New to this site, and to growing apples in general. I am in No. California…
I have a 4-in-1 apple tree that has been in the ground since fall. Two of the grafts are twice as long and thick as the smaller two. They have also, due to a real warm spell, blossomed and leafed out quite a bit. The two smaller, though they have buds, show no signs of even swelling yet. Everything I’ve read warns not to let the larger grafts dominate the others. When is the right time to prune them back and how far?
Thanks in advance,
the right time was a few weeks ago when everything was still dormant. I would be afraid to prune now. Pruning stimulates growth and these are already strong growers. what you can do is Ring the tree. You cut out a U shaped piece of bark mid-spring and that will reduce the vigor of the limb.
You can also do bark inversion on the main trunk and you’ll have reduce vigor but the tree remains productive and produce high quality fruits. You do this once every 4 years.
Keep summer pruning the larger limbs to bring them to the size of the other two. You can do it in one season or over two seasons. You’ll lose some fruiting spurs but that is the price to pay for a multi graft tree.
Establishing balance can be important with new limbs and more so if they are different varieties. One or two can easily take over in that stage. Ideally, you want branches space on the trunk, 8 inches or more for full sized trees, and of similar hieght and diameter. That’s just an ideal. If there is a central leader of any kind, you probably want it partially checked in growth by substantial lower limbs. It has a lot to do with which branches are tallest. Taller shoots will often create a viscious cycle by outgrowing the shorter limbs, supressing them and gaining dominance, when that is exactly what you don’t want. You can use a few methods to deal with that. One, shorten the long ones to the length of the short ones, or even shorter if they seem extra vigorous. If you want the tree to grow out, prune to outside facing buds. If you want it to grow up, prune to inside facing buds. The angle of the branches is also important. Very upright shoots will usually grow faster and taller. So look to keeping similar branch angles with spreading, tying and cutting to appropriately bud directions when shortening. Also, if some limbs seem especially weak, notch above them through the bark, about 1/3 around the tree trunk. You can use a rat tail file or knife. Make sure you take off a thin layer of wood or scrape exposed wood to remove the active cambium. Notching can really help guide resources into a weak branch. Notching below buds and branches is supposed to have the opposite effect, but I don’t have a lot of experience with that technique. I’ve ringed and cut large notches out of strong branches to curb growth as lordkiwi suggests, but with limited observable effect so far. Not to say it doesn’t work, but for very vigorous established branches, it hasn’t appeared to have a lot of effect. I second bleedingdirt’s suggestion to summer prune up until late summer to check growth in over vigorous shoots, but I would start now by making them equal, or the over vigorous ones slightly shorter and notch above the weakest. Commercial orchardists can’t afford to micromanage, but we can cut, spread, bend, stake, snip, pinch and disbud from now through early fall to make trees take desired forms.