Why a heavy crop isn't always good news

There's a particular pleasure in standing under an apple tree in early July and seeing every branch bowed down with tiny green fruitlets. It looks like abundance. In truth, it's often the moment a tree sets itself up for a disappointing autumn. Apples naturally set far more fruit than they can possibly bring to a decent size, and if you leave every one of them on the tree, the tree will simply spread its resources more thinly.

The result is a crop of small, hard, poorly coloured apples, many of which will drop before they ripen anyway. Worse, a laden branch on a dwarf rootstock or a brittle variety such as Bramley can snap clean under the weight of a wet summer crop. Thinning is the single most rewarding job you can do in the fruit garden in midsummer, and it takes less time than you'd think.

Wait for the June drop before you start

Apples shed some of their own accord in early summer, a natural adjustment usually called the June drop. Don't rush in before it finishes, or you'll simply be doing the tree's work for it and then doing it again. In most of the UK the drop tails off in late June, though it can run into early July in a cold, slow season.

Start thinning when the remaining fruitlets are roughly the size of a marble to a golf ball, about 20–25mm across. This is usually mid-July in the south and a fortnight later further north. Fruit thinned at this stage still has plenty of growing time to swell. Leave it until August and you'll have done the work without gaining much of the benefit.

How much to take off, and which ones

The golden rule is one fruit per cluster, and roughly 10–15cm (4–6 inches) between the fruits you keep. On a well-loaded tree that often means removing one fruit in every two or three, which feels brutal the first time you do it. Trust the process.

Work through the clusters in this order:

• Remove damaged fruit first. Look for codling moth entry holes, sawfly scarring, scab lesions, bird pecks and any fruit that is misshapen or yellowing. These will never come to anything and can harbour pests.
• Then take out the smallest fruitlets in each cluster, which are the ones most likely to be shed anyway.
• Then thin for spacing, until you are left with a single healthy fruit roughly every hand's width along the branch.

On varieties that crop in tight bunches, such as Discovery or Katy, you may need to remove whole clusters rather than single fruits. On a light-cropping tree, thin only where fruit is touching, and leave the rest alone.

The king fruit question

You'll notice that in many clusters the central fruitlet, known as the king fruit, is noticeably larger than its neighbours. It grew from the first flower to open, so it had a head start.

Conventional advice used to be to keep the king fruit on the grounds that it's the biggest. In practice, king fruits are often lopsided or flattened, because they set slightly later in development than the side fruits and can be squeezed by them. Many growers now remove the king fruit and keep one well-shaped side fruit instead.

Either approach works. If the king fruit is round and clean, keep it. If it looks lumpy or has a bruise, take it and leave a good side fruit in its place.

Technique, tools and a bit of care

Use your thumb and forefinger to pinch or twist the fruitlet away, leaving the stalk attached to the tree. Don't tug hard enough to strip leaves or knock off the fruit you've just decided to keep, and don't tear at the spur. If a tree is carrying very short-stalked fruit, or the crop is dense and fiddly, small sharp snips or a pair of nail scissors are quicker and gentler than fingers.

A few practical points:

• Work from the top of the tree downwards, so you don't knock fruit off lower branches as you reach.
• Hold a bucket or trug close to the branch rather than letting thinnings fall to the ground, where they can attract wasps.
• Dispose of pest-damaged fruit in the household waste, not the compost heap, to break the codling moth cycle.
• Clean your snips between trees, particularly if you've been working on one with canker.

Give heavy branches some support while you're at it. A stout forked prop, padded where it meets the bark, will save a limb on a windy night.

Afterwards, and the payoff in autumn

Check the tree again in August. A second, lighter pass is often worthwhile, especially if the tree set unevenly or a late flush of fruit has escaped your notice. Keep the tree well watered through dry spells and top up the mulch around the base, but keep it clear of the trunk.

Thinning doesn't just improve this year's fruit. Apples tend to alternate, cropping heavily one year and barely at all the next. By reducing the load now, you help the tree build flowering spurs for next spring, which smooths out that boom-and-bust rhythm. You'll notice the difference in the size, colour and flavour of the apples you pick, and in how well the tree carries its crop without complaint. It's twenty minutes of fiddly work for a September of proper apples.