Passion among the plum trees: Some varieties develop fruitful relationships with their neighbours, others are prolific if you let them go piggyback, says Anna Pavord
In the case of 'Coe's Golden Drop', prolific means 14 plums. The position of each one of these fruit on the tree is as familiar to me as the sequence of stations on the London Underground map. I was more shocked by the loss (cause unknown) of No 15 plum last week than when Gloucester Road disappeared, temporarily, from the Circle Line.
The variety is named after Jervaise Coe, a market gardener in Bury St Edmunds, who raised it at the end of the 18th century. He was never sure who the parents were, but he thought that they were most likely to be greengage and 'White Magnum Bonum', which grew side by side in his nursery.
The fruit has the melting sweet flavour of a perfect greengage but intensified threefold. It matures late at the end of September and is lemon shaped, with a characteristic little bump at the stalk end. It has yellow skin and rich golden-yellow flesh. But it is what is euphemistically known as 'shy-fruiting', the meanest of all plums. That is why 14 can be interpreted as a triumph rather than a
Planted on its own, it would bear nothing, for 'Coe's Golden Drop' is one of several important plums that need a pollinator - a plum of a different variety growing nearby - in order to set fruit. 'Rivers' Early Prolific', 'Jefferson' and 'Kirke's Blue' are equally hopeless on their own. But the self-fertile types, even the paragon 'Victoria', do not have such a good flavour. And they, too, set better crops if they have other plum trees with which they can cross-pollinate.
Climate also makes a difference. Generally, plums are more difficult to grow in the western counties of Britain than in the rest of the country. They like hot summers, hard winters and a late, short spring. The Caucasus and the countries round the Caspian Sea are their home and they have not forgotten it.
Situation is important, too. They need shelter from wind and as much protection as possible from late frosts. Late-flowering varieties such as the dual-purpose 'Oullin's Gage' have a better chance of escaping frost than the early flowering 'Jefferson'. The most succulent fruit comes from fan-trained trees planted against south-facing walls. Plums are too prolific in growth to make cordons or espaliers.
As with apples, trees are grafted on to different root stocks, which control their relative vigour. The most common is 'St Julien A'. Grown on this, a 'Victoria' plum will spread at least 15ft after about 10 years. Dwarfing root stocks are less common with plums than with apples, though there is one in use called 'Pixie'. It cuts down the eventual size of the tree by two-thirds or a half, but the tree needs richer soil and more cossetting than the same variety growing on 'St Julien A'.
Grafting is the horticultural equivalent of a piggyback. The graft borrows stronger legs than its own to do what it needs to do. But when you are planting, you need to be sure that the graft, which usually shows as a bump or a slight swelling on the trunk, is well clear of the soil. If you bury it, the top graft will try to grow its own roots and lose the benefit of the piggyback from its stronger companion.
There are still more than 80 different varieties of plum available to anyone who has space to plant. Where there is room for only one tree, I suppose it would have to be 'Victoria', which is not as fussy about its position as some other plums and crops well and regularly. In fact, it has a tendency to overcrop and, if you let it, will then want to rest the following year, like an enervated actor after a particularly stressful run of Hamlet.
Thinning is the way round this problem, leaving no more than one fruit every three or four inches. The tree sheds some fruit itself, usually in June when the stones are beginning to harden.
Where there is room for more than one tree, you must work on setting up the right relationships. A spread of early, midseason and late varieties seems a simple option, but check that you have chosen varieties which have the same, or overlapping, flowering times. This is vital if you are including varieties that are not self-fertile. Kind nurserymen, such as Scotts of Merriott, include all of this information in their catalogue, leaving you free to drool over the descriptions.
There are a few stumbling blocks to avoid. 'Jefferson' and 'Coe's Golden Drop' will have nothing to do with each other, even though their flowering times overlap. 'Cambridge Gage' will not help common greengage.
Then there is the pruning . . . First of all, if you want a fan, forget all those complicated strip cartoons that tell you in various shades of green which bits of the tree to keep and which to cut off. You can buy fans already trained with eight straight arms. Fix eight long bamboo canes to fan out from the centre of your fence or wall and tie the branches on to those. Keep them tied in as they grow.
You can allow other shoots to grow into more branches if you have space to fill, but all the rest of the shoots sprouting from this main framework need to be nipped out. This should be done in two stages. In July, pinch back all side shoots to about six leaves. These will be the shoots that will bear fruit the, subsequent summer. When they have fruited, cut back these sideshoots by half, to about three leaves. Any shoots that are pointing directly into the fence should be rubbed out entirely.
Fans are decorative and take up space in just two dimensions rather than three. However, because growth is restricted, you cannot expect more than 30lb of fruit from each fan. A free-standing tree will produce more fruit: 50lb after 10 years, twice as much again when it reaches
Ordinary trees require very little pruning. Just take out dead wood and thin growth if it becomes overcrowded. Any cutting should be done in late spring or summer. This reduces the risk of silver- leaf spores infecting the tree.
Silver leaf is the most serious of the plum's problems and there is no cure. You can cut out infected branches and hope, but if more than a third of the tree is blighted, you will be lucky to see it
Bullfinches are at least a more decorative problem and not terminal - except to your hopes of an epicurean dessert. Robert Fish, head gardener in the 1860s at Putteridge Bury Park, in Bedfordshire, was not so forgiving about bird damage. He sprayed all of his fruit trees with a thick wash that was made from soot, lime, clay, cow dung and salt. This, he reported laconically, 'sticks on pretty well by the help of the clay and the cow dung.
'So long as the buds are thus crusted,' he continued, 'the buds will hardly be touched by any bird.'
It is the thought of the heavily crusted junior gardeners who no doubt had to carry out this spraying that worries me.
Plum trees (best planted in late autumn) are available from Keepers Nursery, 446 Wateringbury Road, East Malling, Kent ME19 6JJ (0622 813008), which has the largest selection in the country. A good choice is also available from: Scotts Nurseries, Merriott, Somerset (0460 72306); Deacon's Nursery, Moor View, Godshill, Isle of Wight PO38 3HW (0983 840750); J Tweedie Fruit Trees, Maryfield Road Nursery, Maryfield, near Terregles, Dumfries (0387 720880). All do mail order.
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