Plums
“What is more mortifying than to feel that you have missed the plum for want of courage to shake the tree?”
Logan Pearsall Smith
When we think of plums, we usually think of the European plum, of which Victoria is an example, but there are actually many different types of plum. Damsons, bullaces and mirabelles (or Myrobalan plums) are all botanically distinct forms of plum.
The damson is a small, tart plum that can be grown where other plums would struggle.
The origins of the European plum (Prunus domestica) are obscure: it is thought to have derived from naturally occurring hybrids in the Caucasus area. Hundreds of cultivars have now been bred, including the greengages, which are a separate group within P. domestica. European plums include both cooking and dessert varieties, ranging from the dry acidity of Blaisdon Red through to the toffee-apple sweetness of Kirke’s Blue or Jefferson.
Damsons, bullaces and mirabelles all fall into the category Prunus institia; they are smaller and tougher trees than European plums and somewhat easier to grow. Damsons are small blue-black fruits with a rich flavour and slightly spicy taste. They are quite sharp and usually used for cooking. Mirabelles, or cherry plums, actually look like large cherries on the tree, in shades of red and yellow. They are generally fairly sweet, perfect for jam making. Bullaces are seen as a wild fruit in Britain. They are small, acid plums that need to be cooked with plenty of sugar.
At the other end of the plum spectrum from the tart bullaces and damsons are the more refined, sweet greengages. Generally, the more refined the fruit is, the more temperamental it is, so while damsons and bullaces are tough enough to grow in hedges, greengages need a carefully chosen site and plenty of pampering.
THE WESTMORELAND DAMSONS
In the former county of Westmoreland, now part of Cumbria, the Lyth and Winster valleys were home to large orchards of damsons, dating backto the 1700s. The fruits were sent to Lancashire jam factories for making damson jam. In return, charabancs filled with sightseers would visit the valleys in April to admire the wonderful blossom. It is thought that damson skins were used to dye soldiers’ uniforms at one time.
The Westmoreland Prune, one of the most widely planted damson varieties in the former county of Westmoreland.
Damson Saturday was a local festival in the area, with its heyday between the two World Wars. The area around Kendal was famed for its carts and stalls selling the local damsons. The Second World War saw the demise of the damson trade, as manpower and sugar were in short supply. The Westmoreland Damson Association was formed in 1966 to preserve the damson orchards and encourage the use of the fruit. Damson Day is still held each year to promote the remaining orchards and their produce.
The history of plum growing in Britain
The history of plums is more complicated than the history of other fruits, because there is not just one fruit that we can call a plum. The European plum is thought to have derived from crosses between the sloe (Prunus spinosa) and the cherry plum (Prunus cerasifera). It seems that it spread to Britain from the Mediterranean region, even before the Romans grew it here.
Damsons originated from Damascus in Syria, while bullaces were a native of Britain, their remains having been discovered at Iron Age settlements. Cherry plums, like many fruits, seem to have originated in the Caucasus. Over time, boundaries have become blurred, but these divisions of plums are still meaningful today.
The thousand years after the Romans left Britain saw few advances in plum cultivation; it was largely monasteries that grew plums and perpetuated the few varieties known. Plum growing was reinvigorated by Henry VIII and his fruiterer, Richard Harris, who planted new varieties brought from Europe. In the seventeenth century new types of plums arrived in Britain, such as the German prunes and the reine claudes (later known as greengages), which arrived from France.
By the nineteenth century, deliberate breeding was being carried out in nurseries, the most famous being Rivers of Sawbridge-worth. Varieties that we still grow today, such as Early Rivers, Czar and several Transparent gages were bred there, while other cultivars were brought in from abroad. Despite all the effort put into breeding new plums, the most famous plum of all, Victoria, was discovered as a chance seedling in 1840.
By the twentieth century, research stations such as Long Ashton and Merton had largely taken over breeding from nurseries. Garden cultivars such as Severn Cross, Thames Cross and Merton Gem were the result of this breeding. Many varieties, such as Opal and Sanctus Hubertus, have been brought to Britain from abroad.
Cultivation of plums
There is a wide range of types of plum, some much more demanding of favourable conditions than others. Greengages fruit and ripen well only in the most favoured locations, while damsons and bullaces will thrive in harsher conditions where other plums would fail.
