to do with the colder than usual winter just ended or the well-below average rainfalls in Roussillon during the last 4 or 5 years , or with processionary caterpillars. This situation of impending doom, where we can do nothing but gradually fell our trees, is heart-breaking.  The pines are a central feature of the garden and provide key areas of shade; for example the drive up from the road to the house is lined by Aleppo pines of enormous character.

However we can't find anything on the internet that fits our trees' symptoms and what we have been told, nor can we find the word 'ylessine' or anything resembling it. We are therefore beginning to doubt what we have been told in terms of a diagnosis and lack of any feasible cure.

I attach some photos of affected trees; while they show the 'volcanoes', I'm not sure how much they help. We haven't seen any moths or larvae. Further research suggests we were either misinformed or misunderstood what the tree surgeon was telling us in terms of the pest being a moth, and that what we probably have is an outbreak of 'l'hylésine destructeur' in French or Tomicus destruens in Latin. I'm not sure exactly what this in English, but it's a beetle, related to the common pine beetle (which seems to be the name for a slightly different beetle, Tomicus piniperda). If it is indeed Tomicus destruens, then it's relatively new to our part of the Mediterranean and very serious; much of what we were told is confirmed on the net. There seems to be a connection however with drought, in that the beetle tends to (successfully) attack weakened or stressed trees, particularly Aleppo pines.
Read the answer.

Question - Can you explain why white flowers seem to attract more insects than red ones; in the present case, insects teem in the flowers of the white peony (Paeonia spp) while red peonies, only a few centimetres away, are not visited?
Read the answer.

Question - This enquiry was sent to us by a member living in Cyprus. The plant in question is a 2-3m high shrub, growing on a track between Goudi and Polis, in western Cyprus, altitude <50m. As the photos show, it is well-clothed in mid-green entire leaves and red berries. The latter are sub-spherical, and with a distinctive sort of husk (green). The member adds: "I hope you can name this for me!"
Read the answer.

Question - "This year we noticed a very beautiful moth in our garden in the Languedoc Roussillon part of France and took some pictures of it. I wonder if you know this moth? I understand that it comes originally from South America and that it is harmful to palm trees."
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Question - "A few days ago we spotted the plant in the attached photograph flowering in the wild at Ostia Antica, near Rome. We have no idea what it is, can you help? Hmm, I would have said perhaps Trachymene caerulea except that I don't think the leaves look right. It was growing at sea level in the excavations: in ancient Roman times this was a sea port and is now about one kilometre inland because the Tiber estuary/delta has gradually silted up. I did not see any signs of underground water but perhaps was not observant enough.

I found the plant growing in the ruins of a Roman building, as it were in a "room", of course open to the light. It was in a very sunny position, except that the shadow of the walls may fall upon it for a few hours; it was not close to the walls (but rooms in ancient Roman houses were not very large) and was growing in hard, dry, what seemed slightly sandy earth - probably calcareous since the water here is very hard indeed. I found it on 4 September, just before the first autumn rains. The plant was still making buds, and did not yet have any seed at all as it was just beginning to flower.

Almost nothing else was growing there, it was so parched and sun-baked. So imagine the delight of suddenly coming upon sprays of blueish-purple!"
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Question - "Can anyone identify the caterpillars that for the first time have been ravaging our santolinas this year? (Our garden is in a rather arid part of Provence.) There are small apparently black ones and larger slightly bristly ones of a dull brown with greenish-yellow markings on their backs and crescent shapes of the same colour outlined in black on their sides. I suspect that both are the same species, the ‘black’ ones being at an earlier stage of development, for although they appear uniformly dark to the naked eye, a magnified digital photograph reveals faint yellowish markings on their backs corresponding to the marks on the larger caterpillars.

They appeared in late April and early May following heavier than usual winter and spring rains and they stripped 4-year-old santolinas of all their leaves (S. chamaecyparissus and S. neapolitana ‘Edward Bowles’). We have also found them on a neighbouring lavender plant and on wild rosemary plants. Clearly they have a taste for the aromatic.

We have never seen caterpillars on any of these plants before. We’d love to know of what butterfly or moth they are the larvae."
Read the answer.

Question - "It`s a cry for assistance! Our mulberries, which are very important in our garden have begun to die very quickly this week. There are yellow marks on the leaves on the branches and on the fallen leaves. No insects or caterpillars. Perhaps it`s a virus or the spring rains. What should I do? Please could you inform of any internet sites or experts which could help. I have looked at the internet but the information is a little confusing."
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Question - "Attached is a photo of flower taken in the Sibillini mountains yesterday,  I have searched through my library of wild flowers and indeed the internet to no avail. Is there anyone among the experts who could please identify it for me? "
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Question - "I have long been contemplating some sort of water feature/watery element in my garden. I would like to attract wildlife, to enjoy the sight of an area of water and − why not? − when the weather permits, bathe in my "pool". I have read about "natural swimming pools" in a number of books and garden magazines but most seem to be in northern climes. One local garden designer and nurseryman told me categorically that the natural pool could not be achieved here because of our high summer temperatures. Could you advise, please?"
Read the answer.

