Hardening Off Plants
We harden off plants because those that are started indoors are not yet ready to be exposed to wind or sun. Much like humans, plants need to slowly increase the amount of sunshine they’re exposed to or they’ll get burned!
If you don’t harden your plants, the tender plants will get burned by the sun, the shock of cold, or the wind. Some plants may recover from burn (even fully), but their growth will be set back a few weeks while they recover.
How to Harden Plants
The best way to harden plants is to put them outside for a few hours the first day and then bring them in at night. Each day, increase the number of hours they are exposed to sunshine until finally after 3 or 4 days you can leave them out all night.
Partly cloudy days are perfect for hardening plants. If it’s a strong sunny day, set them in the shade, or ideally in part shade, for the first day. Using Reemay cloth, or floating row cover, to shade the plants is a good approach to hardening them on a sunny day.
For a little extra protection
Try this trick! Cut out the bottom of a gallon milk jug and place over your new transplant, burying the bottom of the jug in to the soil an inch or so deep. Remember to remove the jugs when you water the plants, or water each one through the hole on top of the jug.