Why Are My Raspberry Canes Wilting During Hot Dry Weather?

Raspberry canes wilting in the midday heat of a dry summer, and sometimes not fully recovering overnight, are suffering from drought stress. Raspberries have a shallow, fibrous root system concentrated in the top 30cm of soil — they cannot access deep moisture reserves in the way that deep-rooted trees can, and are therefore significantly affected by dry spells, particularly during the critical period of fruit development when the demand for water is at its highest.

How much water do raspberries need?

During flowering and fruit development — roughly May to July for summer varieties — raspberries benefit from the equivalent of 25mm of water per week. If rainfall provides less than this, irrigation makes up the difference. This sounds like a lot, but the critical period is relatively short (six to eight weeks), and the payoff in fruit size, yield and quality is significant. Outside this period, established raspberry rows are reasonably drought-tolerant.

Mulching to conserve moisture

A thick mulch — 7–10cm of bark chippings, straw or garden compost — applied along the row in late spring dramatically reduces soil moisture loss in summer. Mulch keeps the soil cool, reduces evaporation and protects the shallow root system from drying out between waterings. Ensure the mulch does not touch the cane bases directly to avoid encouraging crown rot.

Watering method

Water at the base of the row directly onto the soil — overhead sprinkler irrigation wets the foliage and fruit, which promotes disease. Drip irrigation or a soaker hose running along the base of the row is the most efficient method. Water deeply and infrequently rather than lightly every day — this encourages roots to reach down further and makes the plants more resilient to dry periods.