Plums are susceptible to silver leaf and bacterial canker, both damaging diseases that can seriously damage or even kill trees. It is important to pay attention to correct pruning times and techniques, in order to keep these diseases at bay. Choosing disease-resistant varieties (see Appendix 4.3) will also help to keep your orchard healthy. Some varieties are prone to overcropping, leading to broken branches, which not only disfigure a tree but are an access point for disease.
For details of pest, disease and other problems with plum trees, and how to deal with them, see Chapter 9 (pages 153-5). See Chapter 2 (page 33) for information on root-stocks.
Plums prefer a continental climate – that is, a cold, dry winter followed by a warm, dry spring and a hot summer. In Britain, it is only really the south-east of England that can offer such conditions. However, plums will tolerate less favourable climates so long as the soil is to their liking.
The ideal soil is a deep, well-drained, but moisture-retentive loam. Although they detest waterlogging, plums do need a good supply of moisture. For this reason, thin, shallow, or sandy soils will need considerable improvement with organic matter if they are to grow plums successfully. Clay soils are fine as long as the drainage is not compromised.
The addition of manure is helpful because it will aid moisture retention as well as feeding the trees. Plums prefer a slightly acid soil, a pH of 6 to 6.5 being ideal. Lime-induced chlorosis can be a problem on highly alkaline soils. Plums do not enjoy chalky soils, especially where they are thin. Reasonably fertile soils are needed to grow plums: they require good levels of nitrogen to fruit well, but have less need of potash and phosphorus than do some other fruits.
Plums need a sunny, sheltered position to perform well. This is particularly important at blossom time, because they flower early in the season (March to April), when cold, easterly winds can be a problem. Plums are pollinated by bees and other insects that need the encouragement of a sheltered situation at this time of year. Some cooking plums, such as Czar and Pershore, are capable of fruiting well in a slightly shaded position. Damsons and bullaces will also produce decent crops in light shade.
Plum blossom is susceptible to damage by frost. If you are growing plums in an area prone to damaging frosts in late March and April, it is worth choosing late-flowering varieties or those with frost-resistant blossom (see Appendix 4.2). If hard frosts threaten at blossom time, you can protect the blossom with hessian, thick fleece or sheets, keeping the protective material away from the flowers with bamboo canes.
Areas with high rainfall (over 100cm [3'3"] a year) can be problematic for plums, giving rise to higher incidences of bacterial canker and fungal diseases such as brown rot, as well as bringing an increased likelihood of waterlogging.
In essence, plums will do best in a warm, sunny, sheltered location, with deep, fertile soil. However, some are much less fussy than others. Damsons, bullaces and some varieties of plum will grow well in less-than-ideal conditions and areas of high rainfall. In general, early-ripening varieties have less need for the perfect location, whereas late-ripening dessert varieties need as much sun and warmth as possible in order to fully ripen the fruit. Training plums against a wall can improve the warmth, shelter and drainage of a less favourable location.
Feeding and watering
Plums require a good supply of nutrients, particularly nitrogen, although it is also good not to overdo the nitrogen because this will lead to soft, sappy growth that is more prone to attack by pests. Pelleted chicken manure, or blood, fish and bone applied in February will be sufficient, although mulching with manure or compost in the spring will not only add nutrients and organic matter but also help to preserve soil moisture.
Although plum trees appreciate good levels of soil moisture throughout the year, it is unlikely that established trees will need watering in the conditions encountered in the British Isles. Young trees may need watering in dry seasons while establishing. It is worth checking wall-trained trees regularly, because the soil at the base of a wall can dry out quickly.
Pollination
Many plum varieties are self-fertile, meaning that only one tree is needed to obtain a reasonable crop. However, all varieties will produce heavier crops if a suitable pollinator is provided. Some varieties are described as partially self-fertile, meaning that they will set a limited crop on their own, while others are self-incompatible (or self-sterile), meaning that they need another suitable plum tree to ensure pollination. If space is limited, you can get away with one self-fertile tree; otherwise, planting varieties that will pollinate each other will give you heavier crops.
Plum blossom.
Like most fruit, plums are divided into different flowering groups, depending on their time of flowering. In order to pollinate one variety you need to choose a variety from the same group, or an adjacent group. Dennis-ton’s Superb (early-flowering), Victoria (mid-season) and Oullin’s Gage (late-flowering) are all varieties that are known to be good pollinators.
