I am particularly fond of restricted forms of training for fruiting plants. Not only do they allow one to exploit walls, fences, and glasshouses to their full, they make very attractive dividers and enable more varieties to be grown in a given space. Cordons are particularly easy to grow and can be surprisingly productive. A row of oblique cordons – those grown at an angle, typically 45 degrees – takes up little space and can be readily fitted in to even modest gardens. To be fruitful and remain under control, however, requires careful attention to pruning.
Pruning of restricted forms of apples and pears, such as cordons, espaliers, and stepovers, is largely carried out during the summer. The productivity of such restricted forms depends on the formation of a system of fruiting spurs. Winter pruning encourages vegetative growth, and is therefore largely concerned with the removal of dead or diseased wood and tidying up overcrowded spur systems. To a large extent, vegetative growth is the enemy of productivity. Summer pruning removes much of the new growth, not only keeping the tree within its allotted space but also encouraging fruit buds to develop as opposed to growth buds. The development of fruit buds is a natural survival response to the stress caused by reducing significantly the tree’s food supply. Summer pruning also helps this season’s developing fruit, by removing excessive growth that both takes energy and shades the fruit. Mid to late July is an ideal time to perform such pruning, although I would be guided by the amount of new growth and the state of the developing fruit. This year, pruning of our cordon apples and pears could have begun as early as mid June – this being their second year since planting, they put on a great deal of vigorous new growth, the bottom third or so of which was ripening early.
Summer pruning is actually a fairly simple matter, and one can be guided by just a few general rules. Where the form is established, the leader(s) can be shortened to one bud, otherwise tie in the new growth. New laterals – shoots arising from the main branch, in the case of cordons, or one of the framework of branches in the case of espaliers – are pruned to three leaves or buds past the basal cluster. Sub-laterals – shoots arising from previous laterals – are pruned to one leaf or bud past the basal cluster. The basal cluster is that group of tightly packed leaves that often forms near the junction of the new and old growth. Short laterals, if terminating with a potential fruit bud, may be left unpruned. One can generally distinguish between growth and fruit buds by their shape; growth buds tend to be small and pointed, whilst fruit buds tend to be fat and rounded. Whilst pruning, one should also look out for any suckers from the rootstock; any shoots emerging from below the graft union should be removed entirely.
One should be guided by common sense and experience rather than the exact application of these general rules. However, for anyone new to pruning, they provide a sound starting point. Such pruning may seem harsh – a great proportion of the vegetative growth will be removed. Yet allowing this growth to remain will not result in a productive tree, and in particular its removal is essential to keep restricted forms within the available space. One must be ruthless in the removal of unproductive wood; sometimes, however, where short shoots are concerned, one can postpone the odd tricky decision until winter pruning, when the structure of the spur systems will be more clearly visible.
Having cleared up the excessive growth, one can also take the opportunity to look over the developing fruit that can now be more clearly seen, and remove any that are damaged, diseased, misshapen, or growing in awkward positions. Removal of excessive fruit is also beneficial for addressing biennial bearing; that is, the habit of fruiting heavily only every other year. Biennial bearing is often a trait of particular varieties, although permitting a heavy crop to be carried in one year, will tax the tree and may result in a poor crop in the following year. This habit, whether particular to the variety or encouraged through over cropping, can be tamed by careful thinning of the developing fruit. Such thinning is also beneficial to the size and quality of the remaining fruit, and obviously has the most impact if carried out early in the season. However, one will often consider thinning after the so-called ‘June drop’ when trees naturally tend to shed excess crop. In any event, when summer pruning has been completed it is worth considering any further thinning that may be needed, now that the fruits can be more clearly seen.
Secondary growth may well occur after summer pruning. Such growth can be cut back to one bud later in the year.