August 31, 2012 7:52 pm

Tree trouble

Many favourites are threatened by human carelessness, diseases and mysterious natural causes
A wildfire on the Greek island of Chios in August©Alexandros Vlachos/EPA

A wildfire on the Greek island of Chios in August

Be thankful you are not a tree. Every summer, scare stories circulate but this year the evidence is sickly, sterile or smoking. Palm trees are under attack. Apples have lost most of their usual crop. My namesakes, the Robinias, are mortally and mysteriously ill. Larches are being felled on official orders because they encourage a deadly disease. Horse chestnuts are still infected with a recently arrived insect, while some have a deadly canker too. Oaks are under threat from a SOD. This SOD is a Sudden Oak Death that nobody yet knows how to control. I have recently seen maples under sentence of death in New England but I have not seen two fearful August tragedies. One is the fire in the nature reserve on the Canary Islands that has ravaged the reservations of indigenous plants. The other is the worst news of all, the fire in the woodlands of Chios, which has just destroyed one of the most special assets in the natural world. More than half of the island’s mastic trees are reported to be smoking wrecks.

When Greece is being squeezed for every asset it can sell, what power in heaven could allow the ruin of the Chiote trees, the greatest mastics in the world? In antiquity the gum of these trees is believed to have been used as a filling for teeth. It was also used as a resin with a bracing flavour. In the early modern period Venetians and others fought for possession of the few hillsides on which the evergreen trees grew. Even nowadays mastic toothpaste is a prize to be found in Chios’s shops and airport stores. The trees are highly localised and their farmers had just been preparing to collect the resin, which they tap yearly from the trees’ trunks. Fanned by wind a fire then swept across from the forest around Nea Moni, the island’s world famous Byzantine church. The ancients believed that fires could begin spontaneously from branches that rubbed together, or if not, from one of Zeus’s thunderbolts.

Near Nea Moni I expect the culprit will turn out to be a discarded Greek cigarette. After the hot dry summer the flames were unstoppable and swathes of the centuries-old mastic trees have now been destroyed. Slow growing and tenacious, they are not trees that can regenerate like olives from a stump. Thanks to our fellow humans they have gone forever, in a single night.

Robinia pseudoacacia Frisia©GAP Photos

Robinia pseudoacacia Frisia

Here in Britain something is gravely wrong with the Robinias, which we misname “acacias”. Thirty years ago I picked on the golden leaved Robinia pseudoacacia Frisia as one of my top trees for a modern garden. Its leaves are not the earliest to appear in spring and the branches can be brittle in sites exposed to strong wind. The colour of the leaves is one that I personally find so cheerful, turning from yellow to luscious green-yellow as the season advances. Suddenly since June these golden trees have been dying without warning. Their yellow leaves start to drop and then in a week the branches turn out to be dead from top to bottom. Robinia Frisia has been known for nearly a century but it has suddenly decided to take its leave. Does any fellow-suffering reader know what the cause is or have any practical advice that will control it? Meanwhile the tree is no longer one to plant.

I have long been a fan of larch trees, the trees for shelter belts and boundaries. They are not easy to underplant but they break high winds and have a range of colour in autumn and in their young twigs. Now their fan club is in retreat. The trees are linked to the spread of the killer phytophthora disease, which also attacks azaleas and fine rhododendrons. This disease spreads by wind and is particularly prone to proliferate on larch trees. Belts of larches in or near publicly owned gardens are being ordered to be felled in an effort to curb phytophora ramorum’s spread. The cull seems drastic to those who are not statistically minded or who hope that the disease may check as fast as it was first diagnosed as a problem. Meanwhile we must not plant a line of larches until the condition is controlled.

At least we know all too well what is now endangering Europe’s palm trees. It is a proliferating red palm weevil that arrived from south-west Asia in the new millennium. In Spain’s Marbella the mature palms in the city have already had to be felled. The Balearic islands have become infected with it too and there are frantic communal efforts to contain it. The weevil loves to eat the elegant fronds of the Canary Palm, the tree in so many pictures of the region’s mild and sunny landscape. The best of these trees are as old as Chios’s mastics and also very slow growing. The weevil then moves onto the date palm and is even more prolific than the bunny rabbit. It has up to four birth cycles a year and each female lays about 200 eggs at a time. The young grubs then bore into the palm tree’s trunk and weaken it with long tunnels. They also eat away the young growth. The weevil has now been found in Italy and above all in southern France. Communal action has been called for to prevent the devastation of all the 20,000 palms along Nice’s seafront. I encountered the campaign there this April and have followed up on it in two important articles in the April number of The Mediterranean Garden, journal of the Mediterranean Garden Society. The mayor and commune of Nice have been admirably active and anyone concerned for nearby palms in private care should link up with the local scheme for prevention and elimination, described in outline in the Mediterranean Garden’s articles. A ban on the import of palms into France has been demanded for the next three years. Chemical prevention is still a possibility but the schemes on offer have yet to be tested over the longer run. Meanwhile, garden designers are looking to Texas rather than Morocco for mature specimens to use in big landscape schemes.

Maples in Vermont, New England©Alamy

Maples in Vermont, New England

Here in Britain the conspicuous casualty is the apple crop. In many regions the trees have set little or no fruit. The reason is not the much publicised decline of the bee, necessary pollinator though it is. The cause is this year’s peculiar weather. Amateurs are blaming frost for ruining the blossom but the culprit is not so simple. Not only was May surprisingly free of sharp frost in the south except for one cold night. Early, middle and late fruiting apples are all affected, although their flowering times differ and one sharp night will not hit them all. The cause was not a sudden bud-drop. The damage has to have been done when the pollen has just become fixed on the flower’s female stigma and fertilisation is beginning. Damp conditions are fine at this critical point, experts tell us, but the extreme rains in mid to late May were another matter. The crop is more likely to have gone missing through heavy, prolonged rain than through one night below zero. It will be Golden Delicious from France in October, not Cox’s Orange Pippins in bulk from Kent.

I am sorry for this grim welcome to those of you returning to your home orchard, palm grove or island with hopes of a heavenly September. I have not even discussed oaks except to hope that their disease will SOD off. If an oak dies suddenly on you, then you know you have the sickness in the garden. A pre-emptive strike is the Ministry’s best answer at present. No gardener is going to fell an oak on the off chance of losing it later. Meanwhile, sit back, but never ever throw a cigarette away into the bushes while enjoying these last days of the season in a summer deck chair.

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