My 89 year old Dutch teacher is his full life busy with espalier fruit trees. He have so mutch knowledge how to manipulate the growth of fruit trees.
For espalier fruit trees I got there are a few very important rules:
a) Growth rules of Vöchting and Koopmann.
b) First establish the lower or outer branches (depending on type of espalier shape) before u start the next layer. If not, these branches will always be weak and give less fruit.
c) Pruning in winter gives extra growth.
d) Pruning in summer can produce fruit buds.
e) 1 kg fruit reduces 1 meter of growth.
f) By bending horizontal the growth reduce.
g) By bending vertical growth increase.
h) Buds in upwards direction grow fast (mostly we don’t want this).
i) Buds in horizontal or downwards direction grow slow.
j) Growth can be reduced by root pruning.
k) Growth can be reduced by sawing a cut of 1/3 deep in the branch (sometimes 2 on each side but at 20 cm height difference). Do this when buds just wake up.
l) Rootstock and quality of ground influence growth and size of the tree.
m) By notching u can wake up buds. Do this when buds just wake up.
n) Length cuts through the bark give extra thickness and growth. Do this when buds just wake up. Use this for example when main branches are not symmetric in thickness.
o) Fruit buds are produced because of slow growth.
p) 1 fruit needs 20 leaves to get the perfect tasted and aroma (pear and apple).
q) Apple have to be in full ‘wind’. In front of a fence/wall it’s too hot and less air circulation, what can give extra deceases.
r) Pear can grow in front of a fence/wall. Some varieties are better for full sun and other for more shade.
Waterspouds grow vertical and strong on top of branches. They have to be removed in may by pinching at 2 a 3 leaves. Pinch these the full summer. If there are still left, prune them in winter fully to the branch. Don’t leave a stomp and side buds.
So to get back to your problem. You’re apple trees are trained in a horizontal espalier shape. They do not produce fruit buds.
Probably u prune to shot and because of this u wake up new growth bud no fruitbuds. Every time u prune there will be 2 ore more new branches and u again u prune them to short hence u get more short branches. U get a big wood cluster with small branches but not fruit.
Fruit buds on apple exist on “vruchtzetels” fruitclusters:
A established vruchtzetel exist on the main branch and is in winter 15cm long with several types of fruitbuds and fruit wood. The last bud of the vruchtzetel is a normal bud that produces new growth in summer (1)
The fruitwood can exist from long fruitwood with at the end a fruitbud (2), short fruitwood with at the end a fruitbud (3) or flowerbuds (4).
At the end of summer the young branch (1) will be between 50 to 70 cm. The young branch is feeding the fruit with sugars.
The goal of a vruchtzetel is to produce quality fruit at the first 15 cm of the main branch.
Vruchtzetels are produced as follow:
- In june there will be new growth from the main branch. All new growth in 45° angle or lower can be converted to vruchtzetels. There can be 8 to 10 vruchtzetels per meter branch. All other growth will be pruned back to a stomp of 0,5cm (kroonsnede).
In the week after 21 of June the growth of the tree will stop or slow down for a week. This is the moment to start producing fruitbuds.
- All new growth that will be converted to a Vruchtzetel (fruitbranch) is pinched at 6 to 10 buds (depending on the varieties fruit tree).
(a pear that produce short fruitwood will be pinched at 6 buds (like conference), a pear that will produce fruit on middle long fruitwood will be pinched at 8 buds (like Doyenne de Comice) and a apple will be pinched at 9 to 10 buds.)
The last bud have to be in the downwards direction. If not remove the last bud and pinch to a further bud what have downwards direction.
- From the last two buds new growth will start to grow.
- 6 weeks later remove the upper new growth completely. The lower new growth at the end pinch to 2 leaves.
- In winter there will be 6 to 10 buds at the vruchtzetel and at the end there wille be some Young branch without fruitbuds (nr 1 in the picture). Mostly its longer as 35cm.
Prune the first young branch (nr 1 in the picture) of the vruchtzetel (it’s the one we pinched to 2 leaves last summer) to one bud in the downwards direction. (if not, remove a bud and prune further to a downward bud).
- The next summer there will grow fruitwood at the beginning (the 6 to 8 buds) of the Vruchtzetel. (short wood with thick buds)
- Pinch in June like last year.
- The next winter prune to a bud just behind the fruitbud. Now you create a Vruchtzetel with fruitwood.
- Every year make shure only the last bud of a vruchtzetel is a normal bud with new growth. Only prune this new growth in winter. These leaves will feed the fruit with sugars and make the fruitbuds will not be converted to normal branches.
If the new growth in winter is longer as 70cm there can be made space for more fruitbuds at the Vruchtzetel. If the new growth is smaller as 50cm there have to be fruitbuds skiped.
If this all will not work there is also a different method to create fruitwood. It’s called Lorette snoei. This can only be used by specific varieties and there have to be a very strong growth.