Fruit thinning
Some varieties will produce very heavy crops in good years. This can lead to broken branches, small fruit and less flavoursome crops. Thinning can be carried out from late to mid-July, after the June Drop (see page 41), ideally leaving one fruit every 5-10cm (2-4") apart, depending upon the size of fruit. Branches bearing large crops can be supported with props, or by maypoling (see pages 95-6), to avoid the branch breaking.
Plum varieties
As with most fruits, disease resistance is an important factor in choosing suitable plums to grow. Get this right in the first place and you will avoid sickly trees later on. It is far better to grow disease-resistant trees in good conditions than to try to control diseases on unhealthy trees.
Victoria, for example, is by far the most popular plum, but this does not make it the best plum to grow. It does have advantages, such as being heavy-cropping, frost-resistant, self-fertile and a good pollinator. Its flavour is pleasant and it is a good plum for jam and cooking, as well as for dessert use. Yet it also has many drawbacks, particularly its susceptibility to bacterial canker and silver leaf. Its heavy cropping is actually its Achilles heel, in that it tends to crop too heavily unless it is thinned and/or propped. Broken branches are a familiar sight on Victoria plum trees, providing a point of entry for disease.
Kirke’s Blue is reputed to be the best-tasting plum, but it crops lightly.
There is, of course, no perfect plum: choosing the best varieties for you to grow is a matter of compromise between many different factors. For example, Kirke’s Blue is a wonderful-tasting plum, but crops only lightly.
Dessert plums
A dessert plum is one that can be eaten straight from the tree. The deliriously sweet greengages are also included here. Although plums do not keep for long, the season can be extended by choosing a range of cultivars that will provide a succession of fruit over a long period.
Recommended varieties
Many plum varieties are listed as dual-purpose, being suitable for both dessert use and cooking. The varieties given here are those known as good-quality dessert plums. Plums will only keep for a short time, so there is no ‘season of use’ information.
Varieties are listed in order of their picking date.
* Where no details are given on pest and disease resistance, this is because information is not readily available for these varieties. This is particularly the case for the less common varieties.
Although many plums are considered to be dual-purpose, culinary varieties have a distinct tanginess, being low in sugar and high in acidity. Some of the varieties with dry flesh, such as Yellow and Purple Pershore and Blaisdon Red, are particularly good for making jam. As with dessert varieties, it is possible to select varieties that will prolong the season, from Early Rivers, starting in late July, through to Marjorie’s Seedling, which will still be cropping in October.
Recommended varieties
These are varieties best known for their culinary qualities. Blue Tit and Reeves, both included here, are dual-purpose plums but are perhaps better known for their culinary value than as dessert plums. There is no ‘season of use’ information here because plums will keep for only a short time.
Varieties are listed in order of their picking date.
* Where no details are given on pest and disease resistance, this is because information is not readily available for these varieties. This is particularly the case for the less common varieties.
Damsons and bullaces are much tougher than other plums; they will tolerate conditions that other plums would turn their noses up at, growing in any reasonable soils that are not waterlogged. They can therefore be grown all over Britain without difficulty They suffer much less from diseases than other plums (most are resistant to silver leaf), but are still susceptible to the blossom being damaged by frost.
Recommended varieties
All damsons and bullaces will grow in wet conditions and in northern Britain, and are relatively free of pests and diseases. Most are resistant to silver leaf. Shropshire Prune, Merryweather Damson and Farleigh Damson are known to be well suited to exposed locations.
Specific information on pest and disease resistance in general and, for the less well-known fruits, on suitability for different conditions, is not readily available. Varieties are listed in order of their picking date.
Mirabelles
Also known as cherry plums, mirabelles are small round plums, mostly yellow or red, that are good for cooking and jam. They can also be eaten fresh when they are fully ripe. In Britain, they do best in the east of England, where they are often seen growing in roadside hedgerows, depositing their colourful fruit on the road in August. They will tolerate a little shade.
Most mirabelles are not included in the normal pollination groupings for plums because they flower earlier in the year. This makes the blossom very susceptible to frost damage. They are all self-fertile or partially self-fertile. Mirabelles are sometimes grown as fruiting windbreaks.
Trees are often sold simply as cherry plums, but there a few improved varieties. As with many damsons and bullaces, little detailed information on specific varieties is available.
