How to Grow Tomatoes: From Seed to Harvest, A Complete Guide

The first decision is the most important. Tomato varieties fall into two fundamental categories:

**Determinate (bush) varieties:** Grow to a fixed height (60–120cm), set all their fruit within a concentrated period, then stop. Lower maintenance, no need for support, ideal for containers or small spaces. Best varieties: 'Tumbler', 'Maskotka', 'Roma' (great for sauce), 'Celebrity'.

**Indeterminate (cordon/vining) varieties:** Grow continuously until frost kills them — potentially 2–3m tall. Require staking, regular pruning of side shoots ('suckers'), but produce fruit over a much longer season. Best flavour, highest yield. Best varieties: 'Sungold' (cherry, orange, exceptional sweetness), 'Gardener's Delight' (cherry, reliable), 'Brandywine' (large heirloom, extraordinary flavour), 'San Marzano' (plum, for cooking).

For beginners: start with a cherry variety (Sungold or Gardener's Delight). Cherry tomatoes are more forgiving, ripen faster, produce continuously, and the flavour is reliably excellent even in a mediocre summer.

**From seed:** Start indoors 6–8 weeks before your last frost date. Sow into small cells or modules, 5mm deep, in seed compost. Keep at 20–25°C — a heated propagator is ideal but a warm windowsill works. Germination: 5–10 days. When seedlings have 2 true leaves, pot on into 9cm pots. When plants are 15–20cm tall with a stocky stem, they're ready to move outdoors.

**Buying transplants:** Far easier for beginners — garden centres sell tomato transplants from late spring. You lose variety choice but gain 6–8 weeks. Look for short, stocky plants with dark green leaves — avoid leggy, pale or root-bound plants.

**Hardening off:** Whichever you choose, tomatoes raised indoors must be 'hardened off' before planting outside. Place plants outdoors in a sheltered spot during the day, bring them in at night, for 7–10 days. This gradually acclimatises them to temperature fluctuations, wind and UV — plants moved directly from indoor to outdoor conditions suffer significant shock.

**Soil:** Tomatoes are heavy feeders and deep rooters. In-ground beds: incorporate a thick layer of compost (10cm) and a balanced granular fertiliser before planting. In containers: use a high-quality peat-free potting mix — change it completely each year to prevent disease build-up.

**Container size:** Minimum 30L per plant for indeterminate varieties; 15–20L for cherry varieties. Under-potting is the most common container tomato mistake — small pots dry out quickly and restrict root development.

**Feeding:** Once the first flowers appear, switch from a balanced feed to a high-potassium tomato fertiliser (look for NPK ratios emphasising K, like 4-4-8 or similar). Feed every 7–14 days throughout the season. Potassium drives fruit development, sweetness and disease resistance.

**Watering:** Consistent, deep watering is essential. Irregular watering — periods of drought followed by overwatering — causes blossom end rot (calcium deficiency caused by inconsistent uptake) and fruit splitting. Water at the base, not the foliage. In warm weather, container tomatoes may need watering daily.

Indeterminate tomatoes produce 'suckers' — side shoots that grow at 45° angles between the main stem and leaf stems. Left unpruned, these develop into full branches, creating a plant that channels energy into vegetation rather than fruit.

The technique: train to a single main stem (or two, for more experienced growers). Pinch out suckers when they're small (under 5cm) — they snap off cleanly. Once they exceed 5cm, cut with clean scissors to avoid tearing the stem. Remove any suckers below the first flower truss entirely.

Top the plant (cut the growing tip) in late summer — typically 4–6 weeks before your first expected autumn frost. This redirects energy into ripening existing fruit rather than producing new growth that won't mature before cold arrives.

Determinate varieties require no pruning — removing growth from bush tomatoes reduces yield.

**Blight (Phytophthora infestans):** The most serious tomato disease — brown patches appear on leaves, then fruit. Prevention: grow in sheltered positions with good airflow, avoid wetting foliage, remove infected material immediately. Growing under cover (greenhouse, polytunnel) dramatically reduces risk.

**Blossom end rot:** Black leathery patch on the base of fruit. Caused by calcium deficiency due to inconsistent watering, not lack of calcium in soil. Fix: consistent, regular watering.

**Greenback:** Green or yellow hard patches on ripe fruit, usually around the stem. Caused by excessive direct sun and heat on fruits. Provide light shade in very hot periods.

**Whitefly:** Common greenhouse pest. Yellow sticky traps catch adults. Encourage natural predators. Biological control (Encarsia wasp) is effective in enclosed spaces.