AN INTRODUCTORY GUIDE
Hear the plum: may your hopes rise fresh and strong like the young shoots that spring from my ragged trunk, and may your life flower with loveliness.
Alfred Loelm, from "A Gift of Japanese Flowers"
The genus Prunus includes some of our most useful and beautiful cropping trees - almonds, cherries, apricots and peaches are among the best known. Yet, arguably, none is more versatile than the humble plum.
In common parlance and in different cultures, plums have been known over the years by a number of names: plum, prune, bullace, damson, date plum, greengage, mirabelle, cherry plum, sloe. Although this can easily lead to confusion, this diversity of names suggests the huge variety offered by this magnificent species. In size and shape, the fruit may be large or small, round or elongated. In colour, they can be green, black, purple, blue, red or yellow. The plants themselves range from sturdy trees to spreading shrubs, with foliage that may be delicate or heavy-leaved. And, in the words of American plum-fancier, Pat Carter, plums "have a wider range of really great flavours than even apples". Plums also rival apples in their health-promoting properties, being rich in minerals and trace elements (including iron, calcium, phosphorus, magnesium, sodium and manganese) and containing vitamins B, C and E. They are low in calories, high in carbohydrates, low in fat, high in antioxidants.
DAMSONS
The damson is derived from Prunus x domestica var. insititia, the bullace. It has not been much developed by nurserymen and has all but disappeared as a commercial crop, probably because it has value only when cooked. This is a great shame, as anyone who has tasted a damson crumble would tell you, for this is a fruit with the most intense of flavours. As for the tree itself, it is compact, upright, relatively disease-resistant and exceptionally hardy. It likes winter chilling, doesn't require much in the way of pruning and, being partially self-fertile, will produce fruit without the aid of a pollinator. Damsons can cope with dry conditions, although they will produce plumper fruit if they get water in the period before harvest. The fruit should be allowed to ripen fully on the tree, after which they can be used for jams, jellies, hot puddings, spicy sauces, pickles and alcoholic beverages. Like many old varieties, the damson is becoming something of an endangered species. As such, it has become the subject of preservation work in the UK, particularly in Shropshire, an area once famed for its damsons. (The Shropshire Branch of the National Council for the Conservation of Plants and Gardens is the body responsible for this work.)
GREENGAGES
Like damsons, greengages are hardly grown at all as a commercial crop. They are, however, a wonderful fresh fruit, having an excellent flavour - better even than that of the plum, in the opinion of many - when picked ripe from the tree. The greengage is named after Thomas Gage, who brought the tree to Britain in the early eighteenth century. The greengage shares with the damson a liking for winter chilling and won't fruit at all in places with mild winters. It also prefers dry, sunny summers. Best pruned to an open vase shape, it has a tendency to bear fruit every other year, although this can be countered to some extent by judicious thinning of the fruit.
PRUNES
The prune is a type of plum selected specifically for its properties when dried. Cultivated in China for more than 3000 years, prune plums were brought to Europe by the Christian crusaders on their return from the Holy Wars. Today's prune plum is derived from the "Prune of Damas" (hence Damascus) scion. France became the undisputed leader in prune production up until the twentieth century. It was eclipsed by California in the 1930s. In the old days, the fruit used to be dried in the open air on beds of straw or on racks made of poplar. Nowadays, gas-fired ovens are used, heating the plums to 72 °C and reducing them to a moisture content of 21% (for storage) or 35% (for immediate consumption). Three kilograms of fresh fruit yields about 1 kg of dried prunes. Apart from their uses in cooking - well-known to all cooks - prunes are also of medicinal value. Culpeper recommends the prune to his reader for their ability to "loosen the belly... to procure appetite... and cool the stomach". Although, I suspect, not so much used for this (notorious) purpose these days, prunes are, as Culpeper suggests, an excellent natural remedy for constipation. They also work as a diuretic and can help those who suffer from gout or arthritis.
PLUMS
The plum is represented by two main types: the European plum (P. x domestica; P. insititia); and the Japanese plum (P. salicina). It is important to understand from the outset that these two types cannot cross-pollinate.
European plums
The European plum is a hardy tree and moderately long-lived. It requires a longer period of winter chilling than the Japanese varieties and grows quite slowly. European plums benefit from ample supplies of organic matter and need plenty of potassium and phosphorus to put on good growth. Most varieties are self-fertile, although they will produce more fruit if they have a suitable pollinator in close proximity. Trees can be pruned to a central leader or open vase shape. If necessary, fruit should be thinned, leaving a gap of 2-3 inches. Well-known varieties of European plum include: Stanley; Victoria; Mirabelle, Hanszwetsche (this is used for the production of schnapps).