Mirabelle (cherry plum) blossom.
Dittisham is a small village in South Devon that is famous for its plums. Legend has it that the local fishermen were called to salvage a wreck outside the harbour at the nearby port town of Dartmouth, but all they found on the ship were plums. It is likely that they were actually prunes rather than plums, because plums would not have kept long enough for a sea voyage. The fishermen, used to salvaging more lucrative cargoes, brought the prunes back to the village and planted them.
Although this might seem a fanciful tale, there are still plum trees growing on their own roots (as opposed to being grafted) all around the village. The main variety is the Dittisham Ploughman, whose name is said to originate from the German pflaumenn baum, meaning plum tree. There are also two local varieties of damson, the Dittisham Black and the Dittisham Damson. The plums are sold locally and also used to produce Dittisham Plum Liqueur.
The Dittisham Ploughman plum.
Pruning plum trees
Plum trees can be trained into a variety of different forms. The bush is one of the most common, because it is simple to maintain, requiring little pruning. The pyramid is a method of training that keep the trees smaller, but requires more work to keep their restricted shape. (The spindlebush is a similar form, but is mainly used only in commercial orchards.) Although rarely grown these days, large trees on Brompton rootstocks can be trained as standards or half standards. Fan training allows plum trees to benefit from the shelter of a wall, as well as making it easier to protect them against birds or frost. In more northerly areas, wall training allows a wider range of varieties to be grown. Cordons are suitable if you would like to grow a number of varieties in a limited space. This can, however, require a lot of work in order to keep them trained properly. Restricted forms are best grown on Pixy rootstock.
Pruning should be carried out with care, avoiding leaving any jagged wounds that can be a point of entry for silver leaf spores. Use a sharp pruning saw, follow good pruning practices (see Chapter 8, pages 104-5), and clean up any problem areas with a sharp pruning knife. It is best not to use loppers on plums unless they are able to make a clean cut. Branches should be pruned as early in their life as possible, so as not to leave large cut surfaces. Careful observation and forethought will allow many cuts to be made instead by ‘pinch pruning’ – pinching out growth using the finger and thumb – at an early stage.
The timing of plum tree pruning is largely determined by plums’ susceptibility to silver leaf and bacterial canker (see Chapter 9, pages 130 and 139). Silver leaf is a particularly serious problem on plum trees, which can lead to the death of trees and even the grubbing out of whole orchards. Silver leaf spores are released between September and May, so pruning needs to be carried out between June and August. The only exception to this is the formative pruning of young trees, which benefit from pruning when the buds have broken in the spring. Likewise, pruning in summer helps to keep plum trees free from bacterial canker, which can also be contracted through pruning wounds.
A wound paint (see page 140) should be used on any pruning cuts on plums that are large enough to be made with a pruning saw.
It is important to check ties regularly on plum trees, because any wounds formed by rubbing on the stake can allow silver leaf spores to enter the tree.
Plums fruit at the base of one-year-old shoots, as well as along the length of two-year-old and older growth. Fruiting gradually declines on older branches, so the aim of pruning plums is to encourage new growth that will fruit and to remove branches that are exhausted, cutting them back to replacement growth.
Plums are prone to developing suckers, which are best removed during the summer.
Formative pruning of a plum bush
Plum trees can grow vigorously when young. They will need careful training at this stage to prevent the tree from forming an unruly, upright tangle (see photo on page 98).
The bush is an ideal form for easy management and good productivity. However, even using the more dwarfing rootstocks, you will need a ladder to access the top of the tree -for pruning as well as picking.
A one-year-old plum tree is likely to have a number of laterals when planted during the winter. Leave these alone at this stage, unless it is vital to remove them to allow the fitting of the stake to the tree. Once the buds have broken, formative pruning can begin.
A bush tree will have a clear trunk of between 75cm and 125cm (2'6" and 4'2"), so firstly, cut back all laterals below this point by two-thirds; these will then be removed in the following year. Above this, select four or five strong branches, growing with a wide angle to the trunk, to form the main branches of the tree. These branches (or laterals) should be well spaced, so as not to compete with each other later in the tree’s life, and they should originate from all sides of the trunk in order to form a well-balanced tree. Any branches growing at a steep angle to the trunk should be removed, because they are weak and likely to break under the weight of a heavy crop when the tree is mature.