Question - "I have recently seen articles which report that certain vermiculites could contain asbestos. Could you comment on the health and safety aspects of using vermiculite?"
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Question - " Why do some plants like Hibiscus mutabilis or Rosa chinensis have flowers that turn a different colour as they open, mature and die?"
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Question - "Can you identify this extraordinary plant (below) I found growing in gravel close to Anduze, in Languedoc, France? The gravel was brought in about 10  years ago and overlies an alluvial soil deposit."
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Question - "I want to ask someone about green manures that might help in citrus cultivation. I live in drought-devastated Cyprus and cannot give the many trees I have as much water as they need. (I know they are not good plants for dry gardening, but my house came with lots of them). So I thought I might at least help them with some organic companion plants. I have constraints of what is appropriate and what is available."
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Question - "Suggestions are urgently needed as to how to combat the voracious bush cricket (Peocilimon ornatus?) that visits us in large numbers in the spring in our small garden in southern Greece. The cricket attacks orange and pomegranate trees, eating leaves, buds and young fruit with its very powerful jaws. A year ago the crickets destroyed a very large cistus. The cricket is easily recognisable with its central black stripe and two parallel yellow stripes along its back. On its sides it has very smart markings of green/black chevrons. At the moment, the only mode of defence is to catch and squash these crickets.  This is not difficult but time-consuming and not very effective. Although no chemical addict, I would reckon that an early spray before fruit has set would be safe toxic-wise − but what spray?"
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Question - "Cestrum nocturnum gives off its scent at night in pronounced waves or pulses. How does the plant do this physiologically? And what are the advantages of a pulsed scent rather than a steady scent?"
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Answer (November 2008) - " All flowers have evolved mechanisms to achieve successful pollination. C. nocturnum produces an intensively fragrant "volatile" scent during the night to attract its pollinator, a moth of the noctuid family (Agrotis spp), see page 40 of TMG number 35. The moth relies on the fragrance to guide it to the flower: it has its own GPS system. Moths may be attracted from a distance of over six metres.

The moth has a long proboscis and the ability to hover while drinking the nectar at the base of the flower. The proboscis is guided by a slit in the anther, leaving behind sticky pollen which is then transferred to the next moth, and so on. Up to nine species of hovering moth have been identified as pollinators.

Flower fragrances probably originated to deter herbivores; however, visiting insects selectively chose those flowers which provided food. Another evolutionary scenario could be that moths would be more likely to find a mate also visiting the same flower. The circadian cycle also attracts species that are frequent during the night, for example the noctuid moth.

Scents are usually produced from the metabolism of the cell membrane, with the corolla, pollen or nectar often being involved. The advantage of a pulsed scent compared to a steady scent is not clear. It may be that it reduces olfactory fatigue in the pollinating insect. A "flashing" scent may be more noticeable than a steady scent. Pulsed scents may travel longer distances, the weaker/stronger smell may be more efficient in attracting moths, or it could be a trigger controlled by exterior factors such as temperature. The trait to respond to a scent is rapidly learnt since there is an immediate reward. The pulsing may also be related to the concentration of the chemicals involved. Thus a number of reactions may be involved in the production of the scent and the scent release is stopped until the necessary precursor chemicals are generated.  At some critical concentration the scent is then released again.

Odours are especially prominent in "primitive" plants. There are four categories of odour described as heavy, aromatic, lemon and foxy. The fragrance of C. nocturnum has been described as a mix of musk and heliotrope.

Some other night-flowering plants include Brugmansia candida, Ipomoea alba, Oenothera spp and Petunia spp."

(March 2010) - "Following up on the response already given, I have been looking through the research that has been carried out on Cestrum nocturnum. There is certainly mention of the release of the scent, but I have not found specific research on fragrance being released in pulses. 

The first interesting point is that the scent release is an endogenously (internally) controlled circadian rhythm, i.e. it is found in a cyclic (24h circadian) manner, both in constant darkness and constant light at constant temperature. As scent is usually released in the evening, but the corolla behaves endogenously, there must be an additional ' zeitgeber' (from the German for time-giver, synchronizer) which synchronizes the flower's endogenous (internal) time-keeping system (clock) to the earth's 24-hour light/dark cycle. This might be in another part of the plant, for example the leaves, as the strongest 'zeitgeber' in plants is light although it can also be temperature. Although in nature in constant conditions this rhythm is a period of roughly 24 hours, it is affected by temperature, with the cycle lengthened in colder temperatures and reduced at higher temperatures (Overland, 1960). As mentioned in the previous answer, there may be a number of reactions which would lead to the release of scent, therefore if one or more of these reactions were temperature-dependent the cycle would be extended. 

