When to Plant Tomatoes
The date on the seed packet is nearly useless. What matters is soil temperature and your last frost date. Here is how to work it out properly.
The two numbers that matter
- Soil temperature above 10°C / 50°F — below this, roots do not grow and the plant stalls
- Night temperatures above 7°C / 45°F — colder nights cause blossom drop and purple, stunted leaves
Tomatoes planted into cold soil do not just grow slowly — they often never catch up with plants set out two weeks later.
Work it out from your last frost
| Stage | Timing |
|---|---|
| Start seed indoors | 6–8 weeks before last frost |
| Pot on / harden off | 2 weeks before planting out |
| Plant out (with protection) | 1–2 weeks before last frost |
| Plant out (open ground) | 1–2 weeks after last frost |
Rough dates by climate
| Climate | Start indoors | Plant out |
|---|---|---|
| Cold / short season (USDA 3–4) | Late March | Early June |
| Temperate (USDA 5–6) | Mid March | Late May |
| Warm (USDA 7–8) | February | Mid April |
| Hot / subtropical (USDA 9–10) | Autumn planting instead | February or September |
In very hot climates tomatoes are a cool-season crop: they set fruit poorly above 32°C / 90°F. Plant in autumn or late winter and finish before the worst heat.
Why planting early backfires
- Cold soil stalls root growth; the plant sits and yellows
- Nights below 10°C cause blossom drop — flowers form but no fruit sets
- Cold-stressed seedlings are more prone to disease
- Leggy indoor seedlings kept waiting become weak and spindly
How to cheat two weeks earlier safely
- Warm the soil first — black plastic over the bed for 2 weeks before planting
- Use a cloche or wall-of-water — raises night temperature around the plant by several degrees
- Plant deep — bury the stem up to the first true leaves; tomatoes root along the buried stem
- Harden off properly — a week of gradually increasing outdoor time, or the plants scorch
Determinate vs indeterminate
- Determinate (bush) — grows to a set size, crops once, good for containers and short seasons
- Indeterminate (cordon) — keeps growing and fruiting until frost, needs staking and pinching
Common questions
What is the best month to plant tomatoes?
In most temperate climates, late May to early June — one to two weeks after the last frost, once soil is above 10C.
Can you plant tomatoes in cold soil?
You can, but they stall. Roots do not grow below 10C and the plant often never catches up with later plantings.
Why are my tomato flowers falling off without fruit?
Usually night temperatures below 10C or above 24C, or inconsistent watering. Blossom drop is temperature-driven more often than nutrient-driven.
How deep should you plant tomatoes?
Bury the stem up to the first set of true leaves. Tomatoes grow roots along the buried stem, which makes a stronger plant.
Soil mix ratios and bed layouts for tomatoes: Raised Bed Soil Calculator and How Deep Should a Raised Bed Be.