If there are not sufficient branches that have formed in the first year, wait until the second year to choose and retain these framework branches. Once sufficient branches have developed, remove the leader just above the topmost main branch.
Diagram 40 Formative pruning of a plum bush.
The laterals that are retained should be cut back by half to two-thirds to an outward-facing bud. On horizontal branches, or on varieties with a spreading habit, you will need to cut to an upward-facing bud to prevent the growth from becoming too weeping. Remember that, over time, branches are likely to become more horizontal with age, particularly under the weight of heavy crops.
During years 2 and 3, continue to prune in the spring, shortening the new growth of laterals or sublaterals by half. On weaker branches, half of the new growth can be removed, while stronger growth should be pruned more lightly. Any branches that are crossing, rubbing, misplaced or growing inwards should be removed. Likewise, strong vertical growth should be removed as soon as it is seen. If viewed from above (or below), the main branches should resemble a bicycle wheel in their pattern. During this period in the tree’s life, it is important to develop a strong, evenly spaced framework of branches.
This method of pruning continues until the crown of the tree is formed and the tree is fruiting well.
Pruning an established plum bush
The aim of pruning an established plum tree is to maintain its health and to ensure the formation of young wood, on which fruiting takes place. This is largely a natural process that just needs a little encouragement. Any dead, damaged or diseased wood should be removed. Strong vertical growth and misplaced or crossing branches can also be cut out. It is important to ensure that growth does not become too congested, preventing sunshine and light from reaching the ripening fruit. Where this happens, gently thin out crowded areas. It is good practice to keep the middle of the tree clear to allow air to flow and sunlight to penetrate.
Thin out heavy crops in early summer, preferably allowing 6-10cm (2.5-4") between fruits, depending on their size. If a branch has broken due to a heavy crop of fruit, prune it back to a junction with another branch. Do this immediately, whatever the time of year, so as not to allow a wound where silver leaf spores can enter. Where a heavy crop has developed, it is worthwhile propping any branches that look liable to break. Once a branch has been propped, consider whether you can prune to an upward-facing shoot so that the branch doesn’t become too low in the following season.
MAYPOLING
Maypoling is a method of supporting the branches of a tree using rope that is fastened from the top of a stake to the middle of a branch (see Diagram 14, page 96). It resembles the traditional maypole that children dance around in the springtime. This is particularly suited to pyramid trees, which already have a central stake in place.
Pruning a plum pyramid
Although they require more regular pruning than bush trees, plum pyramids are ideal for the smaller garden, or where space is at a premium. Grown on Pixy rootstock, they can be kept to 2-2.5m (6'6"-8') tall, depending on the variety.
A pyramid is a tree with the central leader intact and a number of horizontal branches radiating from the trunk. Careful pruning produces a shape like that of a traditional Christmas tree, where the lower branches receive plenty of light because the growth of the higher branches is restricted. The smaller size of the tree makes it more accessible for pruning, harvesting and netting. It can be difficult to train varieties with vigorous upright growth as pyramids, because the aim is to produce horizontal branches.
A strong 2.5m (8') stake is inserted at planting time (see Chapter 6, page 77). Do not try to do this after the tree has been planted, because you are likely to damage the roots. The stake stays in place throughout the life of the tree. Plums trained as pyramids can be planted more densely than would otherwise be possible on the same rootstock. On Pixy rootstock, 2.5-3m (8-10') apart is sufficient, while trees on St Julien A can be planted 3-4m (10-13') apart, depending on the vigour of the variety.
If you are starting with a maiden (one-year-old) tree, remove the central leader in the spring at around 1.5m (5') from the ground (see Diagram 41). Allow the top bud to grow on as the replacement leader, but rub out the three buds (or shoots) immediately below the top bud. If allowed to develop, these buds would go on to form branches at a steep angle to the trunk, competing with the leader. Removing the central leader encourages the formation and growth of laterals further down the trunk. Laterals emerging from the trunk can be cut back by about half (the upper and lower ones treated the same), to an outward-facing bud.
Diagram 41 Formative pruning of a plum pyramid.
In the spring of the second year, again prune back the (replacement) leader, removing two-thirds of last year’s growth, and again rub out the three buds (or shoots) below the top one.
