Caring for dark-leaved dahlias

Dahlias are not difficult to cultivate, providing they are grown in full sun and in well-drained soil enriched with compost. The tubers are planted in spring, in multi-purpose potting compost, in generous 3-litre pots that are placed in a greenhouse or on a sunny windowsill. An alternative approach is to wait until all danger of frost has passed and plant directly into well-dug, humus-rich soil. The hole should be deep, with added compost and a cane support. Taller varieties should be planted 31-35in (80-90cm) apart, ensuring good air circulation between plants to help deter mildew. Mulching well will retain moisture. It is recommended that all but the five healthiest shoots sprouting from the tuber are removed and growing tips pinched out to encourage bushy, well-branched plants. In the summer, developing tubers should be drenched well and watered regularly throughout the growing season: daily during hot spells for pot-grown dahlias. A single tuber can produce dozens of flowers, so a weekly feed with a tomato fertiliser during the growing season is recommended. Deadheading the plant regularly will help to prolong flowering. Placing cut dahlias in a bucket of water overnight allows any resident earwigs to depart. At first frosts, the blackening foliage should be cut to within 6in (15cm) of the tubers. In cold regions of the country or in gardens on clay or with wet soil conditions, it is recommended to lift and store tubers upside down in boxes of dry sand, in a dry, frost-free shed. Alternatively, the tubers can be grown in a large plastic pot that is countersunk into the ground in spring, then lifted in autumn. They can either be overwintered on a sheltered, sunny patio or moved into an unheated greenhouse. In warmer regions, tubers can be left in the ground, covered with a deep, dry mulch to protect against frost. The ground should be marked with labels to indicate where the tubers are planted.