Hardening sweet peas

Sweet peas that were sown under cover in January can start to be hardened off now. These are actually very hardy plants, and autumn-sown seedlings can survive the winter outdoors. But newly germinated seedlings, which were started with a little heat in January should now be slowly acclimatised to outdoor conditions. Put the pots of seedlings in a cold frame with the top closed. After a few days open the vents during the day but shut them at night. After a few more days leave the vents open at night as well, and a few days after that remove the lid completely. Cover the plants with bubble wrap if a sharp frost is forecast.