PLATYSTEMON CALIFORNICUS

H. A. A little-known hardy annual reaching about 1 ft., with light yellow, saucer-shaped flowers. Prefers a sunny position.

PLUM .

The higher up the plum tree grows,

The sweeter grow the plums. The more the cobbler plies his trade, The broader grow his thumbs..

Old Rhyme.

Plums are probably the easiest of all fruits to grow, unless planted in a frosty position, as they are early flowering. The precise type of soil is unimportant, although plums do not flourish on very acid or chalky land. The ideal soil is one with a good moisture-holding capacity as this ensures more vigorous growth and heavier crops.

Stocks. The main stocks are common mussel (comparable to Mailing IX for apples), common plum and Myrobalan B which is used for half standards. The Brompton stock produces trees which may be too vigorous for small gardens but is otherwise very satisfactory.

Plums are unhappy grown in restricted forms such as cordons and espaliers but give excellent results as fan-trained trees on walls, the fruits usually having an even better flavour than those from the open garden. The Damas C stock is often employed for trained trees.

Cultivation:

If the soil is deficient in lime, old mortar rubble, well worked in, will satisfy the trees for some years. Plant bushes and half standards about 15 ft. apart and fan-shaped trees on walls about 18 ft. apart.

Plums appreciate more bulky manure than apples. It is also helpful to give annual applications of ‘Nitro-Chalk’ or sulphate of ammonia, as well as sulphate of potash. These are, however, counsels of perfection as plum trees will often continue to crop freely with relatively little feeding.

Pruning:

Plums fruit on both one-year-old wood and older branches. Prune newly planted trees as for apples and pears. Established plums only require the removal of dead shoots and overcrowded branches in late spring. If pruning, is undertaken at this time, the risk of infection by silver leaf is reduced.’ Generally, it may not be acceptable to prune when a heavy crop of fruit is on the way, and pruning can then be postponed until after harvesting. Cover any large pruning cuts with white lead paint to prevent the entrance of fungus spores. Prune fan-shaped trees on walls in the same way as sweet cherries on walls, spacing the branches fan-wise about 1 ft. apart. In July laterals may be reduced to about the fifth leaf from the base, any further growth being removed in September.

Choice of Varieties:

Black Prince: a small, oval, black plum with a damson flavour. Can be used for cooking or dessert. Ready at the end of July or in early August and should be grown more widely as it is resistant to silver leaf and a heavy cropper. Sometimes listed as self-fertile but Merryweather Damson or Victoria may be used as pollinators.

Cambridge Gage: virtually identical with the true old greengage but a more reliable cropper. It is grown on a very large scale for preserving in Cambridgeshire but is equally valuable for immediate eating, being unsurpassed for flavour. Ready about the middle of August. Pollinators: Czar, Denniston’s Superb, Victoria.

Coe’s Golden Drop: a late plum ready at the end of September, but will keep for several weeks after gathering if carefully stored. Flavour delicious, as may be gathered from this eulogy: ‘… At its ripest it is drunk rather than eaten; the skin is rather tough, but between this and the stone floats an ineffable nectar. The stone and rather fibrous flesh may well be discarded with the skin, and, digestion unimpaired, we come to our port in beatific mood. Should it be port, I wonder? Perhaps rather a glass of Yquem is die benediction a supreme gage requires.’ Pollinator: Denniston’s Superb.

Czar: a very easy variety to grow. Season about mid-August. Very upright growth. Not a good dessert variety but excellent for cooking.

Liable to silver leaf but resistant to frost. Self-fertile.

Denniston’s Superb: a greenish-yellow gage ready about mid-August.

A strong grower and regular cropper. Self-fertile.

Early Laxton: the first plum to ripen, ready in late July, usually a week before Rivers1 Early. An exceptionally good culinary variety whether for tarts or jam, and also useful for dessert. Not a strong grower, sprawls and is very twiggy. Somewhat liable to bacterial canker. Fruits liable to drop quickly when ripe.

Pollinators: Denniston’s Superb, Early Transparent.

Early Transparent Gage: ready about mid-August. Compact grower and succeeds as a half standard. Liable to brown rot. Self-fertile.

Kirke’s Blue: in season about mid-September. Ranks with Cox’s Orange Pippin in apples and Doyenne du Cornice in pears as the variety par excellence for the connoisseur. Like the latter, it is an irregular cropper.

Needs a sheltered position and is best grown alongside a wall.

Pollinators: Czar, Marjorie’s Seedling.

Marjorie’s Seedling: suitable for both dessert and culinary purposes.

Starts to ripen in September, continuing into October. Resistant to bacterial canker. Self-fertile.

Merryweather Damson: a first-class culinary variety in season from early September well into October. A very strong grower and heavy cropper.

Excellent for bottling. Self-fertile.