Research has also been carried out to examine the constituent components of the scent (Al-Reza et al., 2009). The extract was found to contain alkaloids, flavonol glycosides, steroidal saponins, fatty acids, essential oils phenols, and others (Bouchbaver et al., 1995). The chemical components of the scent are volatile compounds which facilitate their release into the atmosphere. As mentioned in the previous answer, scents are usually produced by metabolism of compounds within the cells and the corolla is often involved. The corolla was shown to control this mechanism as the cycle exists independently in excised corolla tips (Overland, 1960).

In snapdragon flowers, the same endogenous activity was shown by examining the release of methyl benzoate, one of the most abundant scent compounds of bee-pollinated snapdragon flowers (Kolosova et al., 2001). This research showed that the total amount of benzoic acid available in the cells was a determining factor in the regulation of the rhythmic emission of scent. This could be evidence that scent is only released once a sufficient supply of precursor chemicals is built up, leading to a pulsed scent. 

A simpler explanation for the observed release of scent could be atmospheric conditions, i.e. temperature fluctuation, humidity or simply very gentle breezes that give the impression of a pulsed release of scent, or additional release of the volatile compounds from the cell surfaces. 

I have discussed this with an evolutionary biologist, Dr Elisabet Sahtouris, and she offered an additional theory that it could also be an economic use of the volatile compounds over a longer period."

Answer (November 2008) - "The best chemicals to use are the synthetic pyrethroids − not pyrethrum. They are extremely active at very low dosages and very effective on most insects but they are broad-spectrum, killing both the good and the bad. There are several products to choose from. The common names of some of the active ingredients are: permethrin, deltamethrin and cypermethrin.

You should be able to find these in a garden store or at your local agricultural co-operative. They are sold under several trademarks. The key is to ask or look for the common name on the label.

These products are effective as contact sprays (direct your spray at the adult) or by ingestion,  assuming they eat a lethal dose on the plant they will die. These products are quite persistent, especially permethrin.

There are baits available, for example "Advion" from Dupont. You might ask if it is available locally. I have never made a cricket bait but it would be worth a go. It is directed at the pests and is therefore more specific. Try mixing oatmeal, rice, or cornflakes, whatever you think may be attractive to the adult, with a solution of the insecticide you use, i.e. deltamethrin. Try 1 part in 1000 parts and mix in with the bait. Wear gloves."

Answer (December 2008) - "Our first expert was dubious of the value of cover crops, saying that citrus trees are natives of South East Asia where rain is usually plentiful and that irrigation is indispensable. Any benefits accruing from companion plants may be outweighed by the competition for water with the citrus trees.

Several companion plants were suggested including any local vetch or medic, clover (Trifolium spp.) or even Phaseolus beans. Broad beans (Vicia faba) and Sinapis arvensis had been successfully tried, mainly because seed was available. These plants should be heavily seeded with autumn rains and scratched into the soil surface. The additional nitrogen from the legumes was considered to be beneficial. The companion crop should die down with the onset of summer heat and form a mulch. However, if this does not happen the companion plant can be "burnt-off" with glyphosate. This will eliminate competition for any available water.

The decorative perennial Aptenia was considered an excellent cover crop; however, whether it would do in this situation is open to debate.

One expert recommended that on no account should the mulch or cover crop be turned into the soil. Cultivation led to loss of organic matter through photodecomposition, destroyed soil structure leading to run-off and soil erosion, as well as to the loss of earthworms and other microorganisms.

Yet another expert advised "any kind of mulch" to improve water retention. Citrus trees are heavy feeders and it would be good to have the mulch well rotted so that the decomposition process does not rob nitrogen from the soil. The mulch is recommended to be at least 12" (30 cm) from the trunk of the tree. Cotton waste, waste grapes and stalks from local wineries, shredded and composted vegetable waste from municipal recycling plants could all be used. Any sort of "hard" mulch is recommended, including gravel and local stones.

Finally Jennifer Gay's gardening column in the Athens News was recommended for local practical experience:
"Concerning your recent article on cover crops, we are considering implementing this on some unfinished land. The earth there is like rock, so we are considering bell beans or mustard radishes, with strong taproots to try, and I assume these come in seed form, but can you recommend anywhere in Athens to get these seeds?
Greek agronomists tell me that farmers here traditionally used the method, often doubling green manure up as a fodder crop, eaten off by animals. As winter ended, it was ploughed into the ground. It is quite possible that, with the advent of inorganic fertilisers, people have forgotten the importance of turning in crops at the end of the season. It should be possible to buy cover crop seed in most garden stores. Two such crops commonly still in use are bell bean (Vicia faba), or alfalfa/lucerne (Medicago sativa). I don't know the Greek for the oilseed radish I mentioned, but the Latin name is often shown on the packet and is Raphanus sativus var oleiferus. It is a variant of the Greek native Raphanus sativus."

Answer (December 2008) - "It is impossible to identify accurately plants a) from a photograph and b) without floral parts. Identification from vegetation is at best, a best guess.

However there is a great possibility that this plant is Solanum sisymbrifolium, a member of the Solanaceae, naturalised from tropical America.

