Why Are My Plums Falling Off the Tree Early?

Watching plums drop before they ripen is demoralising, especially after a tree that looked promising in flower. Early fruit drop in plums happens for several different reasons — some entirely normal, others indicating a problem that needs addressing. Understanding which type of drop you are seeing is the first step to protecting your harvest.

June drop — natural thinning by the tree

All plum trees shed a proportion of their fruitlets naturally in early summer, typically in June. This is the tree's own thinning mechanism — it sheds fruit it cannot support to concentrate resources on the remainder. A moderate June drop is completely normal and beneficial. The dropped fruitlets are small, hard and undeveloped. If the drop is very heavy, leaving few fruits on the tree, it usually indicates a pollination problem or a cold spell at flowering time rather than a fault in the tree's health.

Drought stress causing fruitlet abortion

Plum trees that experience drought during the rapid fruit swell period in June and July will shed fruitlets as a water-conservation response. The drop is often sudden after a dry spell and the fallen fruit is partially developed but not ripe. Water the root zone thoroughly during dry spells — ideally 20 litres per tree per week in drought — and apply a thick mulch of compost or bark chips around the base to retain soil moisture. Avoid wetting the trunk directly.

Plum moth larvae causing premature ripening and drop

Plum moth (Grapholita funebrana) lays eggs on developing fruitlets. The larvae burrow in and feed at the stone, causing the fruit to ripen prematurely and drop early — often in July and August. Dropped fruits from plum moth infestation contain a pink-white caterpillar at the centre when cut open. Pheromone traps hung in the tree in May monitor adult moth flight and help time insecticide applications if needed. Removing and destroying fallen infested fruits reduces the population overwintering in soil.

Brown rot spreading from fruit to fruit

Brown rot (Monilinia laxa) infects plums through wounds or insect damage and causes fruit to rot and drop rapidly. Rotting fruits on the tree or on the ground often show concentric rings of white or grey spore pustules. Remove all mummified fruits from both tree and ground as they harbour spores that re-infect next year's crop.

Strong wind and physical impact

Heavy rain combined with strong winds can physically knock ripe and near-ripe plums from the tree in August. There is little to do about this except harvest promptly as soon as the fruit approaches ripeness in exposed gardens.