Late April–MayStart briefly under cover in individual pots. Ensure you can plant out into warmth after a few weeks.
- Germination and temperature
- Sow in warmth; cold, persistently wet soil increases the risk of failure.
- After emergence
- Give seedlings light immediately after emergence. A dark loft needs suitable grow lights; warmth alone is insufficient. Ventilate and keep the compost moist without saturating it.
- Pricking out and potting on
- Sow in individual pots or deep modules. Do not prick out bare-rooted; move the whole root ball before the roots become restricted.
- Hardening off and planting out
- Gradually acclimatise indoor-raised plants to sun, wind and outdoor temperatures; shelter them again on cold nights. Plant out after the last frost with the whole root ball; install supports beforehand for climbing types.
Prepare climbing support before planting out. Runner beans are also frost-sensitive as young plants.
Sources and use
Royal Horticultural Society · RHS — pronkboon kweken ↗Soort- of productgebonden bron; buitenlandse perioden zijn geen vaste Nederlandse zaaidatum.
University of Maryland Extension · UMD Extension — bonen kweken ↗Soort- of productgebonden bron; buitenlandse perioden zijn geen vaste Nederlandse zaaidatum.
Guideline periods for the Netherlands and Flanders. Check the variety, available light, soil and measured temperatures. Greenhouse heating does not guarantee enough winter light.