Cosmos

Sow seed indoors in March or April at 15-20 degrees Celsius. Seeds germinate in 7-10 days. Harden off and plant out after the last frost in late May. Space plants 30-45 cm apart. Alternatively, sow directly outdoors in May once the soil has warmed. Choose a sunny spot with average to poor soil — rich, fertile ground produces masses of foliage at the expense of flowers. Water sparingly once established; cosmos is moderately drought-tolerant. Pinch out the growing tip when plants reach 20 cm to encourage branching and more blooms. Deadhead regularly to prolong flowering right up until the first frosts. Tall varieties may need staking in exposed positions. Cosmos self-seeds freely in mild areas, with volunteer seedlings appearing the following spring.

Pinch out growing tips when young to encourage bushy growth. Deadhead spent flowers every few days to prevent seed set and extend the flowering season. No other pruning required.