When to sow tomatoes?
- Botanical name
- Solanum lycopersicum
- Family
- Solanaceae
Tomatoes are sown indoors in March, 1 cm deep. They germinate in 8 to 10 days. They are harvested from July to October.
Tomatoes are annual plants. The edible part is the fruit.
A tomato is never sown directly outdoors. It has no tolerance of frost, so young plants are started indoors. The seed sprouts at 18 to 27 °C. After 6 to 8 weeks of growing on, the young plant moves out a week past the last frost.
The days to the first crop are counted from the move to the bed and not from sowing. One sowing does for the year, because the plant keeps bearing right through. The first autumn frost ends the picking.
Tomatoes through the year
- indoor sowing
- transplanting
- harvest
In short
Growing conditions
Are tomatoes toxic to cats and dogs?
Yes. Toxic to people and animals, toxic parts: stems and leaves.
Companions in the bed
Companion planting is tradition and not an agronomic claim. What is recorded is which pairs sources recommend and which they advise against.
Borage at the edge of the bed is forage for the pollinators. It seeds itself on, so leave it the edge and not the middle.
Corn and tomato share a pest, and the corn takes the tomato's sun.
- “Cited” means the pair is named by one source or two.
- “Sources disagree” means one source recommends the pair and another advises against it.
Pests and diseases
Listed here is every problem for which the sources name this plant as a host. The problems are not listed in order of how common they are.
- Signs
- Colonies of small aphids sit on the shoot tips and the underside of the leaves. The leaf curls and puckers, and sticky honeydew is left on everything below. The viruses they carry are more dangerous than the feeding itself.
- Prevention
- Go easy on nitrogen, because soft sappy growth is what aphids are looking for. Encourage the predators (ladybirds, lacewings, parasitic wasps). Use a reflective mulch, which puts them off settling, and a strong jet of water to knock the colony off the tips.
- What to do
- Potassium soap works on contact and only while it is wet, so it has to reach the underside of the leaf. On drought-loving plants and in heat it can scorch, so apply it in the evening.
- Signs
- At the blossom end of the fruit there is a watery, then dark, sunken and leathery patch. It is not a disease and does not pass from plant to plant, it is a sign that calcium never reached the fruit.
- Prevention
- Even moisture in the soil is the main measure: mulch and deep watering instead of a little and often. No excess nitrogen. Lime after a soil test, so that the calcium in the soil is available at all.
- What to do
- Remove the affected fruit. The next fruits come clean once the moisture steadies. A calcium spray gives temporary relief at best and does not replace watering.
- Signs
- Adult beetles and reddish larvae eat the leaves until nothing is left of the plant but bare stems. Once the foliage runs out they start on the stems as well. The yellow eggs sit in tight clusters on the underside of the leaves.
- Prevention
- Keep to a rotation, because the beetle overwinters in the soil exactly where the attacked crop stood. Lay a thick straw mulch, which makes its way to the plants harder and draws in predators. Look for the egg clusters early, while there are few of them.
- What to do
- Collect and destroy beetles, larvae and egg clusters, often and early in the season. Put the fleece on before the beetles come out of the soil. The aubergine is the beetle's favourite host and can be planted as a trap crop.
- Signs
- Small entry holes in the stem with borings that look like sawdust. Above them the foliage wilts or the stem snaps.
- Prevention
- In autumn remove or shred the stems in which the caterpillars overwinter: cut them off at ground level and mulch them, plough them in or carry them off the bed. This is the strongest measure, because it takes the pest's winter quarters away.
- What to do
- Split the attacked stem below the entry hole and destroy the caterpillar. On a small bed this is workable and more precise than spraying, which does not reach a caterpillar inside a stem anyway.
- Signs
- The leaves are riddled with small round holes, as if somebody had peppered them with shot. Touched, the beetles jump. Young plants with such leaves stall or die, older ones grow through the damage.
- Prevention
- Clear away the plant debris in which the beetles overwinter. Cover the bed with fleece right after sowing or planting and leave it until the plants are strong. Keep the soil moist, because a dry warm spring is the worst case.
- What to do
- Pin fleece down at the edges, which is the main measure. In autumn or early spring loosen the top layer of soil to cut down the number of overwintering beetles.
- Signs
- On the leaves and stems there are dark, watery blotches, spreading fast until the leaf browns and dies. On the underside of a blotch there is a white down. On the fruit there are firm, olive brown patches. In cold wet weather the plant collapses in a few days.
- Prevention
- Plant healthy stock and keep to the rotation. Give the plants a wider spacing and an airy site. Water under the leaves, never over the foliage. Remove diseased plants as they show and take them out of the garden, not onto the compost. Choose resistant varieties.
- What to do
- Copper products work only as a preventive. Once the blotches are visible the disease can no longer be stopped and the only measure is to remove the plant.
- Signs
- Holes appear in the middle of the leaf rather than along the edge, young plants are eaten down to the ground, and there are slimy trails in the morning. On low-growing fruit there are gnawed pits.
- Prevention
- Remove the hiding places beside the bed: boards, stones, dense weeds. Water in the morning and not in the evening, so that the night is dry. Spread a band of coarse sand or gravel around the bed. Cover young plants with fleece. Pick them off at night, which is still the most effective measure.
- What to do
- Baits with iron phosphate are held to carry less risk for pets and children. Put them out in bands beside the bed, not scattered over the whole surface.
Check the registration and the label before use.
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Log the task and set a reminder for the next one. Every plant keeps its own history, so there is nothing to guess at.
Related plants
The plants below are in the same botanical family (Solanaceae).
Sources about the plant: ASPCA Toxic and Non-Toxic Plants, Clemson Cooperative Extension, GBIF Backbone Taxonomy, KGZS, NC State Extension Plant Toolbox, Royal Horticultural Society, Semenarna Ljubljana, Utah State University Extension, Wikidata. Checked between 14 and 28 August 2026. The problem descriptions also draw on: EPPO Global Database, University of Maryland Extension, University of Wisconsin-Madison Division of Extension.