This plant is definitely not Solanum elaeagnifolium, silver-leaved nightshade, which is a "dreadful spreading invasive" in the Mediterranean."

Answer (January 2009) - "Flower colour depends on the presence of pigments in the flower (or leaves, stems and fruit), upon the pH (the acidity or alkalinity), the genetic make-up and other conditions of the sap in the plant cell. Several pigments are concerned. The most common are the yellow and orange colours contained within the cell plastid (a cellule containing the chloroplasts), the red, purple, blue and orange anthocyanins and the yellow to ivory anthoxanthins. Flowers contain some pigments but not others.

Background effects are shown when two different-coloured pigments are present. 

Colour variation and change may be brought about by dilution or intensification of the pigment present within the cell and all show a marked sensitivity to the pH of the cell sap.  For example, under acid conditions red colours are more pronounced but under alkaline conditions blues/violets are stronger. This leads to different colours in the same flower. Pigments are also water-soluble, giving rise to "local" variation.

The colour change in Lathyrus hirsutus, hairy vetch, is well studied. The mature standard petal is pale blueish red and fades through blue to greenish blue; the wing petals are pale blue and fade to greenish blue. The pH of the sap in the wings is higher than that in the standard petal and this may account for the bluer appearance in the wing petal.

Flower pigments play an important role in the attraction of pollinators.

Another theory highlights the importance of pollination and colour change. In a study with yellow Lantana flowers the presence of one grain of pollen triggered the synthesis of anthocyanins which masked the existing carotenoid colours. Since thrips are attracted only to yellow flowers, the change in colour may be attributed to conserving the energy of the pollinator insect."

Answer (March 2009) - "Vermiculite is a naturally occurring mineral generally derived from mica. On heating, mica granules expand greatly to give a lightweight highly water-absorbent material that is used in horticulture and in numerous industrial applications including in plaster, mortar, in concrete and as insulation in walls, floors and ceilings. It has been demonstrated to be safe to use, and no serious health risks have been found to result from exposure to vermiculite.

During the 1960s one particular mine in the USA was found to be producing vermiculite contaminated with asbestiform material. The contamination was due to the fact that the vermiculite sat directly on top of an asbestos deposit.

All naturally occurring materials have characteristics which reflect the particular deposit where the stuff is being mined, thus asbestos contamination may exist for a wide range of materials including sand, clay and gypsum.

There are numerous sources of commercial vermiculite ores in the world which are currently in use by the major producers and which do not pose a risk to the user. In fact it is estimated that over 500,000 tonnes of vermiculite are safely mined and sold around the world per annum.

It is important, however, to note that the possibility of fibrous asbestos contamination exists for a wide range of naturally occurring materials and it is thus inappropriate to state that any such material is asbestos-free.

The above represents a summary of the information available on vermiculite. In our opinion members of the MGS should be aware that a risk, however small, may exist with all naturally occurring products; it is up to each member to make his own assessment of risk based on his exposure to them."

Answer (March 2009) - "Our experience is that it is perfectly possible to have a swimming pond in quite an extreme climate: we are zone 10 in gardening terms, which means that we rarely get frost and have highs of 40°C occasionally in the summer months but more regularly up to 30°C air temperature. The aim of the pool constructors is to match the plant community used to clean the pond water to the make-up of the water itself, thus copying nature and providing an experience similar to that of bathing in a river or lake. Size and shape is not important and you can have a dizzying variety of shapes, with large rocks, cascades, bridges etc. Have a look at the gallery section on the web site below for some ideas.

We have had our pond since June 2005 and it is just great, every year bringing more maturity in to the plantings and the surroundings. We have tried to keep these in tune with the landscape as much as possible, using large drought tolerant grasses and native plants, gravel, large flat stones and some small paved areas for contrast. We have many visitors and even those who are a bit sceptical about swimming in a pond have always jumped in and thoroughly enjoyed being eyeball to eyeball with little frogs on the lily pad leaves, seeing the spectacular red and blue dragonflies at close quarters and watching the swallows dunking themselves in the pond. It is good not to have to worry about chlorine, salt or any other water treatments, we can flop in and out of the pond as many times a day as we like and our skin, sinuses (and bathing suits) are soft and sweet-smelling.

Rosie Peddle wrote an article in the MGS journal, TMG 44, April 2006, entitled "A pond for swimming in".

There is a lovely blog by another MGS member in Umbria. (Click on the pond link in the list of topics.)

The International Federation of Natural Bathing also has a gallery of photos of ponds."

Answer (June 2009) - "The plant has been identified as Cynoglossum magellense, a Boraginaceae and an Italian endemic.

The photo was taken by an MGS member in the National Park of Mount Sibillini in Italy. The park was established in 1993 and covers some 70,000 hectares and reaches an altitude of 2,500m."

