Growing peppers from seed gives you access to varieties that are never available as plants at garden centres — including the full spectrum from mild sweet peppers to the world hottest chillies. Peppers are slow to germinate and need a long growing season, which means starting from seed indoors is not optional in most temperate climates — it is the only way to achieve ripe fruit before autumn.
When to Start
Sow pepper seeds 10-12 weeks before your last frost date, which means January or February in most of the UK and northern US. In warmer climates (USDA zones 9-10), sow in late autumn for a spring crop. Peppers need soil temperatures of 25-30C (77-86F) to germinate reliably — a heat mat placed under the seedling tray dramatically improves germination rate and speed.
Germination
Sow seeds 6mm deep in small individual cells or a seed tray, two seeds per cell, in a seed compost or germination mix. Cover with a propagator lid or cling film to maintain humidity. At 27C, most sweet and cayenne-type peppers germinate in 7-14 days. Superhot varieties (Carolina Reaper, Ghost Pepper, 7 Pot varieties) can take 3-6 weeks even in ideal conditions. Once seedlings emerge, remove the cover and move to full light immediately to prevent etiolation.
Growing On
Once seedlings have their first true leaves, pot on into 9cm individual pots in potting compost. Keep warm — below 15C, pepper growth slows dramatically. Pot on again to a 15-20cm pot once roots show at the base. Peppers are heavy feeders once established — start liquid feeding every 10-14 days when the first flower buds appear, using a tomato fertilizer high in potassium.
Transplanting and Hardening Off
Peppers can go outside after the last frost when nighttime temperatures consistently exceed 12C. Harden off gradually over 10-14 days — start with two hours outside in a sheltered spot and increase daily exposure. Peppers that go directly from a warm indoor environment to outdoor conditions often drop their flowers, setting back the crop by several weeks.
Supporting and Pinching
Pinch out the growing tip once the plant reaches 20-25cm tall to encourage branching and more fruit-bearing stems. Support with a bamboo cane as the plant grows — pepper stems are brittle and snap easily in wind. Each plant can produce 20-50 fruits per season depending on variety and conditions.
FAQ
Why are my pepper seeds not germinating?
Insufficient soil temperature is the most common cause. Pepper seeds need 25-30C to germinate reliably. Room temperature (18-20C) is rarely warm enough. A propagator or heat mat is almost essential for reliable germination, especially for superhot varieties.
How long does it take from seed to ripe pepper?
Sweet peppers typically take 70-85 days from transplant to ripe fruit. Chillies take 80-100+ days, and superhot varieties can take 120-150 days. This is why an early indoor start is essential in temperate climates.
Can I save seeds from peppers?
Yes. Allow a fruit to fully ripen on the plant — well past the eating stage — then dry the seeds completely before storing in a paper envelope in a cool, dry place. Seeds from hybrid varieties will not breed true; seeds from open-pollinated or heritage varieties will.
Do peppers need pollinating?
Peppers are self-fertile — each flower contains both male and female parts. Outdoors, wind and insects handle pollination. Indoors, gently shake the plants or brush flowers with a soft paintbrush to transfer pollen when flowers are open.
How do I get more heat from chilli plants?
Heat (capsaicin production) increases with stress. Slightly reducing water and nutrition in the final ripening period increases capsaicin concentration. Warmer growing conditions also increase heat. Allowing fruit to ripen fully on the plant (red/orange/purple rather than green) produces maximum heat in most varieties.
See also: Spring Planting Guide by USDA Zone and Succession Planting for Continuous Harvests.