The basic principle of centre leader training is to produce a tree with a good height, and also maximum light penetration to the laterals which bear the fruit. Lower branches need to be longer in order to catch the sun during the late Summer ripening period. The further up the tree we go, the shorter the branches need to be for light penetration, resulting in a pyramidical shape of evenly spaced fruit bearing laterals. The eventual height of the tree is less important with cider apple trees than culinary and dessert varieties since they do not need to be hand picked from the tree.
Some cider apple varieties are easy to train this way, having a natural tendency to produce a strong central stem with plenty of evenly spaced laterals. Others varieties will fight you all the way, regularly losing vigour in the leader, or producing several equally vigorous leaders which will compromise the upward growth we desire. Our attempts at training our trees as centre leaders have generally been successful, but there have been a few problems.
To encourage a young tree to produce a strong central leader with good lateral growth, we tip back (prune) the leader in the Winter to a good bud, by up to two thirds of the previous year's growth, and rub out the two buds below. This should reduce competition for the topmost bud's growth, and also encourage the buds further down to break and form laterals. Sometimes the buds which have been rubbed out are precocious and need rubbing out again in the Spring. On a couple of occasions the topmost bud has failed to break, resulting in no growth until the fourth bud. There have also been occasions when the fourth bud has produced growth so vigorous as to compete with the topmost bud as a leader.
All very interesting, and it just goes to show that you can read all the books on fruit tree training, but there's no substitute for experience. We have had to do a little remedial Spring pruning to correct some of these problems, and some will have to be left until the Winter for similar treatment. Of course sometimes you just have to accept that a particular tree just doesn't want to grow how you want it to and let it go it's own way.
The first pic shows successful growth on one of this year's Tremlett's Bitter trees, a strong leader with lateral growth at the fourth bud (and below). The second pic shows strong competing growth from the fourth bud, which will have to be dealt with during Winter pruning, dependant on which is the stronger.