EUROPEAN
| Name | Season | Pollinator | Description, Uses |
|---|---|---|---|
| Angelina Burdett | Early, mid |
Greengage President |
Purple skin, yellow flesh. Fresh, drying, preserves |
| Coes Golden Drop | Mid |
Greengage President |
Yellow skin, yellow flesh. Fresh. |
| Greengage | Mid |
Coe's Golden Drop Angelina Burdett |
Green skin, yellow-green flesh. Fresh, drying, preserves. |
| Luisa | Mid | Self-fertile | Yellow skin, yellow flesh. Great eating. Disease resistant |
| Damson | Mid, late | Self-fertile | Blue-black skin, green flesh. Preserves. |
| Stanley | Mid, late | Self-fertile | Blue-purple skin, green-yellow sweet juicy flesh. Drying |
| Victory | Late | Stanley | Blue prune plum. Also good fresh |
JAPANESE
| Black Doris | Mid, late |
Duffy's Early Jewel Elephant Heart Santa Rosa Billington |
Indigo skin, crimson flesh. Fresh, preserves, bottling |
| Elephant Heart | Late |
Santa Rosa Burbank Sultan |
Purple skin and flesh. Eating and preserving |
| Billington | Early |
Black Doris Wilson's Early |
Crimson skin, scarlet flesh. Bottling, cooking, jams. |
| Duffy's Early Jewel | Early |
Self-fertile Red Doris Santa Rosa |
Crimson skin, yellow flesh. Fresh, preserves. |
| Santa Rosa | Early |
Duffy's Early Jewel Omega |
Pink-red skin, yellow flesh with pink streaks. Good eating. Thrives in most areas. |
| Sultan | Early, mid |
Santa Rosa Elephant Heart Black Doris |
Crimson skin, red flesh. Juice, fresh, bottling. |
| Satsuma | Mid | Santa Rosa | Blood-red skin and flesh. Eating, juicing, bottling, preserves. |
| Wilson's Early | Very early | Red Doris | Red skin, yellow flesh. Fresh, preserves. |
| Burbank | Early, mid |
Partially self-fertile Santa Rosa Duffy's Early Jewel |
Red skin, deep yellow flesh. Good fresh. More cold tolerant than other Japanese plums. |
Japanese plums
Despite the name, these plums originate from China. Japanese plums generally produce larger rounder fruit than their European cousins. They also tend to ripen earlier, which is one of the reasons why they have become important commercially. (The New Zealand figures for 1978 were 305 hectares of plantings, of which 53 hectares were in Central Otago.) They are more precocious and vigorous, which means that they do not require so much fertilizing. Japanese plums will bear fruit after 2 years, as opposed to 3-5 years for European plums. These benefits come with considerable drawbacks, however. Japanese plums require more pruning and thinning. They are also less tolerant of poorer, heavier clay soils than European plums. Because they bloom early, they are particularly susceptible to frost. Ideally, they will be in a location free from frost by early September. The best conditions for good fruiting are dry, stable spring weather. Japanese plums are very juicy, which makes them sometimes very messy to eat fresh. Apart from their value as a fruit for eating, they also make good preserves. Many of the best-known varieties of plum - such as Black Doris, Santa Rosa, Omega (syn. George Wilson), Satsuma and Shiro - are Japanese plums.
Almost without exception, Japanese plums require cross-pollination. The following table, borrowed from the latest copy of OrganicNZ magazine (May/June 2007, Vol.66, No.3), should provide some basic guidance for both European and Japanese varieties. (Note: if space is short, you can, of course, always graft both the desired cultivar and its pollinator on the same rootstock.)
CONCLUSIONS
Plums certainly deserve a place in our gardens although they are fussier in their habits than such die-hards as apples and pears. European plums will not flourish without winter chilling (700 hours below 5 °C annually); Japanese plums need less chilling, but are frost sensitive (!). All plums should be planted for the sun (at least 8 hours full sun per day) and free air movement. The trees are pollinated by bees, bumble bees and (less successfully) by some other insects. Good shelter will encourage visits by hive bees.
Plums can be propagated by rooted cuttings, although grafting is usually more successful. Standard rootstocks are peach or Myrobalan cherry (P.cerasifera), the latter being much better suited to heavier soils.
Plums are susceptible to all manner of pests (mites, aphids, scale moths, caterpillars, etc.) and diseases (brown rot, blossom blight, rust, etc.). Silverleaf is probably the most serious risk. For full details, consult a standard guide. (Warning: this can make for depressing reading!) Birds will always tell you when the fruit is ripe! Early buds are also sometimes favoured by our feathered friends. For those interested in organic approaches, garlic is said to help repel pests; seaweed spray can be applied after fruit set; aerated compost teas may also provide some help against disease. But, remember, if all else fails, plums make for excellent firewood.
Andy Barratt
From the Coastal Otago Branch NEWSLETTER No.120 June 2007