A plum job for summer

Saturday 14 July 2012

The combination of low temperatures in April and the absence of pollinators has made for a poor plum harvest.

Custom byline text:

Dave Allan

Still, every cloud has a silver lining and this month is a good time to get your tree in good shape for an excellent crop next year.

Although pruning stresses all plants, plums are especially susceptible, which is why only light, not severe pruning is usually best. The well-known 18th-century Scottish gardener, James Justice, made this point in 1754: "And our Gardeners, or such as pretend to be so, cannot give them [plums] too much Discipline with a Knife, the Wood being strong and hardy and the Fruit easily obtained. But they are quite mistaken; few Fruit trees can endure the Knife worse."

Justice, unlike some later writers, realised plums should be pruned in summer, not late winter, recognising that plums healed more slowly than many other plants. But he didn't know that summer pruning allows wounds to heal properly, protecting plums against the deadly silver leaf disease. During late autumn and winter, the fungal spores of silver leaf enter the tree through unhealed wounds. In early spring, the spores exude toxins which are carried up through the tree by sap. These toxins separate leaf tissues, and the resulting air spaces make the leaves look silvery. Meanwhile, the fungus kills branches, causing dark staining in the wood.Plum wounds take a month to heal, so prune over the next two or three weeks and take away all the prunings. You can easily compost this year's green, sappy shoots. If you don't have a shredder, use a rotary mower. Simply pile up the green material on the grass and carefully lower the machine on to the heap. Collect the shredded branches in the grass box and they are ready for composting.Keeping plum pruning to a minimum means you often end up with tangly growth and branches setting off in the wrong direction. This is a good year to give trees an overhaul because of the aforementioned late frosts, which destroyed any plans for a bountiful crop of plums, including mine. Even my Early Transparent Gage, fan-trained against a snug, south-facing house wall, will bear no fruit, never mind the tough Victoria and Marjorie's Seedlings in the orchard. There's therefore no risk of dislodging fruit while removing larger branches. This year, the trees will put more energy into growth rather than fruit, so reduce next year's congested branches by thinning out now.Plums are usually fan-trained or grown as bushes. However you grow them, prune them to allow good air circulation, thus preventing many fungal problems, and to let the sun reach and ripen all the fruit.The fan shape does this superbly. A fan-trained plum also makes full use of vertical wall space, so is ideal for smaller gardens. Plum varieties that have been grafted on to a dwarfing rootstock, such as Pixy or St Julien A, are especially good candidates if your space is limited. Grow two branches, to left and right of the centre, to form the base of your fan. Train the stems from these branches into the shape of a fan and encourage them to grow sideways, never vertically. Earlier spring pruning entails thinning buds growing from the main stems by removing them with your fingers. The remaining buds should be no closer than 10cm, with all vertical and outward-facing buds removed.If you didn't get rid of unwanted new growth at this early stage, prune to the desired shape now. Next year's fruit buds will form along mature wood and at the basal joins of new shoots, so remove tangled growth to prepare for next year. You can prune hard, confident in the knowledge you're not denying yourself any plums. A forward-leaning branch can be neatly sawn back to its join the main stem. Vertically-growing stems and those too high to reach are also for the chop. You'll end up with a much neater and more accessible tree.You can also give bush-trained plum trees a thorough pruning without losing any harvest. Essentially, as with all fruit bushes, you ensure good air circulation by keeping the centre of the tree open. Allow only four main branches, spread round an open centre, to form the tree's skeleton. Make sure you leave yourself space to get in to the centre of the tree. The stems growing from these branches should be encouraged to grow horizontally or diagonally. Vertical stems soon become impossible to harvest.You will get a much better crop by reducing the number of fruiting stems. An uncontrolled mass of throttling growth produces small, weak, damaged fruit, so thin out the branches by removing crossing and vertical twigs and stems. Thin, thin, thin. The plum tree branch that collapses under the weight of its own fruit is well known, but is easily prevented by sensible pruning now. n

Contextual targeting label:

Weather

Commenting & Moderation

We moderate all comments on HeraldScotland on either a pre-moderated or post-moderated basis. If you're a relatively new user then your comments will be reviewed before publication and if we know you well then your comments will be subject to moderation only if other users or the moderators believe you've broken the rules, which are available here.

Moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours. Please be patient if your posts are not approved instantly.

A plum job for summer

Commenting & Moderation

MOST READ

SPONSORED LINKS

MOST COMMENTED