Starting Seeds Indoors: A Beginner’s Timeline

By Owen Petrakis · Published Sep 15, 2026 · 6 min read

In this guide

Find your last frost date
Typical timings
Light is the limiting factor
Pot on and harden off
Keep it hygienic

Starting seeds indoors gives frost-tender crops like tomatoes and peppers a head start, so they produce more before the season ends.

Start too early and you get leggy, weak seedlings. Start too late and the harvest comes too late. A timeline solves both problems.

Find your last frost date

Look up the average last frost date for your area from a local gardening organisation or extension service. Every seed timing decision counts back from it.

Typical timings

Peppers and chillies: 8–10 weeks before last frost
Tomatoes: 6–8 weeks before
Brassicas such as broccoli and cabbage: 6–8 weeks before
Courgettes, squash, and cucumbers: 3–4 weeks before — they grow fast
Beans and peas: often best sown directly outdoors

Light is the limiting factor

Seedlings on a windowsill often stretch toward the glass and become pale and spindly. A simple LED grow light hung a few centimetres above them for 14–16 hours a day produces sturdy, compact plants.

Pot on and harden off

Move seedlings into individual pots once they have their first true leaves. A week or two before planting out, harden them off: put them outside for a few hours each day in a sheltered spot, increasing the time gradually, so they adjust to sun, wind, and cooler nights.

Keep it hygienic

Use fresh seed compost and clean trays to reduce damping off, a fungal disease that makes seedlings collapse at the base. Water from below where possible, and give seedlings good airflow.

This is general gardening information. Results depend on your climate, soil, and conditions. Follow label directions for any fertiliser or treatment, and check whether plants are toxic to pets or children before bringing them home.

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