How to Grow Tomatoes: Determinate or Indeterminate First

Almost every tomato guide starts with sun and water. Those matter, but the decision that shapes everything else is printed on the seed packet in one word, and most people read past it: determinate or indeterminate.

Get that right and the spacing, the support, the pruning, and the shape of your harvest all follow. Get it wrong and you will prune a bush tomato until it has nothing left to fruit on.

The one word that decides everything

Packets sometimes use “bush” for determinate and “cordon” or “vine” for indeterminate. If it says nothing at all, assume indeterminate — most heirlooms are.

Starting and planting

Sow six to eight weeks before your last frost, a quarter-inch deep, somewhere warm — germination is driven by soil temperature, and 70–80°F is what you want. Light matters only once they emerge, at which point it matters a great deal: weak light produces stretched, floppy seedlings that never fully recover.

Pot on as they grow and bury the stem deeper each time. Tomatoes are one of the few crops that root along a buried stem, so this is free root system.

Plant out only when nights are reliably above 50°F. There is no prize for being early; a plant set into cold soil stalls, and a later one usually overtakes it.

Support goes in on planting day

Whatever you use — stake, cage, or string from an overhead wire — put it in when you plant. Driving a stake in beside an established plant tears through the root ball you spent weeks building.

Indeterminate plants need something genuinely tall; they will run past 6 feet given a season. The flimsy conical cages sold as tomato cages are usually adequate for determinate types and comically undersized for indeterminate ones.

Water, and the two problems it causes

Tomatoes want consistently moist soil. Not wet, not swinging between drought and flood — consistent. Deep soaking two or three times a week, with two to three inches of mulch on the surface, is the whole method.

Two very common complaints trace directly back to inconsistent water rather than to anything else:

• Splitting fruit — a dry spell followed by heavy water makes the inside swell faster than the skin can stretch.
• Blossom end rot — the dark sunken patch on the base is a calcium availability problem, and erratic watering is what stops the plant moving the calcium it already has. Adding calcium rarely fixes it; watering consistently usually does.

Water at the base rather than over the leaves, and in the morning, so any splashed foliage dries.

Pruning, but only the right type

On indeterminate plants, side shoots form in the joint between the main stem and each leaf. Pinch them out while they are small. Left on, the plant becomes a dense thicket that shades its own fruit and holds damp air in the middle.

On determinate plants, do not do this. Their fruit forms on those very branches, and pruning them removes the crop.

Late in the season, on indeterminate plants, pinch out the growing tip a few leaves above the topmost truss you expect to ripen. That stops the plant starting fruit it has no time to finish.

The problems worth recognising early

Leaves curling upward, plant otherwise fine. Usually harmless physiological leaf roll — see tomato leaves curling for what separates it from the serious causes.

Flowers dropping without setting. Night temperatures outside roughly 55–75°F, or very dry air. Tapping the stem or a gentle shake helps pollination in still conditions.

Brown blotches spreading fast in warm, wet weather. Blight. Remove affected material promptly, improve airflow, and choose resistant varieties next year.

White powder on the leaves. Powdery mildew — spacing and airflow first, treatment second.