Answer (July 2009) - "It is very difficult to give a precise answer from a written description however there are two diseases recorded on “mulberry”. Gibberella moricola or canker and die-back of mulberry has been recorded in France and Italy. The most conspicuous features are large cankers on the stems beyond which the foliage turns yellow and wilts leading to die back. This genus has been reported to cause rapid wilting of the leaves followed by chlorosis and necrosis. A cross-section of the infected leaf/branch should show vascular discoloration.

Another authority confirmed that G. baccata is the commonest cause of shoot and twig dieback of Morus.

There is little published data however one reference did recommend that hygiene would help (which does not help very much) or the use of a modern systemic fungicide such as benomyl or thiabendazole.

The other recorded disease is Rosellinia aquila which has been reported to invade the roots of mulberry trees. When a large part of the roots are infected there is a progressive yellowing of the leaves and die-back!

I think I would be tempted to cut out the disease branches well below the infected area. Burn the cuttings and collect and leaves and burn. A drench of one of the systemics listed above may help but I realise this may be difficult on mature mulberry trees."

Answer (August 2009) - "The plants on which caterpillars feed are very indicative of their species. A search for santolina indicates (as far as I can discover – but my information could be very far from complete) two species of moth whose larvae feed on this plant: Eupithecia santolinata, a rare species found in Provence, and Cucullia santolinae, which seems to be more common around the Mediterranean. I tend to plump for this species.

The members raising the question also agree that their caterpillar resembles the latter species."

Answer (September 2009) - "This is Trachelium caeruleum, a not uncommon plant in the Mediterranean. It often likes damp walls in shade, though."

Answer (December 2009) - "This is a photograph of Paysandisia archon, a moth belonging to the Castniidae family with a palm-boring caterpillar. It is a native pest of Argentina and Uruguay and was first recorded in France in 1999, in Spain in 2001 and in Mallorca in 2003. It is now recorded throughout the Mediterranean Basin including in France, Italy, Spain and the Balearic islands. Its larvae attack many palms, but prefer - in order - Chamaerops humilis, Phoenix canariensis, Trachycarpus fortunei and Washingtonia spp.

At home the Paysandisia archon larva infests palm trees but it is kept in check by natural predators and parasites. It appears to have been brought to Europe accidentally on imported palms which are now being planted by many municipalities throughout the Mediterranean Basin to replace the existing plane trees, many of which are old and diseased.

The beautiful moth is large, some 90-110mm across, with dark green front wings with brown streaking, and bright red back wings with bold black and white markings. The adults fly during the day from May to September. Eggs are laid in the palm crowns where the grubs hatch. The caterpillar first eats tender leaves at the heart and then bores into the trunk during a period of one to two years.The first sign of attack is a very regular series of holes in the emerging fronds. Later, there will be piles of sawdust mixed with excrement at the base of the fronds and finally, after pruning, holes and even cocoons will be seen in the base. The grub will over-winter and will stay in the larval stage for up to 18 months. Without control the plant will eventually wilt and die.

Detection and control are difficult as larvae cannot be seen or reached easily within the crown. Periodic inspections will reveal any damage in the emerging young fronds. Chamaerops humilis is especially vulnerable as its heart is so small. Since this moth is not a pest in its native country no control method has yet been developed. It is believed that the moth could spread to a much larger region in the future if measures are not taken; however, natural predators may also be introduced with the imported palms.

A good soaking of the heart with an insecticide containing chlorpyriphos and dimethoate should be effective; this is not a general recommendation, however, and appropriate authorities should be contacted before any attempt is made to spray these pests.

In Nîmes, specimen palms are covered with large plastic netting to prevent egg-laying but this does take away some of the beauty of the palm tree.

Rhynchophorus ferrugineus is another pest of imported palm trees. This is a member of the coleoptera originating in Asia and Malaysia which arrived in Spain in 1995 and was first detected in Mallorca in 2006. It attacks a great variety of palms, with a preference for Phoenix canariensis, Phoenix dactylifera, and Washingtonia spp.

The adult is 2-5cm long and 1 cm wide, coloured red, with black spots on the body, corrugated wing sheaths, and a long beak.

The first parts of the palm to be attacked are the most tender leaves at the heart and then the trunk. Usually the first sign of damage is the collapse of the central fronds, by which time the palm is moribund.

In view of the dangers posed by this pest and the absence to date of effective treatments, experiments are being carried out in many different areas of the Mediterranean, ranging from spraying regularly through the summer, through avoiding pruning except in the winter, to zapping the crown of an infected palm with a batch of microwave "ovens" mounted on extended forklifts.

Please see page 15 of TMG 56 for additional information"

Answer (January 2010) - "I think the plant is a species of Lycium and some of our specimens, L. barbarum (Duke of Argyll's tea-tree), match the photos. L. barbarum is not recorded for Greece in the Flora Europaea, but it does say that this Chinese plant has been widely planted as hedging in the Mediterranean. It has bright red fruits that look like little tomatoes, though with this family they could be poisonous!