The remainder of the pruning takes place during the summer. The laterals that were pruned last year will now have developed sublaterals; prune these back to around 15cm (6") long. Remove any new shoots emerging from the trunk below 40cm (1'4") high. Also, shorten any new laterals that have formed, by removing half of the new growth. The aim is to form a pyramid shape, with the lower branches dominant. The upper branches should not be allowed to shade out the lower branches, otherwise growth will become weaker on the lower ones. This process of shortening sublaterals (side shoots) during the summer helps to produce a small tree.
Once the tree is reaching maturity, the pruning continues in a similar vein, but with all pruning carried out in the summer months, apart from pruning the leader, which is done in the spring (see Diagram 42). The leader is still shortened by around two-thirds each year. A new leader will grow from a bud just below this pruning cut, but this growth will become weak in time. Any vigorous, upright growth is best removed, along with any dead, diseased or damaged growth and misplaced shoots. In time, growth will become congested, needing some thinning to allow air and light to penetrate. Continue to shorten the twiggy growth on the outside of the tree, in order to keep the tree compact.
Diagram 42 Pruning an established plum pyramid (summer).
Pruning standards and half standard plum trees
Plum trees planted on Brompton rootstock (vigorous) can be trained as standards or half standards. The formative pruning is similar to that of a plum bush, except that a taller clear trunk is needed, usually between 1.7 and 1.85m (5'8"-6'2"), and pruning of laterals can be a little less hard. This is a useful form for trees in an orchard with livestock, or for a specimen tree in a large garden.
Pruning a plum fan
This is an excellent method of training plums, with the wall providing warmth and shelter. It means that more temperamental plums, such as gages, can be grown in many locations that would not otherwise prove successful. Fans can also be grown in the open, in warm or sheltered locations, on a system of wires and posts. A plum fan on Pixy rootstock will take up a space about 3m (10') wide by 2m (6'6") high, while a tree grown on St Julien A rootstock will require a space around 3.5m (11'6") by 2.5m (8').
The ideal tree to plant is one with two strong laterals low to the ground and of roughly even vigour. In the spring after planting, the central leader is removed above these two laterals and the two laterals (or arms) cut back by one-third to an outward-facing bud. Tie these laterals to bamboo canes to support them and keep them straight. If one arm is less vigorous than the other, allow this one to grow at a more upright angle, which will increase its vigour. Eventually both arms should be at an angle of 40-45 degrees to the horizontal. Any less vigorous laterals, below the two selected, can be retained until the summer in case one of the selected laterals fails to grow successfully.
During the period of active growth in the summer, tie the new growth at the end of each arm to the bamboo cane (see Diagram 43). Because the laterals were cut back in the spring, side shoots (or sublaterals) lower down will be stimulated. Keep the best placed of these to form new ribs that will fill in the space on the wall. Ideally there will be two above and two below the original lateral. These new ribs can also be tied in to bamboo canes. Any growth that is misplaced, or surplus to requirements, can be pinched back (or cut) to one or two leaves at the base of the shoot. All shoots growing directly towards the wall, or away from it, can be removed.
Diagram 43 Formative pruning of a plum fan.
This process is continued in subsequent years, with the new growth gradually filling in the space in the middle of the tree. Over time, these bamboo canes and main branches will form a fan shape against the wall. In the spring of years 2 and 3, the new ribs can be shortened by removing about one-third of the previous season’s growth. Healthy side shoots, in a place where they are needed to fill in gaps in the framework, can be trained into place. Those that are not required can be regularly pinched back over the season to leave just a few leaves at the base. The growth over a season can be quite vigorous, so it is important to keep on top of cutting back new growth, before it becomes congested. It will usually be necessary to prune several times over a season. It is much better to prune young growth regularly, preferably by pinching it out, than to carry out an annual pruning.
Such instructions can seem daunting and complicated, but there is no need to worry too much about getting it exactly right. The important things to remember are training in the new branches and keeping the remaining growth under control.
Once the fan is established, pruning continues to take place over the period from spring through to late summer (see Diagram 44). The branch leaders can be left alone, unless they are growing beyond the space on the wall. In the spring, misplaced and strong vertical growth should be removed, along with exhausted growth and shoots growing away from or towards the wall. The remaining shoots can be thinned to around 10cm (4") apart (see Diagram 45). As the season develops, pinch back the side shoots as described earlier. Cut back any growth that is shading the ripening fruits.
