How do I grow flowers from seed?

Growing flowers from seed is cheap and reliable if you get two things right: not overwatering seedlings, and acclimatising them properly before they go outside. Everything else is forgiving.

What you'll need

• Seed
• Seed trays or pots
• Peat-free seed compost
• Watering can with a fine rose
• Propagator lid or clear bag (optional)

Step by step

1. Check the packet for hardy or half-hardy.Hardy annuals — cornflowers, calendula, nigella — can be sown direct. Half-hardy ones like cosmos and zinnia need starting indoors.
2. For direct sowing, wait until the soil has warmed and rake it to a fine tilth.Cold wet soil rots seed. Two weeks of patience usually beats an early sowing.
3. For indoor sowing, fill trays with seed compost and firm it lightly.Seed compost is low in nutrients, which suits germination. Multipurpose is too rich for small seed.
4. Sow thinly and cover to about the depth of the seed's own size.Fine seed needs barely covering. Some need light to germinate — check the packet.
5. Water from below by standing the tray in water until the surface darkens.Watering from above displaces small seed and compacts the surface.
6. Keep them warm and bright but not in scorching sun.A windowsill works. Turn the tray daily or seedlings lean towards the light.
7. Prick out into individual pots once the first true leaves appear.Handle by the leaf, never the stem — a crushed stem is fatal, a damaged leaf is not.
8. Harden off over seven to ten days before planting out.Increasing hours outside each day. Skipping this checks growth badly and kills a lot of seedlings.

Tips

• Damping off — seedlings collapsing at soil level — is caused by overwatering and poor airflow. Water less and give them space.
• Sowing in modules rather than a shared tray avoids root disturbance at pricking out entirely.
• Successional sowing every two or three weeks extends flowering across the season rather than getting one flush.

Common mistakes

• Overwatering seedlings — Damping off is the commonest cause of seedling loss, and it is almost entirely a watering problem.
• Sowing too early — Cold soil rots seed, and leggy indoor seedlings on a dark windowsill do worse than later ones.
• Skipping hardening off — The shock of full sun and wind checks growth severely and kills many seedlings outright.

Questions people ask