There are a number of reasons why cordon fruit trees are an attractive proposition. They take up far less space than any other fruit tree form and so allow you to grow a much larger range of varieties in a restricted space. They are easy to keep in shape, and they allow for easy protection, maintenance and picking. They are also attractive, they clothe a wall or fence very well and because they pick up radiated warmth from walls and fences growing cordon fruit trees is often the most satisfactory way of having an orchard in an otherwise inclement area.
This is intended to be a reasonably full guide to growing cordon fruit trees.
These are trees that grown on intermediate rootstocks (so they are not too vigorous) as a single stem. An old cordon looks like a good-sized trunk with no significant branches, but masses of stubby little side shoots. Because there are no major branches, cordon fruit trees cannot crop as heavily as other fruit tree forms, but they are still capable of carrying up to 10kgs of fruit per tree. Grown at an angle of 45 degrees the trunk is longer while still remaining within picking height and so the crop can be increased. Not all fruit are suitable for cordon training, but as a general rule if it has pips it will make a good cordon , while if it has stones it will not. A well-grown cordon apple tree will carry heavy crops while a cherry of the same size will barely yield a punnet.
Against something. Always. Cordons need to be permanently supported with straining wires. Walls and fences make good homes for cordon fruit trees. Walls in particular are warm, although fences radiate heat as well, so fruit trees grown against either tend to fruit earlier and more heavily than their free standing equivalents. If you are going to grow fruit this way be sure to make supporting wires permanent - they are probably going to be there for the next 30-40 years, so use strong wire (ideally fencing wire) and good quality fixings - they will be worth the extra money.
Something seen less often is the practice of growing cordon fruit trees as an internal divider in a garden, in place of a hedge. Grown this way, they make most effective barriers around areas of the garden you may wish to keep separate. Obvious candidates are vegetable patches and swimming pools, but you can grow cordon fruit trees in this way almost anywhere. How nice to eat an apple while taking a breaking from hoeing rows of French beans... and a "cordon fence" is pretty much impenetrable - no more grandchildren falling into the pool.
To do this you obviously need to erect a purpose built structure of posts on which you can fix your straining wires. Use stout timber - we would recommend 10cm square posts, either bedded in concrete or sunk at least 60cms in the ground and braced. A row of cordon fruit trees is heavy and can offer considerable windage if there is a gale.
Apples and pears are the most popular choice for growing as cordons. Choose spur fruiting varieties which suit cordon training and pruning - tip fruiters (almost by definition) will not crop as cordons. Assuming you are growing a number of varieties, which is part of the charm of cordon fruit, do not worry too much about pollination issues. Generally speaking there are enough compatible pollinators present in a range of four or five apples or pears to keep everyone happy.
So go for your favourite varieties but don't forget a good cooker and a pear that you can eat on Christmas Day (Doyenne du Comice would be a good choice here).
There are four things you need to remember about planting cordon fruit trees that do not apply to ANY other fruit.
Otherwise, planting cordons is pretty much the same as planting any other fruit tree. Unless the ground is true clay and does not drain, prepare it by digging it over and removing perennial weed roots, large stones and debris. For every tree add at least one full bucket (two is better) of well rotted compost, horse manure or other organic matter and a small handful of bonemeal. Mix these in well with the existing soil, breaking up any clods as you go.
Now firmly tie long bamboo canes (2.4 metres are ideal) to the straining wires at 45 degree angles to the ground so that their bases are where you want your cordons planted, between 60 and 80 centimetres apart. You will use these canes to train your cordons, and they make good guides to ensure your trees are evenly spaced when planted. Next plant your cordons so that:
Tie the main trunk to the bamboo cane, firm the soil around the roots, and water well. Remember that all newly planted trees need to be watered well in the spring following planting if there is even a hint of a dry spell.
Generally care of cordons is the same as for free standing fruit trees - if you see a pest, disease or wound you deal with it in the same way irrespective of tree shape.
The big difference comes with pruning. With a "conventional" fruit tree, pruning is all about building a shape that will crop to the maximum. The objective is the same with cordons, but in addition you are trying to (mildly) stunt their growth. The logic is pretty simple; all trees will grow as much as they can, but never at the expense of flowering and fruiting. In nature procreation is all.... Therefore, you prune your cordons to deprive them of the food reserves necessary to both grow fast and flower/fruit. As autumn approaches and leaves begin to fall, tree sap falls and is stored in the root system. In Spring, those reserves of sap are used to "jump start" growth. Cordons are pruned in August or early September (often when fruit is still on the tree). All excess wood is removed before its sap has fallen so depriving the tree of some of its winter reserves. In the spring it therefore concentrates on building flower buds which, on a cordon, is exactly what you want.