Soil and Situation. Plums And Damsons succeed best on rather rich, loamy land. Plums and damsons require more nitrogen than apples and are therefore less suitable for ,grass orchards, though certain vigorous varieties, such as Blaisden Red and Pershore, succeed. Lime is beneficial. Sour, poor, and dry, sandy soils are unsuitable.
Plums flower early and are, in consequence, unsuitable for very exposed places in which the blossom is usually destroyed or fails to set. Choice dessert varieties may be trained against sunny walls. Some kinds, such as Belgian Purple, Czar, Oullin’s Golden Gage, Rivers’s Early Prolific, and Victoria, are also suitable for north walls.
Planting. This may be done at any time from late October till mid-March. Details are the same as for apples. Fan-trained trees should be 15 ft. apart.
Forms of Training. Plums are grown as cordons, fan-trained trees, bushes, half-standards, and standards. Cordons are not recommended as the very restrictive pruning necessary may cause bacterial canker. Choice dessert varieties, and particularly gages, should be fan trained against walls. The more vigorous, free-fruiting varieties, especially cooking plums and damsons, make excellent standards.
Pollination. Many varieties are completely self-sterile, while others set a very poor crop with their own pollen. Such should be planted with another variety of plum or damson that flowers at the same time. Self-fertile varieties may be planted alone.
Pruning. Bushes and half- and full standards are treated very lightly after the first few years, during which the frame-work of the tree is built up in the same manner as that of an apple. Subsequently, all dead wood and any large branches that have been damaged, or are diseased, should be cut out in June. Further thinning of poor or ill-placed branchlets is done in late summer after the crop has been gathered. Leaders are shortened a little in March, to an upward-pointing bud for drooping varieties and an outward-pointing bud for those of upright habit.
All large wounds should be covered at once with Stockholm tar or a proprietary wound dressing.
Trained plums must be treated rather more severely. From June to August the tips of young side shoots are pinched out when they have made six to eight leaves. In September older shoots are shortened to fruit buds where these have formed. Leaders are shortened each September by about one-third of their length until the wall space is filled, after which they are cut right out.
Forming Fan-trained Trees. Maiden (i.e. one-year-old) trees are cut back in November to within 15 in. of ground level. The following spring about four new shoots are retained and trained equidistantly like the main ribs of a fan. The following November these main branches are shortened to about 15-18 in. each, and the thinning and training process repeated in the spring, with the result that the tree is provided with anything up to sixteen principal branches evenly spaced in one plane. The process may be repeated indefinitely until the whole available space is covered. Thereafter, pruning is the same as for established trees.
Thinning Fruits. This is usually unnecessary, except with choice dessert varieties against walls. Fruits on these may be reduced to one every 2 or 3 in. after stones are formed. A preliminary thinning to half distance may be given three or four weeks after flowering.
Picking. Should start as soon as the fruits are well coloured and juicy. Culinary varieties may be picked over several times, the first when the fruits are sizeable but still green. These can be used for cooking or bottling, so leaving more space for the remainder to grow. Plums cannot be stored but may be bottled or dried.
Routine Feeding. Nitrogen and potash are the two important elements but with more emphasis on the former than with apples. Give a good dressing of rotted dung (1 cwt. to 12 sq. yd.) each March, lightly forked in, followed by sulphate of ammonia, nitrate of soda, or Nitro-chalk, at 1 oz. per square yard in May, and sulphate of potash at 1 oz. per square yard in October. Every alternate October give, in addittion, basic slag at 6 oz. per square yard, or instead use fruit-tree fertilizer.
Routine Pest Control. Spray early each January with tar-oil wash. Cut out all dead wood or branches carrying silvered leaves before the end of July and paint wounds with Stockholm tar. Spray repeatedly with malathion if there is any sign of aphids.
Propagation. By budding in July or August exactly as for apples. Many stocks are used. Brompton is vigorous, suitable for standards and large bushes and is compatible with all varieties. Myrobalan B is vigorous and one of the most popular stocks for large trees but a few varieties such as Count Althann’s Gage and Oullins Golden Gage will not grow on it. Common Mussel and Common Plum are semi-dwarfing and suitable for small trees and fan-trained plums but some varieties will not grow on them. St Julien A and Pershore are moderately dwarfing and suitable for small trees. They are compatible with all varieties.
A few varieties of plum are best propagated by suckers, a method usually too slow for nurserymen. These are Blaisdon Red. Pershore. and Warwickshire Dronner
Varieties of Plum. Belgian Purple (CD), Aug.; Belle de Louvain (C), Aug.-Sept.; Blackbird (CD), Aug.; Black Prince
(C), July; Blaisdon Red (C), Aug.; Blue Rock (D), Aug.; Blue Tit (D), Aug.; Bountiful (D), Aug.; Bradley’s King (Damson) (CD), Sept.; Bryanston Gage (D), Sept.
Cambridge Gage (D), Aug.; Coe’s Golden Drop (D), Sept.; Count Althann’s Gage (D), Sept.; Cox’s Emperor (CD), Sept.; Cropper (CD), Sept.; Czar (CD), Aug.
Denniston’s Superb (D), Aug.; Diamond (C), Sept.
Early Laxton (C), July-Aug.; Early Orleans (C), July; Early Transparent Gage (D), Aug.; Evesham Wonder (C), Aug.
Farleigh Damson (Cluster or Crittenden) (C), Sept.; Frog-more Damson (C), Sept.
Gisborne’s (C), Aug.; Giant Prune (C), .Sept.; Golden Transparent Gage (D), Sept.; Goldfinch (D), Sept.; Green Gage
Jefferson (D), Sept. ; Jubilee (D), Aug.
Kirke’s Blue (D), Sept.
Langley Bullace (C), Oct.-Nov.; Late Orange (C), Oct.; Late
Transparent Gage (D), Sept. ; Laxton’s Gage (D), Aug. Marjorie’s Seedling (C), Oct.; Merryweather Damson (C),
Sept.; Mirabelle (C), Aug.; Monarch (C), Sept.-Oct. Oullin’s Golden Gage (CD), Aug.
Pershore (C), Aug.; Pond’s Seedling (C), Sept.; President (C), Oct.; Purple Gage (ReinetClaude Violette) (D), Sept.; Purple Pershore (C), Aug.
Reine Claude de Bavay (D), Sept.-Oct.; Red Magnum Bonum (C), Sept.; Rivers’s Early Prolific (C), July.
Severn Cross (C or D), Sept.; Shepherd’s Bullace (C), Oct.; Shropshire Damson (CD), Sept.-Oct.
Transparent Gage (D), Sept.; Utility (D), Aug.; Victoria (CD), Aug.-Sept.
Warwickshire Drooper (CD), Sept.; White Bullace (CD),
Oct.—Nov.; Wyedale (C), Oct.