How to Plant Tomatoes: Choosing Transplants and Planting Depth

What to look for in a transplant

Choose a tomato plant whose first flower truss, the first cluster of buds, is just starting to show. A plant with no sign of flower yet is too young: it will put its energy into leaves for weeks before it sets any fruit. A plant that has already finished flowering and is carrying small fruit is past its best, and its roots will be slow to take hold in your soil.

The stem should be about as thick as a pencil or a little thicker. A thin plant with long gaps between the leaf joints was grown in poor light. It will flop over after planting and it will be more prone to disease. Look for dark green leaves with no yellowing on the lowest pair.

1. Find the first flower truss On a tomato the first truss forms above the seventh to ninth true leaf. If you can see buds there, the plant is at the right stage to go out.
2. Slide the rootball out and look Ease the rootball out of the pot. You want white roots working their way around the outside. Lots of brown root means it has been overwatered or has sat in the pot too long.
3. On a grafted plant, check the union Grafted tomatoes should have a firm, fully healed join below the clip. If the top wobbles against the rootstock it can snap after planting.

Grafted plants cost two to three times as much, but on ground where you have grown tomatoes before, or where bacterial wilt has appeared, they usually work out cheaper in the end.

Plant by soil temperature, not air temperature

Tomato roots stop growing once the soil drops below about 60F (15C). A warm afternoon in spring is misleading: the ground is still cold underneath, and a plant set out too early simply sits there getting weaker while the roots do nothing. Wait until your last frost date has passed and the soil has warmed.

Laying black plastic mulch over the bed a week before planting raises the soil temperature by five to nine degrees F (three to five C). Do not plant the day after you lay it. Give the soil a few days to warm through and the plants will take hold much faster.

Trench planting builds a bigger root system

Tomatoes grow roots from the buried part of the stem. If your plant is leggy or simply tall, lay the stem down at an angle and bury it up to the lowest remaining leaves. The buried section roots along its length, which anchors the plant and makes it far more tolerant of dry spells.

Trench planting does cost you a few days of growth at the start. If the plant is short and sturdy, plant it normally with the top of the rootball level with the soil surface. What you should never do is plant deep without laying the stem down, because a stem buried upright in cold, wet soil tends to rot.

1. Strip the lowest two or three leaves Remove any leaf that will end up underground. Buried leaves rot, and the rot can travel into the stem.
2. Dig a sloping trench Make the hole deep enough for the rootball, then run a shallow trench away from it for the stem. Lay the plant so the flower truss faces the path.
3. Firm the soil gently Cover the rootball and stem and press with your palm. Too hard and you crush the rootball, too light and the stem dries out instead of rooting.
4. Water it in thoroughly Soak the base straight after planting so the rootball and the surrounding soil knit together. After that, wait until the surface dries before watering again.

Face the flower truss towards the path

Every truss on a tomato plant forms on the same side of the stem as the first one. If you turn that first truss towards the path as you plant, every tomato on the plant will hang where you can reach it, and you will never have to lean into the middle of the row to pick or to check for problems.

It costs nothing to do and it saves you time at every single visit. It also means the fruit gets more light and air, which helps it ripen evenly and dries the plant faster after rain.

Spacing and containers

In open ground, allow 18 to 20 inches (45 to 50 cm) between plants grown on a single stem. Any closer and the leaves stay wet after rain, which is how blight gets started. If you are growing two stems per plant, allow 24 inches (60 cm).

In containers, the limit is the amount of compost, not the size of the pot rim. One plant needs at least five to eight gallons (20 to 30 liters) of compost to get through a hot summer without wilting twice a day.

If something goes wrong in the first fortnight

Leaves that never perk up, lower leaves turning yellow, and stems going purple are the three complaints you are most likely to see after planting, and they have different causes. Check soil temperature and watering first, and only then start thinking about root damage.

1. The whole plant wilts and does not recover The roots are not working. Either the soil is too cold or you have overwatered. Mulch the bed, hold off on water and let the soil dry out a little.
2. Only the bottom leaves yellow The rootball dried out at some point, or the plant is hungry. Water the base thoroughly, and if it does not pick up, give it a weak liquid feed.
3. Stems and leaf undersides turn purple Cold soil is stopping the plant taking up phosphorus. It corrects itself as the soil warms, so wait rather than reaching for fertilizer.
4. It fell over the day after planting The rootball is proud of the soil or the wind is rocking it. Firm the base again and retie it loosely to a temporary cane.