However, another expert considers the plant to be Lycium schweinfurthii, which is apparently common in Cyprus and can have red or dark spherical berries. Lycium is a member of the Solanaceae family. L. chinense (Chinese boxthorn) is widely distributed in eastern China and L. barbarum is mainly localised in China. Fresh leaves and ripe berries are common in Chinese cooking.

The seeds of L. barbarum are commercially available from a French seeds company, Baumaux, and are described under the name "Goji" in its 2010 spring seed catalogue, page 581. Baumaux claims that this plant contains 400 times more vitamin C than the orange, and 13% more protein than wheat."

Answer (June 2010) - "Over the years, research has been carried out investigating flower colour and attractiveness to insect pollinators. Within a single plant species where flower colour differences exist research has been concentrated on the flowers on a plant that change colour with age. Investigations have shown that the effect of floral colour change has a direct effect on attractiveness to insects.

Research carried out by Oberrath studied the effect of floral colour change on the attraction of insect pollinators to the herb lungwort, Pulmonaria collina. Lungwort flowers change colour with age from red to blue. Young red flowers had a significantly greater pollen and nectar reward and were significantly more often unpollinated than old blue ones. Red and blue flowers both influenced the long-distance attractiveness of plants but short-distance attractiveness, defined as the number of flowers visited successively on an individual plant, was influenced mainly by the number of young red flowers. The co-occurrence of the change in reproductive ability, in amount of reward, and in flower colour enabled lungwort plants to direct pollinators to reproductive, highly rewarding red flowers. The data suggest that by maintaining changed flowers lungwort plants can increase their long-distance attraction and simultaneously enhance the probability of visits to pre-changed flowers. Oberrath proposed floral colour change as a mechanism that can increase the efficiency of pollen transfer to enhance plant fitness.

Research was also carried out by Ida and Kudo (2008) on bees visiting Weigela middendorffiana whose flowers change colour from yellow to red. Red-phase flowers no longer have a sexual function and nectar, and bumblebees selectively visit yellow-phase flowers. These authors found that retaining red-phase flowers (unlike in the lungwort research above) had no effect on attractiveness to bee visitors.

Specific research carried out on the peony in 2006 (MacKenzie et al.) concentrated on scent rather than colour. This research centred on the wasp Polistes dominulus and its attraction to budding peonies. It concluded that the wasps showed significant orientation response to peony bud odour, but no response to peony foliage odour when compared to the control.

Pheromone traps of various colours were investigated by Clare et al. (2000) to investigate capture of non target bee species. It found that honey bees were most attracted to white traps followed by blue, while bumble bees were most attracted to blue traps. Native bees (New Zealand) were seen most often in white traps followed by in yellow and green ones. The study found that the target pest insects were not influenced by colour and thus recommended use of green or red traps to avoid capture of bee species.

Other potential reasons for colour preference could involve colour contrasts and the time of day when insects visit. White gives a much stronger contrast to the green foliage of peony than would exist in the red variety. Blue colours appear stronger later in the afternoon and may appeal to certain insect species. Some insects may also have a stronger attraction to UV radiation or a combination of colour and, over larger distances, odour. It would seem reasonable to conclude that each insect species has different colour and odour preferences. Perhaps while the white peony was visited most by certain insects, the red peony may be visited by another species at a different time of day."

Answer: (September 2010) - "I've never come across the term 'hylésine du pin' but we must assume that it is the local (French) name for Tomicus destruens, (we have T. piniperda in the UK) and I agree that the damage looks typical of a Tomicus attack. The current distribution of T. destruens is in southern Europe. Although attacks by both of these beetles can be serious and result in tree death, there is usually some underlying problem with the trees that has predisposed them to attack in the first instance. I wonder if the trees were suffering from drought or some other stress."

Website Editor’s note: The following links will take you to the website of the French Department of Forest Health, where you will find details in French on the distribution of the destructive "hylésine" and how to fight it. 
Département de la santé des forêts - Information technique N° 58 - Echelon technique Sud - Est - Juin 2008 

Signe Groos has written of the problems caused to pine trees in the Balearics by Tomicus. (See "Pine Tree Pests" at the bottom of the page.)

Answer: (November 2010) - "This looks like the Vallonea or Valonia oak, Quercus ithaburensis ssp. macrolepis. Its former name was Q. aegilops. You may also find it listed as Q. macrolepis but it is now usually considered to be a subspecies of Q. ithaburensis."

Further information can be found here.

Answer: (May 2011) - "This mysterious shrub in the Estérel mountains is Hakea lissosperma, a Proteaceae (often wrongly labelled as Hakea sericea in gardens, which it is not). It is native to Queensland and New South Wales in Australia. It is well-naturalised and even got into Flora Europaea."

Answer: (August 2012)
"Stone fruits, including cherries, apricots and peaches, suffer from a condition known as gummosis.

Photos by André Pélissier

This is a physiological disorder and is the natural response of the tree to injury. Injury may be caused by mechanical damage including pruning cuts, insect damage, bacterial canker and diseases. The tree oozes a thick, gooey, jelly-like material, which is not at all attractive. There appears to be no known cure for gummosis although you will find some suggestions to use anti-bacterial agents on the internet.

