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.


Insects in fruit trees

In spring we reckon it’s a good idea to visit your fruit trees at least once a week, and have a really good look at the leaves, flowers, fruit and bark. It’s a good way to keep track of the health of your tree, and stay ahead of any disease issues that show up.

One of the more interesting looking insects you might see on your fruit tree
One of the more interesting looking insects you might see on your fruit tree

While you’re there, try to spot any critters living in and around the tree, like this great bug we found on an apricot tree.

It doesn’t matter if you can identify the bug or not (though that can sometimes be useful) – it’s safe to assume that it’s playing an important role in the ecosystem (like pollination, pest control, or acting as a food source for someone else), even if we don’t know what that is.

A bee working hard on a peach flower
A bee working hard on a peach flower

Many people mistakenly think pollination depends solely on bees, whereas in fact many insects play an important role (you can find out more about this important topic in Bees and Pollination).

Though it’s absolutely fascinating trying to figure out what sort of bugs you’ve got, identification is much less important than the fact that you have lots of biodiversity in your garden or on your farm. In short, the more different types of bugs you can count, the healthier your system is.

Amazing antennae...
Amazing antennae…

Why is biodiversity so important?

We often get questions from people who have noticed bugs or insects on their fruit or trees, and are wondering if they should get rid of them, and if so how?

That’s not our approach at all!

In a healthy, biodiverse system there should be literally thousands of different types of insects around, and they all play a part in an incredibly complex system that (if it’s not interfered with) will generally keep itself in balance.

Unless you’re an insect specialist, there’s little chance that you can identify them all or even understand whether they’re a “pest” or a “predator” – in fact, many are both. For example earwigs are a dratted nuisance in apricot and cherry trees, but a useful predator eating up millions of aphids in apple trees.

An earwig on a leaf  - pest or predator (or both)?
An earwig on a leaf – pest or predator (or both)?

So we take a different approach.

Rather than focusing on the insects themselves, we focus on protecting our fruit and our fruit trees from damage.

The methodology we use, both on the farm and in our ebook What’s Bugging My Fruit? is not to try getting rid of the bugs (which is usually impossible, frustrating and expensive), but to understand their life cycle and look for vulnerabilities where we can often use small, easy, physical interventions to stop them doing damage to our precious fruit. Over many years of growing fruit organically we’ve found this method much more effective.

So when you’re doing your weekly inspections of your fruit trees, look for bugs, but also look for damage on the fruit and the trees, because that’s what will guide you as to the appropriate prevention techniques.

A spined predatory shield bug
A spined predatory shield bug

Hello peaches…

Anzac peaches need thinning
Anzac peaches need thinning

The Anzac peaches (one of the first to flower at our place) have set a good crop as usual, and it’s time to start thinning.

This is a good time of year to start assessing the impact of a couple of common diseases that can play havoc with our fruit trees, often without our realising it. 

You’ll also be thinning your apricots soon (if you haven’t already started), so while you’re doing so, it’s a good time to be looking our for signs of blossom blight in your tree.

Castlebrite apricot tree with blossom blight
Castlebrite apricot tree with blossom blight

Even though this disease does most damage when the tree is flowering, it can also affect the fruit that has set – because the disease that causes blossom blight also causes brown rot.

It’s not unusual to see remnants of it alongside healthy apricots, if you’ve had a mild case.

Flowers infected with blossom blight
Flowers infected with blossom blight

If you notice any of these diseased flowers on your apricot tree and you also have healthy fruit, it’s a good idea to knock or prune any diseased flowers and shoots off, for two reasons.

The first is that they can contribute to disease outbreaks next year, but the more urgent reason is that the pathogen that causes blossom blight also causes brown rot later in the season, and developing fruit is very vulnerable, as you can see in the following photo:

Photo showing Brown rot infection of a young apricot (blue arrow) that started from a flower that died due to Blossom blight infection (red arrow)
Photo showing Brown rot infection of a young apricot (blue arrow) that started from a flower that died due to Blossom blight infection (red arrow)

The other disease to check for is leaf curl, which is usually fairly obvious, the red leaves are a dead giveaway.

Leaf curl on a peach tree
Leaf curl on a peach tree

Only peaches and nectarines are affected by this tree, and if you’ve had a really bad case, it can also affect the fruit, so this is another thing to be looking out for while you’re thinning because you may as well pull the infected fruit off.

Affected fruit looks like this:

Leaf curl infection on a Goldmine nectarine
Leaf curl infection on a Goldmine nectarine

It’s not uncommon to end up with one of these infections despite having sprayed, which is super annoying.

There’s a couple of potential reasons for this. The first is that you may not have the right spray equipment for the size of the job you need to do – you can review the various options in this short course (because if you’ve gone to the trouble and effort of spraying, it would be really good to make sure it’s going to work!)

The second reason is that you may not have got the timing quite right, and the right conditions were in place for the fungal disease to take hold in the tree unimpeded.

Of course the long term aim is to get our orchard and trees healthy enough so they don’t need spraying, but while we’re building this biodiverse paradise, a bit of crop protection can go a long way!