Sowing, potting on, and transplanting

Sow indoors in late March or early April. Fill small pots or modules with seed compost, water from below until the surface darkens, sow two seeds per cell 1cm deep, cover, and place somewhere warm. Germination takes 6–10 days at 20°C. The moment the first shoot appears, move to the brightest windowsill or under a grow light. Remove the weaker seedling once both are 5cm tall.

Pot on when the first true leaves are fully open and roots are visible at drainage holes — usually 3–4 weeks from sowing. Use 9cm pots and multipurpose compost. Water in gently. Harden off in mid-May: move pots outside during the day, inside at night, for a week. Tomatoes are frost-tender — one cold night below 5°C will check growth for weeks.

Transplant into final pots in late May or early June once night temperatures stay above 10°C. Use a 30–35cm pot per plant, filled with good-quality peat-free multipurpose or a 50:50 mix of multipurpose and soil-based compost (John Innes No. 3 adds weight and structure). Bury the stem up to the first true leaves — tomatoes root along the buried stem, creating a stronger plant. Water in thoroughly.