Apricots respond to damage, especially following pruning cuts. Gummosis appears to be aggravated by wet weather; thus the best/safest time to prune apricots is in dry weather. I have seen a small orchard wiped out over 4 or 5 years by gummosis. I suggest you start pruning in, say, May.

Apricots fruit on two-year-old wood, i.e. new wood which grows this year; this wood will bear fruit in 2013. Therefore you need to encourage strong new growth by pruning hard in May. Cut out old wood and reduce all branches to a (natural) leader. Then start pruning to produce young new shoots this year, 2012, which will flower and fruit next year. New laterals will still grow this year.

Easy to say but not always very practical if you have to find your way around. Anyhow have a go. Good luck."

Reply: "We have definitely been doing it all wrong for years, we don't deserve to have had any apricots at all!  We will wait until spring and give it a good haircut then."

Answers: (November 2012)

1. "Die back is quite a problem and seems particularly strange that some roses are suffering while others not in the same garden especially for varieties like the white banksia and PHMusk which I would regard as faintly full proof especially in California. I think I need to ask some questions, are the roses that are suffering in different locations to the ones that aren't or in different soil types? What about amount of sun, shade from trees, from buildings. Less/ more water?

I agree unless the banksias are able to grow into large trees or cover large areas they will certainly need a lot of keeping under control. It sounds a bit of a mystery, the banksias certainly like lots of sun, the more the better. 80 ft up into a tree sounds magnificent
I shouldn't give upon roses that are wonderful plants just a matter of finding the right varieties and sounds as though most are doing well."

2. Here is another opinion: "Die-back is not a specific disease. It can be caused by frost damage, canker at the base of the stem, water logging, mildew or black spot. Yellow and orange varieties are more susceptible. A common cause is a deficiency of potash, calcium phosphates and boron. Feeding is essential in spring where die-back is a problem. Do not feed in the autumn as this leads to "soft" growth. Cut out the affected shoot at a bud below the dead area."

"Have you tried disinfecting your secateurs?" (Ed.)

Answer: (November 2012)

These replies were received from two research Professors:

"Well, this question is one to which I have no firm answers. It is always interesting to try to find explanations for characters of plants or animals, and often this remains speculation. Flowers that open only for a short period are common among flowering plants; others that stay open longer may partition their effort such that the female part (stigma) is only receptive for a short period, and this period is separated from the time that pollen is shed so that self-pollination is prohibited. Other plant species encourage self-pollination, which can be of great benefit if animal pollinators are rare. Night-flowering plants are pollinated by animals that fly at night, generally moths or bats; I do not know what pollinates this cactus (I work a bit on its genetics, not its functional biology!). I was unaware that not only does this cactus have flowers that bloom only once, but that the entire plant has flowers only once a year. I cannot think of a biological explanation for why that life history should have evolved."

And the second: "These kind of nocturnal plants produce flowers during long season. I refer to Selenicereus sp and Hylocereus sp both have the name of "Queen of the night". They do produce flowers which bloom only for one night. However they keep on producing flowers as long as the external conditions induce production of flower buds. According to my own research both long days and cytokinins are essential for flower bud production. As why their evolution produced this kind of a plant? Not always we can offer logical explanations."

Further on-line research revealed the following: The family Cactaceae consists of around 1500 species being mostly leafless trees or shrubs of succulent appearance and often having attractive scent and flowers.
S. grandiflorus is a vine-like spiny cactus native to the Caribbean and Central America. It blooms one night annually. Moths pollinate their delicate flowers. Buds reach grapefruit size, then open in one hour to 1-foot diameter white flowers. Water loss from large flowers is extreme and so cacti generally keep theirs open for very limited periods.

S.grandiflorus is pollinated by night-flying moths. The flowers open in the evening after dark and close by morning before sunrise. Nocturnal blooms occur where night blooming gives the plant a "competitive edge" over day bloomers. For example, in hot climates, sweet nectar and delicate flowers do not dry out as quickly at night. And the pollen is white. Meristematic cells (dividing cells) are more tolerant of extreme temperatures compared to chlorenchyma (cells containing chloroplasts) and may reflect an additional strategy for cacti to survive extreme temperatures.

Flowering at night is just one of many adaptations cacti have evolved to conserve moisture in hot dry climates. Moths pollinate the flowers, but despite being nocturnal they still use light to navigate and seek out flowers. (Flowering when there is a moon maximises the likelyhood of a moth finding and pollinating flowers). Plants like  Selenicereus flower at night, when temperatures are low and the creatures that pollinate them are about. A white flower opening at night is highly visible, so nocturnal flowering makes sense in evolutionary terms.

"…. I had a night blooming Cereus that bloomed sequentially for several nights and was always very noticeable for its very strong sweet aroma. I understand that these cactuses have evolved to match their pollinators which are moths of the night, hence the white flower and strong fragrance". 

