Germination is simply a seed waking up. Inside every seed is a tiny plant and a store of energy, waiting for the right signal to grow. Give it the few things it needs — moisture, warmth and air, plus light for some seeds — and it will sprout. Get one of them wrong and even good seed sits and sulks. Here is exactly what seeds need, how to sow them for the best results, and how to speed things up.
- Moisture steadily damp, never dry or soaked
- Warmth most like 18–22°C
- Air loose, free-draining compost
- Light some seeds need it — check the packet
The things every seed needs
Moisture softens the seed coat and triggers growth, so the compost must stay evenly damp from sowing until the seedling appears — a clear lid or bag helps. Warmth is the engine: most seeds germinate fastest at 18–22°C, which is why a warm windowsill or a propagator beats a cold sill. Air matters too — seeds breathe, so use a light, free-draining seed compost rather than dense, waterlogged soil. And a few seeds need light to germinate and should be left uncovered; the packet will tell you when.
How to germinate seeds, step by step
- Fill & firm seed compost
- Sow seed-width deep
- Water gently or from below
- Cover lid or bag
- Keep warm 18–22°C
- Uncover when sprouts show
Sow at the depth on the packet — as a rule, cover a seed only as deep as it is wide, and leave light-loving seeds on the surface. Keep the compost damp but never soggy, somewhere warm and bright. The moment the first shoots appear, take the cover off and give them as much light as you can so they grow stocky rather than leggy.
How long does germination take?
It varies a lot. Fast crops like radish, beans and many leaves can be up in 3–7 days, while peppers, parsley and some perennials take two to three weeks or more. Always check the germination time on your packet before you worry, and make sure you are sowing in the right season — our sowing calendars show when to sow each type.
How to speed up germination
- Give bottom heat — a propagator or heat mat holds that 18–22°C sweet spot.
- Cover to trap humidity — a clear lid or freezer bag stops the surface drying out.
- Pre-soak large or hard-coated seeds — an overnight soak softens peas, beans, sweet peas and beetroot.
- Use fresh seed compost — fine and free-draining beats old, lumpy mixes.
- Sow in season — the right warmth and light beat any gadget.
Indoors or straight outside?
Tender crops and most flowers germinate best started indoors, where you control warmth and moisture. Hardy, fast crops can be sown direct once the soil warms. If nothing comes up, our guide to why seeds do not germinate walks through every fixable cause.
Common mistakes
- Letting the compost dry out — even once can stop germination.
- Sowing too deep — small seeds need only a dusting.
- Too cold — a chilly room slows everything right down.
- Burying light-loving seeds — some need to sit on the surface.
- Giving up too soon — check the packet time first.
Frequently asked questions
Do seeds need light to germinate?
Most do not and can be covered, but some (like lettuce and snapdragons) need light — the packet will say.
Should I soak seeds before sowing?
Only large or hard-coated seeds really benefit; most small seeds do not need it.
Why are my seeds not coming up?
Usually too cold, too deep, too dry or too old — see our germination troubleshooting guide.
What temperature is best?
Around 18–22°C suits most seeds; a few warmth-lovers like chillies prefer a little more.
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