Why Are My Blackberries Crumbly and Falling Apart?

A blackberry (botanically an aggregate fruit — a cluster of individual drupelets) holds together when all the drupelets are well-developed and full. When individual drupelets fail to develop or are damaged, the fruit becomes crumbly — it falls apart into separate drupelets when picked or handled rather than coming off cleanly as a coherent berry. This problem has two main causes: incomplete pollination during the flowering stage, and internal feeding damage by raspberry beetle larvae.

Incomplete pollination

Each drupelet on a blackberry requires an individual act of pollination to develop fully. The flowers are pollinated by bees, and in a cold, wet or windy flowering period when bees are not flying, some drupelets on each flower head may not receive pollen. These unfertilised drupelets fail to develop properly and remain small and pale, producing a crumbly fruit. The extent of the problem varies with the weather in the specific two-week window when the plant is in flower — it is not consistent from year to year.

Raspberry beetle larvae

Raspberry beetle larvae feeding inside the developing berry damage the structure of individual drupelets, causing them to collapse and pull away from adjacent drupelets. A crumbly fruit that also contains a small cream-white grub when cut open has been affected by raspberry beetle. See the dedicated raspberry beetle guide for timing and control options.

Botrytis on developing fruit

In a wet season, Botrytis infection of developing fruit clusters can cause individual drupelets to collapse and rot before the rest of the cluster is ripe, producing a partially intact, partially crumbled berry. Remove infected clusters promptly to prevent spread to adjacent fruit.

Improving pollination

Avoid applying any insecticides to the plant during the flowering period — even organic sprays can deter or harm pollinators if applied to open flowers. Flowering blackberry plants attract bees and other pollinators naturally; removing other competing interventions during flowering is the most productive step a grower can take to improve fertilisation.