What conclusions can be drawn: The advantage is that night flowering conserves moisture in hot dry climates and white flowers are very visible to its noctunal flying pollinators. Disadvantages could be that moth pollinators may not be available due to adverse weather and /or their own pest problem.

Dr Alan Jones says white flowers suggest this species is pollinated by night-flying moths, which are the most visible flowers at night, particularly during full-moon nights. This species produces large, highly fragranced (and, therefore, highly attractive) flowers. By minimising the time spent investing in this organ, and being synchronous with other members of the species, this plant minimises the total 'cost' of reproduction and maximises its chance of reproductive success. This is essentially the basis of natural selection. Selenicereus grandiflorus maximises pollination potential by putting all its 'eggs in one basket' in one night, monopolising pollinator activity for several hours - by sheer force of numbers. This strategy will go wrong if the timing coincides with adverse weather conditions."

Thanks to

Answer: (January 2013)

Larvae of these Coleoptera beetles are classically C-shaped with a well-developed head and swollen posterior.
Larvae of the stag beetle are 8cm long and 2cm thick with an orange-coloured head with sharp brown slightly curved pincers, whereas the rose chafer, Cetonia aurata, is only 3.5cm long, often tightly curled and covered with fine pink hair.

The larvae of both species are very good at aiding decomposition and should be encouraged in compost heaps. Both will feed on plant roots. Any compost should therefore be free of larvae before it is used, especially when used in containers or pots.

For detailed information on identification of larvae, click here.

Answer: (February 2013)

Professor Dave Goulson says "The European Food Standards Agency recently reviewed the safety of neonicotinoid insecticides, and concluded that the three most widely used compounds, imidacloprid, clothianidin and thiamethoxam, pose an unacceptable risk when used on any crop visited by bees (e.g. oilseed rape, sunflower, maize). This decision is based on a number of recent scientific studies which demonstrate that the concentrations of neonicotinoids found in the pollen and nectar of treated crops are sufficient to have a range of impacts upon bees, including impaired ability to navigate and collect food, and reduced colony growth and reproduction in bumblebees. Concern has been heightened by recent evidence which suggests that neonicotinoids accumulate in soils and so are found in untreated follow-on crops, and that clouds of neonicotinoid dust are created during sowing of treated seeds which can kill bees and contaminate hedgerows. My personal opinion is that the EFSA stance is justified and sensible. However, it is important to realize that bees do also face many other threats, including a shortage of flowers in modern intensively farmed landscapes, and various parasites and diseases. Placing a moratorium on neonicotinoid use will not at one stroke solve all our bees’ problems."

Editor's note: "We remind you that mediterranean plants thrive in their natural habitat without any chemical assistance. The MGS promotes a model of sustainable gardening in which phytosanitary products are not used, as demonstrated in our pioneering garden of Sparoza where plants are grown successfully without any pesticides or herbicides at all."

Answer: (June 2013)

I think the best piece of advice I can give you without knowing the location is to look at your neighbours` gardens or better still the local flora and see what is growing. From my experience there is a range of plants that grow by the sea, for example: Tamarix ramosissima, Santolina, Senecio cineraria and Sedum acre. Russelia, Sansevieria, annual Coleus and  Ficus deltoidea all grow by the sea but your conditions might be too dry for them.
The dwarf palm, Chamaerops humilis, grows on the cliffs in Sicily where it is  very exposed. Other woody shrubs you might try are Arbutus unedo,  Elaeagnus x macrophylla (formerly E. x ebbingei)and Rhamnus alaternus (buckthorn).

Bulbs do well, for example Agapanthus, Asphodelus, Muscari, Sternbergia, Scilla and Narcissus 'Thalia'.

Aloes, Acacia longifolia, Artemisia spp., Calendula officinalis, Ceanothus gloriosus, Centranthus ruber,  Dianthus spp., Echinops (the globe thistle), theechiums, Eryngium (the sea holly), Escallonia, the Californian poppy(Eschscholzia californica) grown from seed, Gaura lindheimeri, Griselinia littoralis, helichrysums, rosemary, sedums, Spartium junceum and the grasses Festuca glauca and Stipa are all reported in the literature to grow well. in dry conditions near the sea.

Several plants from New Zealand are recommended includingphormiums, Pittosporum and Corokia.

Carpobrotus makes an excellent ground cover but it is invasive, as is the pampas grass Cortaderia. You could also try Juniperus oxycedrus, Pistacia lentiscus, wild asparagus, Capparis spinosa (the caper), Salvia fruticosa (formerly S. triloba), Teucrium spp. etc.

Do you have Olivier Filippi`s book The Dry Gardening Handbook?  He has many pictures taken close to the sea which will give you more ideas.

Answer: (September 2013)

The woody round things look like galls (oak apples) caused by a wasp larva. There are several oak species found in Greece, the leaves look like downy oak, Quercus pubescens but it could easily be another oak species.
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