PlumPrunus domestica

The plum is grafted on three common rootstocks: Saint-Julien A, the classic one, gives a half-standard or an open-centre bush of 4 to 5 m, sturdy on clay soil; Pixy keeps the tree to 3 m and suits the spindle or the small garden, but needs moist soil; Wavit, more recent, offers a vigorous and productive compromise. Myrobolan gives a standard for a meadow, vigorous and free with its suckers. The most natural form is the open-centre bush, with four or five spreading main branches that let the light in; the spindle calls for regular summer pinching. The plum trains badly, except as a fan against a wall for the greengages.

The situation is simpler than with the apple: Reine-Claude d'Oullins, Victoria, Opal, Mirabelle de Nancy, Quetsche d'Alsace and Belle de Louvain are self-fertile and crop on their own, better still with a neighbour. Reine-Claude dorée, Reine-Claude de Bavay, Kirke's and Prune de Prince need a pollinator from a compatible pollination group; Victoria or Opal, generous with pollen, fill that role for almost all of them. Mirabelles and quetsch plums flower later than the greengages and do not always pollinate one another across the groups. Bumblebees, active in the cool April weather, are the real pollinators: do not drive them away.

The plum's flowering, in early April, is the most exposed in the orchard: favour a sunny position, sheltered from east and north winds, out of frost pockets. Against a south- or west-facing wall, a greengage grown as a fan gives fruit as sweet as in Lorraine. The plum accepts a heavy, clay soil, even wet in winter, provided the water does not stand permanently; it fears dry sand far more. A pH of 6 to 7.5 suits it. Space 5 to 6 m on Saint-Julien, 3 to 4 m on Pixy, 8 m on Myrobolan, and keep 3 m from a hedge that would cast shade.

Dig a hole 80 cm square and 50 cm deep, keeping the topsoil and the subsoil separate. Break up the sides. Mix into the topsoil two or three spadefuls of mature compost and a handful of hoof and horn; the plum dislikes heavy feeding at planting, which gives soft growth and gummosis. In heavy soil, work in a little coarse sand and plant on a 15 cm mound. Drive in a 2 m stake before the tree, on the side of the prevailing wind, or two stakes joined by a crossbar for a half-standard. Let the soil settle for a week.

From November to March, outside frosty spells, plant bare-rooted: the plum takes very well this way. Puddle the roots in a slurry, set the graft union 10 cm above the soil, spread the roots out, fill in with fine soil, firm, water with 20 litres and mulch over a metre. A one-year-old maiden intended for an open-centre bush is cut back to 80 cm above four or five well-spaced buds; a young bush already formed is planted without pruning, or with a simple shortening of the main branches by a third if they are long and thin. Tie with a soft figure-of-eight tie. No fertiliser in the first year.

A plum on Pixy, or a dwarf plum such as Black Amber or the mirabelle Miragrande, will live in a 70-litre container, but it remains the least rewarding of the fruit trees in a pot: its fast growth exhausts the compost and its early flowering freezes easily on a terrace. If you do try, choose a self-fertile variety, Opal or Victoria, a compost-rich mix, watering every other day in summer and an organic feed in April and June. Bring the container in or wrap it in hard frost, and stand it outside sheltered from the wind in April. Repot every two years. Expect three kilos in the good years.

The first is to prune the plum in winter as you would an apple: the wounds run with gum, and silver leaf and canker move in. The second is to let a young Victoria carry its whole crop: its branches tear under the weight in August, and the tree then crops in alternate years for years afterwards. Many people also plant a Reine-Claude dorée on its own, without a pollinator, or in a frost pocket at the bottom of the garden. Finally, letting rootstock suckers come up around the trunk, especially on Myrobolan and Saint-Julien, weakens the tree: cut them off flush as soon as they appear.

For the first two summers, water every week in dry weather, 20 litres at the base, from May to August. On Pixy, keep to this rhythm for three or four years, as the rootstock tolerates drought badly. A shortage of water in June causes a heavy drop of young fruit; a sudden excess after a dry spell in August makes the ripe plums split. So water regularly rather than heavily all at once. A mature plum on Saint-Julien or Myrobolan makes do with Belgian rainfall, except in a prolonged heatwave, when a generous watering every ten days keeps the size up.

A 10 cm mulch over a metre across, renewed each spring, is enough, with two spadefuls of mature compost in March and a handful of wood ash for potash, which favours sugar and colour. The plum appreciates a slightly chalky soil: on acid ground, a dressing of magnesian lime every three years in autumn prevents deficiencies. Avoid fresh manure and nitrogen fertilisers, which push out wood, cause gummosis and attract aphids. On a standard, a meadow cut late and the animals grazing it provide feeding enough.

Form the open-centre bush in late summer, never in winter: in the first year, select four or five well-spaced main branches and remove the others; in the second and third years, shorten these branches by a third in August, to an outward-facing bud, to make them branch. After that, maintenance pruning is done once the harvest is over, in August or early September, in dry weather: take out dead wood, crossing branches and vertical water shoots, and open up the centre. Do not shorten the short lateral shoots, they carry the May blossom clusters. Seal large wounds with clay or grafting wax.

The plum overcrops in some years, then rests the next. Around mid-June, when the fruits are the size of a hazelnut and the natural drop is over, thin to one fruit every 5 to 8 cm on the large-fruited varieties, greengages, Victoria, Opal; mirabelles and quetsch plums are happy with a light thinning. Take off the misshapen fruits and those touching one another first. At the end of July, prop the overloaded branches with forked poles or a tie back to the trunk: a torn branch is an open door to canker. That is the price of 60-gram plums and of a crop every year.

Brown rot rots the fruit in grey rings in a wet summer: gather up every affected fruit and the mummies left on the tree in winter, prune to open up the crown, and do not damage the fruit. The plum moth is caught with cardboard trap bands on the trunk in July and with tit boxes. Against the green and the mealy plum aphid, soft soap in May and no nitrogen. Silver leaf, silvery foliage on one branch, means cutting 30 cm below the affected part and pruning only in dry weather. The August wasps are drawn off with a sugar trap set at a distance; the birds, with netting on Pixy.

In February, take off the mummies and paint the trunk with clay; do not prune. In March, compost and mulch. In April, throw a fleece over a young greengage on a frosty night, and let the bumblebees work. In May, watch for aphids and water if need be. In June, thin. In July, prop, fit the trap bands, start harvesting the early varieties. In August, harvest, prune straight afterwards in dry weather, burn the trap bands. In September, pick the quetsch plums. In October, gather up the fallen fruit and cut off the suckers. In November, plant and check the stake ties.

A dessert plum is picked at full ripeness, when the bloom is intact and the flesh soft near the stalk; a plum meant for a tart, a compote or drying is picked two days earlier, firm, so that it does not collapse in the cooking. Pick in dry weather, with the stalk, twisting gently: a plum that is pulled damages the May blossom cluster. Spread the fruit in a single layer in trays. For prunes, split, stone and dry at 60 °C in the oven or the dehydrator for twelve hours. The quetsch frozen in halves keeps its shape for winter tarts.