How Do I Start Peppers Indoors from Seed?

Peppers are slower-growing than tomatoes and need a longer season, which means they need to be started indoors earlier than almost any other vegetable. Get the start right and you will have productive plants all summer. Skimp on warmth or timing and you will be chasing lost weeks all season long.

When to Sow Pepper Seeds Indoors

Sow peppers 10–12 weeks before your last expected frost date. In the UK this typically means late January to mid-February. In the US, January or early February is right for most zones. This long lead time accounts for their slow germination (10–21 days) and slow initial growth. Unlike tomatoes, which grow quickly, pepper seedlings develop steadily rather than rapidly — they need the extra weeks.

Germination: Temperature Is Everything

Peppers are among the most temperature-sensitive seeds for germination. They need 24–28 °C (75–82 °F) at compost level to germinate quickly. Below 20 °C (68 °F) germination becomes very slow; below 15 °C (59 °F) most pepper seeds will not germinate at all. A thermostatically controlled heated propagator is more useful for peppers than for any other vegetable. Set it to 25–27 °C, sow seeds 5 mm deep, cover, and expect germination in 10–14 days. Without heat, the same seeds might take 4–6 weeks or fail entirely.

After Germination

Remove the propagator lid immediately when seedlings emerge and move to a very bright spot. Pepper seedlings grow slowly at first — this is normal. They need good light (16 hours per day if using grow lights) and temperatures no lower than 16 °C overnight. Do not rush potting on: peppers are happy in small pots while they are still small plants. Move to a 9 cm pot when the roots reach the pot edges, then pot on again before planting out.

Feeding Peppers During the Indoor Phase

Once peppers have their third or fourth pair of true leaves, begin dilute liquid feeding with a balanced fertiliser (half the recommended strength) once a week. They are light feeders compared to tomatoes but benefit from regular, dilute nutrition once seed compost is exhausted.

Planting Out

Peppers are more frost-sensitive than even tomatoes. Do not plant out until night temperatures are reliably above 12 °C (54 °F) and all frost risk is completely past. In most of the UK this means mid to late May; in the US, after your last frost date plus two weeks of warm nights. Harden off for 2 full weeks before planting out — pepper leaves scorch badly if moved from indoors to full sun too quickly.