For earlier blooms, start tubers indoors about 4-6 weeks before the last expected frost. Plant tubers horizontally in pots with good draining compost, about 5-10 cm (2-4 inches) deep, with any visible 'eyes' or sprouts pointing up. Water very sparingly until growth appears. Keep in a bright, frost-free place (around 15-20°C).

Plant tubers or started plants outdoors after all danger of frost has passed and the soil has warmed (typically late May in the UK). Choose a site with full sun (6+ hours) and well-drained soil. Dig a hole about 15 cm (6 inches) deep, amend with compost. Place tuber horizontally with eyes pointing up. Cover initially with 5-10 cm (2-4 inches) soil. Insert stakes for tall varieties now.

For varieties growing taller than 60-90 cm (2-3 ft), provide support with stakes, cages, or netting. Install supports early. As the plant grows, loosely tie the main stems to the support at intervals.

Once growth is active (shoots are visible and growing), water dahlias deeply 1-2 times per week, more often during hot, dry spells or if in containers. Aim for consistent moisture, but ensure good drainage to prevent tuber rot.

When plants reach about 30-40 cm (12-16 inches) tall and have 3-4 sets of leaves, pinch out the central growing tip just above a leaf node. This encourages branching, leading to a sturdier plant with more flowers.

Dahlias benefit from regular feeding. Once plants are established (around 30 cm tall), apply a liquid fertilizer low in nitrogen and high in potassium (like tomato feed) every 2-4 weeks until early autumn. Avoid high-nitrogen feeds which promote leaves over flowers.

Remove spent flowers promptly throughout the blooming season by cutting the stem back to a main stem or leaf node. This encourages the plant to produce more blooms and prevents seed formation.

Inspect plants regularly for pests like slugs/snails (on young growth), earwigs (in blooms), aphids, and spider mites. Watch for diseases like powdery mildew. Ensure good air circulation.

In autumn, after the first frost blackens the foliage, cut stems down to 15 cm (6 inches). Carefully dig up the tubers, trying not to damage them. Gently remove excess soil (do not wash). Allow tubers to dry for a few days in a cool, airy, frost-free place. Store in boxes filled with slightly damp compost, sand, or vermiculite in a cool (4-10°C), dark, frost-free location.