Thinning 101

Mid spring is the time to start thinking about the “whys”and “hows” of fruit thinning, or manually removing some of the fruit from your trees. A lot of people have heard of it, but most people don’t really understand it – and anyway, pulling fruit off the tree just feels wrong!

One of the least understood reasons for doing this job is to try to break the cycle of biennial bearing that many fruit trees naturally adopt.

Angeleno plums before thinning
Angeleno plums before thinning

Here’s a typical bunch of plums on a tree as they naturally set. As you can see, there’s LOTS of plums in these two bunches at the end of a small branch.

This is what we’d call a “heavy” crop, and maybe enough to tell the tree to take a year off next year, or in other words, have a “light” crop.

Angeleno plums after thinning
Angeleno plums after thinning

If we remove all but two of the plums, we’re sending the tree a signal that it’s having a light crop this year, which will encourage it to have a heavy crop again next year.

But the good news is that if we do this job early enough we’re sacrificing very little actual fruit production, as the tree will put the same amount of energy into the fruit you leave on the tree as it would have to the big bunches of fruit.   

Managing the crop is one of your main jobs as the caretaker of your fruit tree, but there’s several other excellent reasons for thinning as well, including protecting the structure of the tree, getting more usable fruit, and protecting it from pests and diseases.

Of course knowing how much fruit to remove is the tricky bit, and one of the things that stops people doing this job, or doing it properly. We’ve included charts to help you calculate the variables in the Fruit Tree Thinning short course.

Did you get the thinning right?

As we go about picking in the orchard during the apricot season, we see the end result of the thinning we did a couple of months ago – where it worked, and where it didn’t. Here’s a bunch of apricots that were missed in the thinning, and you can clearly see the outcome.

Out of this bunch of four, two apricots have grown normally, and two are stunted, slightly shrivelled, and not really edible – these are the ones that should have been removed when we were doing the thinning.

When they’re removed, you can see that we’re left with two reasonably sized, delicious looking apricots. But…how much bigger could they have been?

The energy that the tree has put into the two discarded fruit would have been better put into growing just two pieces of fruit in the bunch to a larger size.

This is just one reason why it’s a good idea to do thinning early, hard, and thoroughly! We’re aiming to always maximise the ratio of usable, edible fruit to core/stone that the tree produces.

We’ve also seen quite a few of these broken laterals in the orchard, which is another problem caused by leaving too much fruit on a branch that isn’t big enough to carry the weight.

Having put all our care and attention into growing and pruning the tree, it’s then our responsibility to make sure we don’t leave too much fruit on any one branch or lateral than it can carry, to protect these precious growing areas.

Sorry, tree…