Hardening off new plants

Move plants to a coldframe [link] about two or three weeks before you intend to plant them out. Hardy plants such as spring bedding can be moved out to the coldframe as soon as they are large enough. Tougher summer bedding plants, such as alyssum, can be moved out a month before the last frost date in your area [link to weather]. Tender plants such as begonias, Busy Lizzie and pelargoniums should not be placed into the coldframe before the last expected frost date.

Harden-off the plants by gradually getting them acclimatised to the weather conditions outside. To start with ventilate the coldframe by opening the lid slightly on warm still days only, closing it at night. After a few days, gradually increase the amount of ventilation each day until you remove the lid completely. Replace the lid on cold nights for the next week or so, but then remove it permanently.

If you do not have a coldframe, you can harden-off plants successfully in a sheltered spot at the base of a south-facing wall or hedge. To start with bring the plants in at night. After a week, leave them outside on all but the coldest nights, but cover with a double-layer of garden fleece on other nights.

Tools required

coldframe or garden fleece

Skill rating

moderate