When to plant Zinnias in Cardiff

Sow seeds in modules around 15th April - 29th April, about 1 cm deep in fine compost. Keep them warm and bright, and water lightly so the compost stays just moist.

Pot seedlings on around 29th April - 20th May, as soon as they have their first pair of true leaves. Move them into individual small pots so the roots do not become cramped, and keep them warm in good light without overwatering.

Harden plants off over 15 days before planting out, from 13th May to 27th May. Put them outside during the day at first, then bring them in at night until they cope with cooler air and brighter sun.

Plant out around 27th May - 10th June into fertile, free-draining soil in a warm, sunny, sheltered position, spacing plants 30 cm apart. Water in thoroughly straight away, and protect young plants from slugs.

From 27th May to 28th October, water at soil level during dry spells and avoid wetting the leaves, as damp foliage encourages fungal disease. Once flowering begins, feed plants in containers with a high-potash liquid feed according to the label.

Around 10th June - 8th July, pinch out the main growing tip above a pair of leaves when plants are 20–30 cm tall to encourage branching. Support tall cultivars with canes or netting before the stems become top-heavy.

Every 14 days from 8th July to 28th October, cut flowers for the house or remove fading blooms back to a leaf joint. Regular cutting and deadheading encourage the plants to keep producing flowers until frost.