In favourable conditions fruit trees set more fruit than is ideal. Fruit thinning involves removing excess fruit to improve fruit size and quality. It is carried out on apples, pears, plums, peaches and nectarines.
Many healthy fruit trees drop fruit naturally in early summer in what is known as the 'June drop'. Where a heavy crop has set, too many fruitlets may remain on the branches, resulting in a final crop of disappointingly small fruits. Deliberate thinning of the fruitlets produces better-sized, ripe and healthy fruits, albeit in smaller numbers.
Fruit thinning may be necessary on a range of tree fruit including apples, pears, plums, peaches and nectarines for the following reasons:
- The main purpose of thinning is to improve fruit size and quality
- When a tree is carrying a very heavy crop, the fruits are often small and of poor quality
- Thinning allows sunlight and air to penetrate the branches, so improving evenness of ripening
- There is a risk of branches breaking if trees overcrop
- Thinning lessens the demand on the tree’s resources so it is able to make good growth and develop fruit buds for the following year so avoiding the risk of biennial bearing
- Young trees allowed to crop too heavily will be set back
- Fruit thinning may reduce the spread of pests and diseases, such as brown rot
When to thin fruit
Experienced growers tend to thin in early summer, as this results in the greatest increase in size of those fruits remaining. But for inexperienced gardener, it is best to wait until after the June drop, other than removing malformed fruit. Finish thinning by mid-July.
How to thin fruit
Apples: Cooking apples are thinned harder than dessert apples to obtain larger fruits; aim for one fruit every 15-23cm (6-9in). Dessert apples can be thinned less severely, with one or two fruits every 10-15cm (4-6in). Leave just one fruit per cluster. Thinning can be done using secateurs, long scisssors or with a firm tug between thumb and forefinger. Remove misshapened, blemished fruit or poorly positioned fruit and the ‘king’ fruit at the centre of the cluster which is sometimes abnormally shaped. Aim to leave the strongest and best shaped.
Pears: Can be prone to over-bearing but usually need less thinning; thin clusters to two fruits (one for a small cordon), 10-15 cm (4-6in) apart.
Peaches and nectarines: Thin peaches to one every 10cm (4in) when the size of a hazelnut, then again to one every 20-25cm (8-10in) when the size of a walnut. Thin nectarines to 15cm (6in) at walnut size.
Apricots: Are less prone to over-bearing; thin only if the crop is excessively heavy, to 5-8cm (2-3in) apart when hazelnut sized.
Plums: Are particularly prone to overcropping, so thinning is vital. Heavily laden branches may need additional support with stakes and/or ties even after thinning to prevent them breaking. Use thumb and forefinger to remove fruit to leave one fruit every 5-8cm (2-3in), or a pair of fruits every 15cm (6in).