At this time of the year, we can start thinking about hardenening off our young seedlings. Depending where you live, the last frosts will be still around until the start of May, but, some seedlings can still be hardened off.

They Key to harden off seedlings for outside planting is to get them gradually used to the difference in temperature.

• Allow at least one week of hardening off. Preferably two weeks.
• Make Use of the Greenhouse, a cold frame or improvised insulation method.
• During the day, especially when sunny make sure the windows are opened to allow sufficient fresh air. Under glass, seedlings can easily get too hot.
• At night simply close the lid to prevent any frost.
• During the hardening off period, feel free to keep the lid open for longer.
• Keep an eye on the temperature. If a particularly frost night is expected, extra insulation such as a blanket may be necessary.
• If seedlings were grown away from the glare of the sun. Make sure they get accustomed to the rays of the sun gradually as well.
• When finally planting out. Choose a day with relatively mild temperatures and not too sunny. This makes for an easier transition.

Notes

Even frost resistant plants like Sweet Peas need hardening off. If they are suddenly moved from inside to outside, the change in temperature can be enough to stunt growth.