How to Grow Tomatoes: From Seed to Harvest

No supermarket tomato comes close to one picked warm from your own plant — and few crops repay a beginner faster. Tomatoes ask for three things: warmth, sun and consistency. Get those right and everything else is detail. This guide takes you from a packet of seeds to a summer of harvests.

Step 1: Choose the right type

Tomatoes come in two growth habits, and the difference decides how you'll grow them. Determinate (bush) varieties stop at a set height, ripen much of their crop at once, and suit pots and small spaces with little pruning. Indeterminate (cordon or vining) varieties keep growing and fruiting until cold stops them — they need a tall stake and regular pruning, but reward you with a long, steady harvest. Cherry varieties are the most forgiving for beginners; beefsteaks demand the most warmth and patience.

Step 2: Sow indoors, 6–8 weeks before the last frost

Tomatoes are tender plants — frost kills them — so in cool climates the season starts on a windowsill. Sow seeds 1 cm deep in moist seed compost. Kept at 21–27°C, they germinate in 7–14 days. After germination, seedlings need strong light: a very bright window works, but 14–16 hours under a grow light prevents the leggy, leaning seedlings a dim sill produces.

Step 3: Pot up and harden off

When seedlings have two or three sets of true leaves, move each into its own 8–10 cm pot, burying the stem up to the first leaves — tomatoes grow roots from any buried stem, and a deeper start means a sturdier plant. A week or two before planting out, harden them off: stand them outside in a sheltered spot for a few hours a day, gradually extending the time, so the move outdoors isn't a shock.

Step 4: Plant out after the last frost

Transplant once all frost risk has passed and nights stay above about 10°C. Choose the sunniest spot you have — tomatoes want at least 6–8 hours of direct sun — with rich, free-draining soil improved with compost, ideally at pH 6.0–6.8. Space bush varieties 45–60 cm apart and cordons 60 cm apart, and again plant deep, burying a third to a half of the stem. Put stakes or cages in at planting time; pushing them in later damages roots.

Step 5: Water and feed with consistency

Irregular watering is behind most tomato heartbreak — split fruit and blossom end rot both trace back to it. Aim for deep, even moisture: roughly 2.5–4 cm of water a week, more in hot spells or pots, delivered at the base of the plant rather than over the leaves. Mulch to hold moisture. Once the first flowers appear, feed weekly or fortnightly with a high-potash tomato fertiliser.

Step 6: Prune and support (cordons only)

On indeterminate varieties, pinch out the side-shoots ("suckers") that sprout in the joint between a leaf and the main stem while they're small, and tie the main stem to its support as it climbs. Late in the season, pinch out the growing tip so the plant ripens what it has instead of making fruit that won't beat the cold. Bush varieties need none of this — just a little support when heavy with fruit.

Step 7: Harvest

Depending on variety, fruit ripens 60–100 days after transplanting. Pick when fully coloured and slightly yielding, or from the "breaker" stage (first blush) onwards — fruit ripens perfectly on a warm counter, and off the vine it's safe from splitting and pests. At season's end, ripen remaining green fruit indoors.

Troubleshooting quick guide

• Blossom end rot (black, sunken fruit bases): calcium shortfall caused by uneven watering — fix the watering, not usually the soil.
• Splitting fruit: a sudden soak after a dry spell; water evenly and pick ripe fruit before heavy rain.
• Yellowing leaves: often nitrogen hunger or overwatering on lower leaves — see our dedicated guide.
• Late blight: brown, fast-spreading lesions in warm, wet weather; remove affected tissue fast and improve airflow.

Not sure what's attacking your plant? Photograph the leaf or fruit in PlantMe and the app's diagnosis model will match it against 500+ diseases and give you a treatment plan.