How to grow peppers from seed

When to start seeds

Start pepper seeds indoors 8–10 weeks before your expected last frost date and outdoor transplant date. Because peppers need a long season, starting too late means plants enter the garden behind schedule and may not mature before fall cold arrives.

Hot peppers, especially superhots, can take significantly longer to germinate than sweet peppers — some varieties take up to 6 weeks — so factor this in when planning your start date.

Germination: heat is non-negotiable

Pepper seeds germinate when soil temperature is 70–80°F (OSU Extension); germination is fastest and most reliable at 80–90°F, which typically requires a seedling heat mat. At lower temperatures seeds are slow and erratic.

Plant seeds 1/4 inch deep in a sterile, soilless seed-starting mix — not garden soil, which drains poorly and can harbor disease. One or two seeds per cell is sufficient; with older seed of uncertain viability, sow 2–3 per cell and thin later.

1. Fill cells or flats with moistened seed-starting mix.
2. Sow seeds 1/4 inch deep; cover lightly and firm the surface.
3. Place tray on a heat mat set to 80–90°F.
4. Cover with a humidity dome to retain moisture; check daily and keep mix evenly moist.
5. Expect germination in 7–21 days for most varieties; superhots can take up to 6 weeks.
6. Remove the dome immediately once seedlings emerge.

Light after germination

Once sprouts appear, strong light is the priority. A windowsill rarely delivers enough intensity or duration; use a horticultural grow light positioned a few inches above the seedlings, running 14–16 hours per day (UC ANR/Stanislaus).

To prevent weak, leggy stems, run a small fan on the lowest setting for a few hours each day. Gentle air movement also discourages damping-off fungus.

Seedling care: watering and pinching

Water from the bottom by adding about 1/4 inch of water to the tray and allowing the mix to wick it up. Let the mix dry slightly between waterings — pepper roots dislike standing in wet media.

When seedlings are 4–5 inches tall (around 6–8 weeks), reduce watering slightly to encourage stronger roots. Pinch off any flower buds that form on seedlings before transplanting; allowing the plant to fruit before it is established in the ground reduces final yield (UMN Extension).

Hardening off

Begin hardening off 7–14 days before your planned transplant date, once daytime temperatures are consistently above 60°F. Abrupt exposure to wind, direct sun, and temperature swings stresses or damages plants.

Never expose seedlings to temperatures below 45–50°F during hardening; chilling can set back or permanently stunt pepper plants.

1. Days 1–2: Place plants in a sheltered, shady spot outdoors for 2 hours, then bring inside.
2. Days 3–7: Gradually increase outdoor time and sun exposure each day.
3. Days 8–14: Leave plants outdoors all day; bring in if nighttime lows are forecast below 50°F.
4. By the end of 2 weeks, plants can stay outside around the clock when nights stay above 50°F.

Transplanting to the garden

Transplant outdoors only after nighttime temperatures are reliably above 50°F and soil temperature has reached at least 65°F — planting into cold soil causes plants to stall (UMN Extension). Set plants 18–24 inches apart in rows 30–36 inches apart (UMN/OSU Extension).

Plant at approximately the same soil-line depth as in the container, or up to 1/2 inch deeper. Water in well at transplanting. Soil pH should be 6.0–6.8 (OSU Extension); amend before planting if needed.