Starting Seeds Indoors: A Step-by-Step Guide

Starting seeds indoors is part science, part patience. The reward is a wider choice of varieties, healthier transplants and a garden that hits the ground running when the weather finally warms.

Work backwards from your last frost

Read the seed packet. Tomatoes are usually started 6–8 weeks before the last expected frost; peppers and aubergines need 8–10 weeks; brassicas and lettuce can be started closer to 4–6 weeks. Starting too early produces leggy, stressed plants.

Gather the basics

• Clean trays or pots with drainage holes.
• A light, sterile seed-starting mix.
• A bright window or, better, a simple LED grow light.
• A tray cover or humidity dome.
• A heat mat for warmth-loving seeds.

Sow with care

Moisten the mix before filling containers. Sow at the depth recommended on the packet — usually two to three times the seed's diameter. Label everything. Keep the surface warm and damp until germination, then remove the cover and move seedlings into bright light immediately.

Light is the limiting factor

Windowsill light is often weaker than it looks. Seedlings that stretch and lean are begging for more light. Keep a grow light 5–10 cm above the leaves and raise it as plants grow. Aim for 14–16 hours of light per day.

Pot on and harden off

When seedlings have two sets of true leaves, move them into larger pots. About a week before planting out, begin hardening off: expose plants to increasing time outdoors, starting in shade and shelter and gradually introducing sun and wind.

Avoid common mistakes

Do not overwater; damp-off disease thrives in soggy, cool conditions. Do not fertilise too early — seed-starting mix usually has enough for the first few weeks. And do not rush the outdoor move; a late frost can erase weeks of work.