Reine Claude de Bavay: a very fine late variety for dessert, ready at end of September or early October. Does well in the north, especially against a south wall. Usually regarded as self-fertile, but Merryweather Damson or Victoria would be good pollinators.

Victoria: in season about mid-August. Suitable for dessert, bottling and jam, but of indifferent flavour unless fully ripe. Of spreading habit with brittle branches and liable to break down with weight of crop unless thinned. Liable to silver leaf and bacterial canker. Self-fertile.

Insect Pests:

Red Plum Maggot or Plum Fruit Moth. A very common pest in Cambridgeshire, Kent and the south of England generally, the red caterpillar or maggot being found in the fruits from late June onwards. Entry is usually made near the stalk and the hole is frequently covered by a drop of gum which extends into the flesh of the fruit. The maggot is often found near the stone.

Treatment: Thorough winter washing with tar-oil or DNC petroleum gives some control. The maggots often shelter in cloth or sacking used to prevent stakes or other supports from chafing the bark, and these should either be removed and burned or given a thorough drenching with tar-oil winter wash. A Pyrethrin emulsion may also be applied about mid-June.

Leaf Curling Plum Aphid and Mealy Plum Aphid. Symptoms: The black eggs are laid in autumn on twigs of plums and damsons, hatching out in February and March. The young aphids suck the sap from leaves and blossoms, causing severe leaf curling and stunted fruitlets. After midsummer they migrate to certain weeds and herbaceous plants, including the forget-me-not, returning to the plum in early autumn for egg-laying.

The mealy plum aphid begins operations in early June — later than plum leaf curling aphid — infested foliage showing a white mealy covering under which clusters of aphids may be found. There is no leaf-curling.

Treatment: The usual tar oil winter wash applied in December or early January prevents attacks of both species. Nicotine or gamma-BHG are excellent spring washes, but must be applied thoroughly and before leaf-curling becomes serious.

Plum Sawfly. Symptoms: Damage caused by this insect closely resembles that of the apple sawfly. Eggs are laid in the flowers and the caterpillars enter the young fruits, feeding on the flesh. Several fruits may be entered before the caterpillar reaches maturity, a wet, black mess extending from the point of entry. Infested fruits drop to the ground while still small.

On maturity, the caterpillar drops to the ground, overwintering in the soil and emerging as an adult sawfly the next spring. Czar is a highly susceptible variety.

Treatment: Spray with a BHC preparation 2—3 days after petal-fall and again a week later.

Give a thorough drenching spray, which will also help to check other caterpillars.

Fruit Tree Red Spider. Red spider can be a very serious pest. The life history is described under APPLE — type of damage being virtually the same. Czar is again susceptible. Winter spraying with DNC petroleum destroys the eggs while the mites are controlled by a lime-sulphur or derris application about ten days after petal-fall and again in mid-June.

Fungus Diseases.

Bacterial canker. Symptoms: This disease, though very serious where it occurs, is found more frequently in commercial orchards rather than gardens. The same organism is responsible for bacterial canker on both plums and cherries. With plums, cankers occur mostly on the stems, whereas on cherries, branches are more liable to infection. Infection probably takes place as the result of bark damage in autumn, though the cankers may not be apparent until spring. Leaves turn yellow, growth is stunted and the foliage eventually withers. Die-back often follows on bacterial canker.

Susceptible varieties: Czar, Burbank’s Giant Prune, Early Laxton, Laxton’s Gage, Victoria.

Resistant varieties: Marjorie’s Seedling, Utility, Denniston’s Superb. No really satisfactory spray treatment has yet been found, but spraying with Bordeaux mixture after petal-fall may help.

Brown Rot. This disease is described under APPLE — symptoms being very similar and control measures precisely the same. Plum Leaf Rust. Symptoms: During the summer leaves may show small, yellow spots on the upper and brown on the under surfaces. Severe attacks may cause premature leaf dropping and consequent reduction of crop. Apply Bordeaux mixture as for bacterial canker control. Anemones are host plants for the fungus and should not be grown near plums. Plum Silver Leaf. Symptoms: This disease attacks all tree fruits, though plums are the most susceptible. Leaves develop a silvery sheen, caused by a layer of air under the surface. A brown stain is found in the wood of affected branches, which eventually collapse and break off. The silvery leaves are not infectious, as the spore stage develops only on dead wood. Victoria is very susceptible and Black Prince resistant. Treatment: No effective spray treatment has yet been found. Affected trees often recover, particularly if kept in a vigorous state by generous manuring. All infected branches should be cut away and burned, taking care that the cut extends beyond the brown stain. All dead wood must be removed and burned. Infection does not appear to take place during June, July and August, so that pruning should take place at this time, or after the crop has been picked, instead of in December or early January. All wounds and pruning cuts should be painted with white lead paint.

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