Growing Tomatoes: From First Sowing to the Last Ripe Fruit

Tomatoes are usually the first thing a new gardener grows, and there's a good reason experienced ones keep coming back to them: few crops give back so much for the space. But a tomato is a long-season plant pretending to be an easy one. Everything that follows — when you sow, how you plant, whether you prune, how you water — comes back to a single fact: from the day you sow to the day you pick a ripe fruit is a long stretch of warm weather, and most of us are working against the calendar. Get the timing and the consistency right and tomatoes are generous to a fault. Rush them, or let them dry out and flood in turns, and they'll sulk. So this is the whole arc, in order.

Starting from seed

Tomatoes are almost always started indoors, weeks before it's warm enough to plant them out, precisely because the season is the constraint. Sow into small pots or trays of moist seed compost, barely covering the seed, and keep them somewhere warm — around 20°C is plenty — until they germinate, which usually takes a week or so. The moment they're up, the priority flips from warmth to light: a seedling on a dim windowsill stretches into a pale, leggy thing reaching for the glass. Give them the brightest spot you have, or a grow light, and turn them daily so they grow straight and stocky.

How many weeks before your last frost you sow depends entirely on where you garden — too early and you're nursing root-bound plants indoors for weeks, too late and you're still waiting on green fruit when autumn arrives. Use the planner to work back from your own frost date rather than a generic rule of thumb; a short-season gardener and a greenhouse grower are playing different games.

Planting out

Don't rush this step — a tomato checked by a cold night in May will trail one that waited a week and grew away happily. Wait until the nights are reliably warm and all danger of frost has passed, and harden the plants off first: a week or so of increasing time outdoors so they toughen up before they're planted for good.

When you do plant, do two things the plant will thank you for. Give them room — crowded tomatoes trap damp air and invite disease, so space them generously. And plant them deep: tomatoes grow roots all along any buried stem, so setting a leggy plant in right up to its lowest leaves turns that weak stem into a bigger, stronger root system. It's the one time burying part of a plant is exactly the right move.

Support and pruning: the one decision that matters

Here's the fork that decides how you'll treat the plant all season, and it's not optional homework — it's the difference between a tidy productive plant and a sprawling mess. Tomatoes come in two habits, and your variety is one or the other.

• Indeterminate (cordon / vine) types grow a single main stem upward, more or less forever, flowering and fruiting as they go. These need a tall support — a cane, string, or stake — and they benefit from suckering: pinching out the side-shoots that form in the join between the main stem and each leaf, so the plant pours its energy into fruit up the main stem instead of turning into a bush. Do this little and often while the shoots are small.

• Determinate (bush) types grow to a set size, set their fruit over a short window, and stop. These you largely leave alone — do not sucker them, or you'll cut off the very shoots that carry the crop. A short stake or a cage to keep them off the ground is all they need.

Suckering a bush tomato is one of the most common ways gardeners quietly ruin their own harvest, so it's worth knowing which one you've got before you pick up the scissors. Most catalog varieties tell you their habit — a cherry like Sungold or an old cordon like Moneymaker is indeterminate and wants suckering; a paste type such as Roma VF is typically determinate and doesn't. When in doubt, check the variety's own page in the catalog.

Watering and feeding: consistency over quantity

If there's one thing that separates good tomatoes from disappointing ones, it's even watering. Tomatoes hate feast-and-famine: let the soil dry hard and then soak it, and the fruit responds by splitting, or by developing blossom-end rot — that sunken dark patch on the base — which is really a symptom of calcium not moving through a plant whose water supply keeps lurching. The fix isn't more water, it's steadier water: deep, regular drinks, and a mulch to hold moisture between them so the plant never swings from bone-dry to flooded.

Feeding follows the plant's own timeline. While it's building leaves and stems, ordinary soil is usually enough. Once flowers set and fruit starts to swell, switch to a feed higher in potassium — a tomato feed — to support fruiting rather than yet more foliage. Feed too much nitrogen too late and you'll grow a magnificent leafy plant carrying very few tomatoes.

Harvesting and ripening

Pick tomatoes as they colour up and give slightly to a gentle squeeze — a fruit ripened on the plant almost always beats one ripened off it, so leave them as long as the season allows. A truss picked with a little stem attached keeps a touch longer.

Then the season turns, as it always does, and you're left with a plant full of green fruit and the first cold nights coming. Don't panic and don't leave them to rot in the cold: pick the mature green fruit and ripen it indoors — on a windowsill, or in a paper bag with a ripe banana or apple, whose ethylene nudges them along. Late in the year you can also help the outdoor plant by removing its lowest, shadiest leaves to open up airflow and let light onto the ripening trusses — the same late-season tidy that helps chilies finish. What won't ripen at all still isn't wasted: green tomatoes are a crop in their own right, for chutney and frying.

Grow them with a bit of patience and a steady hand on the watering can, and tomatoes will out-give almost anything else in the garden. Check your variety's real timeline and habit in the catalog, plan your sowing against your own season in the planner, and let the plant set the pace.

— Pernille