Diagram 44 Pruning an established plum fan (spring to summer).
Diagram 45 Pruning one branch of an established plum fan.
Once the fan-trained tree is mature, the centre of the tree is likely to become bare, with the productive growth towards the outside of the tree. This effect can be controlled by selecting replacement shoots to be grown on over a season to replace branches that are becoming exhausted. The following spring, the original branch can be removed and the replacement tied in. It is likely that fruits will need thinning once the tree is cropping well.
Pruning plum cordons
Although it is unusual, plums can be successfully grown as cordons where space is limited. They are best grown on Pixy root-stock and can be planted as close as lm (3') apart. To form a cordon, first plant a maiden at an angle of 45 degrees. The laterals that emerge from the trunk should be kept to 15-20cm (6-8") long each season. Side shoots that emerge from them should also be regularly shortened to around 5cm (2") long. This involves regular pinching back over the season to keep the tree compact. When a lateral becomes exhausted, it can be replaced by cutting back to a replacement shoot.
Harvesting plums
It is easy to tell when plums are ready to harvest. Ripe plums will be soft and sweet. Picking a plum from the tree and eating it will tell you whether it is ripe or not! Wasps might also give you an early warning that your plums are ripening. They are likely to start eating your plums just before they are ripe – in severe cases, you might need to harvest your plums a little early and leave them on a sunny window-sill to ripen fully. Wet weather can also spoil fruit, by causing the flesh to split. You may need to harvest earlier than planned if hail or heavy rainfall threatens, so it’s worth paying attention to the weather forecast.
Not all your plums will ripen at once. You will need to harvest each tree several times to pick all the fruits at their best.
At the same time as harvesting, remember to remove any fruits that are suffering from brown rot (see Chapter 9, page 132). This will help to prevent this troublesome disease from reinfecting the tree the following year.
Plums, being a soft fruit, will not keep for any length of time. Once they are at their best, you will need to use them quickly. Of course, you can eat them fresh from the tree – for the finest plums, this is perhaps the best way of enjoying them. It’s a special moment when you bite into a home-grown greengage, enjoying its juicy, honeyed, toffee-apple-like taste.
Cooking plums are different: although they also have a wonderful taste, their tartness makes cooking them almost a necessity, but the result is no less a pleasure. Damsons and bullaces are particularly sharp fruits that require plenty of sweetening.
Cooking
There are, of course, many delightful ways to cook plums. I remember the wonder of ‘Tinker, tailor, soldier, sailor . . .’to the accompaniment of plum crumble and custard as a child. There are also many equally enjoyable, but more sophisticated, dessert recipes that include plums: Alsatian greengage tart, plum torte and plum cobbler are just a few.
There are also savoury uses for plums, often as accompaniments to poultry or game, where the plums’ rich, fruity taste is a perfect contrast to the meat.
Preserves and bottling
Plums are excellent for spicy chutneys and ketchups, while, on the sweeter side, jam and jelly recipes abound. Damson cheese was a traditional use for these fruits in the north of England. Bottling, either in syrup or in alcohol, are other options for preserving plums.
Freezing
There are several ways to freeze plums and damsons, either dry or puréed. There is a tendency for the skins to become tough when frozen; using ascorbic acid or scalding with boiling water will help to avoid this problem. Once the stones have been removed, plums can be frozen, either stewed or puréed.
Drying
Prunes are the dried fruit from particular varieties of plum that have been bred for the purpose, such as La Petite d’Agen from France. School dinners did their best to put a generation of children off prunes, but they are starting to recover their popularity, especially now that their health benefits have been realised.
Dried plums (as opposed to prunes) are now beginning to emerge on to the market. You can dry your own plums at home. If you don’t have a dehydrator or drying box, you can dry them cut into slices in a very low oven (the lowest setting possible – around 60°C [140T]) for 12 to 24 hours. Brushing the plum slices with one part honey and two parts water is said to reduce vitamin loss and discolouration.
Making alcohol
Plums have a long association with alcohol. Even sloes, the bitter relatives of plums, are gathered to make sloe gin. In many eastern and northern parts of Europe, liqueurs are made from plums. Particular varieties of plums are used to make slivovice or slivovitza (the exact name varying from one country to another) – a type of plum brandy. In Britain, plums are more traditionally used to make plum wine.
