Why are my apples so small?

Four causes account for nearly every case of small fruit — too many of them, too little water, too little light, and an old congested spur system — and all four are fixable.

Difficulty: beginner
Time: 30 min
Read: 4 min

Short answer

Overcropping is the usual answer: a tree carrying twice what it can fill produces half-size fruit. Thin to one fruit every 10–15cm after the June drop, water through July and August when the fruit is swelling, prune to let light into the centre, and cut out old congested spurs in winter.

Fruit size is set by how much sugar and water each individual apple receives, which depends on the number of leaves working for it, the water available while it swells, and how much competition it has. Variety sets a ceiling — a Pixie or an Egremont Russet is never going to be a Bramley — but within that ceiling, small fruit is almost always the tree spreading a finite amount of resource across too many apples.

Step by step

Count the crop before blaming anything else.If the branches carry clusters of four or five fruits touching each other, the tree is overcropping and that is your answer. Thin next year, hard, after the June drop.
Think back to July and August.That is when apples swell. A dry spell then, particularly on a dwarfing rootstock or in a pot or in grass, caps fruit size no matter what else is right. A good soak weekly beats a daily sprinkle.
Look at how much light the fruit gets.Apples in the shaded interior of a congested tree stay small, pale and flavourless. Winter pruning that opens the centre improves size and colour across the whole tree.
Examine the spur systems.On an older tree, spurs branch and re-branch into congested clusters carrying dozens of weak fruit buds. Cutting out a proportion of the oldest spur clusters in winter concentrates the crop into fewer, better fruits.
Check the grass and the competition.A tree in mown grass with turf right up to the trunk is competing for water and nitrogen in exactly the zone it feeds in. Clear and mulch a metre-wide circle.
Check the feeding, in both directions.No feeding at all on a poor soil gives small fruit and small pale leaves. Too much nitrogen gives huge leaves, lots of shoot growth and mediocre fruit. Sulphate of potash in late winter is what fruit size wants.
Consider the age of the tree.Very young trees produce smaller fruit for the first year or two of cropping, and very old neglected trees produce small fruit until they are restored. Both are normal.
Check the variety.Some apples are naturally small. Pixie, Egremont Russet, Sunset and most crab apples will never be large. If they are the size the catalogue says, nothing is wrong.

Tips

Thinning is much more effective for fruit size than feeding is. Halving the crop roughly doubles the size of what is left.
Trees in pots or on M27 and M9 need watering in any dry spell from June to September, and inconsistent watering also causes splitting.
Small fruit combined with pale, yellowing older leaves points at a genuine nutrient shortage rather than overcropping.
Mulching in spring is worth more than watering in August, because it stops the water being lost in the first place.

Common mistakes

Feeding a heavily overcropping tree to make the fruit bigger — The limit is the number of apples, not the fertiliser. Feeding a tree carrying twice too much fruit gives you the same number of slightly greener small apples.
Watering little and often in a dry summer — It wets the top few centimetres and encourages surface rooting. One or two deep soaks a week reach the roots that matter.
Leaving old spur systems untouched for years — A congested spur cluster carries many weak buds sharing one branch's supply. Thinning the spurs is a normal part of winter pruning on a mature tree.

If it doesn't work

Heavy crop of uniformly small apples

Cause: Overcropping — Fix: Thin to one fruit every 10–15cm after the June drop, and thin old spur clusters in winter.

Small fruit and some of it shrivelled or dropped in August

Cause: Drought while swelling — Fix: Deep soak weekly in dry spells, mulch in spring, and clear grass from a metre-wide circle.

Small pale fruit only from the middle of the tree

Cause: Shade in a congested crown — Fix: Winter prune to open the centre; remove crossing branches and some upright growth.

Small fruit, small pale leaves, weak growth

Cause: Genuine underfeeding or an exhausted container — Fix: Feed with a balanced fertiliser in early spring plus potash, mulch, and repot if in a container.

Small fruit and enormous leafy growth

Cause: Excess nitrogen — Fix: Stop nitrogen feeds and lawn feed near the tree, use sulphate of potash only, and prune lightly.

Questions people ask

Will thinning really make the apples bigger?

Yes, markedly. It is the single most effective thing you can do for fruit size, and it also protects next year's crop by letting the tree form fruit buds.

Do I need to water an established apple tree?

In an average summer, no. In a dry July and August, a young tree, a dwarf tree, a tree in grass or anything in a pot benefits substantially — that is exactly when fruit is swelling.

Why are the apples at the top of the tree bigger?

More light and less competition. It is a good indication that the crown needs opening up so the same conditions reach the lower branches.