Apples and pears are ideal candidates for cordon training. Oblique cordons were commonly planted along the walls of the traditional walled kitchen garden. Stone fruits, including plums, are more likely to be grown as fans. There exists, amongst some contemporary authors, the notion that stone fruits are not suited for cordon training and will bear poorly if so grown. However, I am not at all convinced about this, and, at least in the case of plums, am fairly sure that one can grow these quite successfully as cordons.
Cordons are the most restricted form of training, constraining growth to, most often, a single stem. Pruning is quite harsh, and aims to develop systems of fruiting spurs along the length of the stem. Apple and pear cordons were traditionally planted at an angle, typically of 45 degrees, which allows a longer stem for a given height, and, critically, helps to contain the vigour of the tree and promote good bud break along the entire length of the stem. Vertical cordons are entirely possible, but tend to produce their growth towards the top of the tree. Vertical forms are often developed if multiple stems are trained, such as in the ‘U’ cordon. Lowering a branch from the vertical promotes the development of fruit buds, which is exploited in other forms, such as the festoon. In our first garden, we had a Victoria plum which I festooned by tying down the young whippy branches so that they arched back down towards the ground. Fruit bearing on these branches can be quite remarkable. In fact, they often need thinning, and we had to provide supports so that the branches would not break under the weight of the fruit.
For plums, there are some possible drawbacks with cordon training. Most important, perhaps, is that stone fruits are, in general, more prone to disease than apples and pears. Diseases such as silver leaf can infect via pruning cuts and other wounds, so the harsh pruning regime needed to manage the vegetative growth might carry additional risks. In the UK it is normal to avoid pruning stone fruit from late autumn to spring to minimise the chance of infection, as this is when the most fungal spores are produced. Another important concern is whether plums will form suitable fruiting spurs under cordon pruning and bear a useful crop. I have seen it suggested that they do not readily produce such spurs, however, we have observed with our own trees that these spur systems can be developed quite easily.
Some years ago, my dad planted a Victoria plum tree in his back garden. As other planting encroached on the space, he was forced to dig it up and planted it, temporarily, in a large pot. At this point we thought it might be fun to try a little experiment and trained this as a double cordon, comprising two vertical stems. After a year or two it was moved to a spot by the fence of our kitchen garden. To begin with it did not achieve much. However, we manured it and pruned it to encourage fruit buds to develop and this year it appears to be laden with fruit buds on reasonably compact spur systems. Provided buds are not molested by winged nuisances and the blossom escapes any damage from late frost, I am fairly sure we will be seeing a great crop of plums from what is a very small footprint.
We have six plums and gages being fan trained against the west fence of the kitchen garden. Three have yet to establish themselves, as they were only planted last winter. Three from the previous year, though, have developed their main ‘Y’ branches as well as a good number of side shoots that will form part of the main framework. Interestingly, though, one variety – Reine Claude Violette, also known as Purple Gage – has been most reluctant to form side shoots of any great length, instead developing many short spurs that appear to be heavily laden with fruit buds. Whilst the other varieties have produced some spurs, it seems entirely likely that some varieties would be better suited than others to cordon training. I suspect that Reine Claude Violette would make a very good cordon.
Fruit buds developing on Victoria:
Fruit buds developing on Reine Claude Violette:
It is a little odd that this general perception that stone fruits are not suited to cordon training has arisen when there are now many dwarf cordons, known by various terms such as columnar fruit trees or minarettes. These seem to be nothing more than vertical cordons on, typically, rather dwarfing stocks. I am not, however, fond of these, preferring a more vigorous rootstock than they usually seem to be grown on. Plants can be kept under control by means other than a weak rootstock, and I am not convinced that a rootstock that results in the minimal vegetative growth that these sorts seem to put on is somehow still capable of bearing a decent crop. Perhaps I am wrong in that, but I have yet to see an impressive tree grown on an especially dwarfing stock. It is not even a case of just bearing a crop; it is about bringing the fruit to perfection. Even with a vigorous rootstock, a heavy crop may need thinning to produce good quality fruits.
It is interesting to note that, in times past, cordon training was recommended for many fruits. In Cordon Training of Fruit Trees by Rev. T. Collings Brehaut, 1860, cordon training is recommended for pear, plum, cherry, apricot, and even peach trees. The latter, requiring some form of replacement pruning to provide a supply of one year old fruiting wood, are given special treatment. Detailed instructions are provided as to the pruning regime that will, according to the author, result in the development of fruiting spurs. He is not alone, either; cordon training of plums is referred to in numerous publications from the latter half of the 19th century. Samuel Wood in The Forcing Garden, 1881, discusses growing cordon trained plums under some protection during the spring in order to protect the blossom and in The Science and Practice of Grafting, Pruning, and Training Fruit Trees, 1862, M. Du Breuil notes that single oblique and vertical cordons are “a particularly suitable form for the plum”.
With the great advantage of being able to fit a number of different varieties in a small space, even though it might not be recommended, I would think it well worth trying to grow plums as cordons. If one purchases a couple of bare root maiden whips from one of the specialist fruit nurseries, it is not a particularly expensive experiment. I am not sure whether I could fit in any more trees, but I would certainly like to try another cordon plum somewhere, just to see how well it performs. We have a number of cherry trees being fan trained in the fruit cage. I do wonder, though, whether a cherry grown as a cordon would bear a useful crop. I suspect this may be more marginal than with plums, but it might be an interesting experiment if I can find a space. It seems to conflict with more recent opinions that I have read, but Brehaut certainly suggests that they can be successful, as does Samuel Wood, who has this to say of the cherry:
The Cherry is especially adapted for the ‘cordon’, more so than any other class of fruit tree; for when the treble cordon (which I consider the best form for wall Cherries) is planted two feet apart, and trained ‘oblique’ against the sun, it may be maintained perpetually for years with much less trouble than in the case of any other fruit tree.