Plants—no matter if they’re flowers or vegetables—must be toughened up or “hardened off” before you plant them in the garden. They’ve been inside (either in a commercial greenhouse or on your window sill) for weeks and they’re quite tender. Just like humans, plants can get sunburned and wind burned. A little care and time devoted to readying your plants for their new outdoor home will really pay off. It takes about 10 days or so to harden plants. By hardening off your plants, you’ll reduce the shock and stress they’ll undergo when planted outside.
On the first day of the hardening process, take your plants outside for a few hours and place them out of direct sun and wind. Each day lengthen the time a little and expose them to more sun and breeze. After a few days, leave them out all day and night—except if there is a chance of frost.
Tropical house plants (the ones you plan to move outside for summer) need to be hardened off too. My favorite day to begin that process is a mild rainy day. The plants respond well to having the dust washed off their leaves at the same time they get a gentle soaking. This is a great time to give them an organic fertilizer amendment. Poke holes into the compact potting soil around their roots for aeration and to allow the fertilizer to mix into their root zone. Worm castings are the very best choice typically. Just be sure to avoid windy days and direct sun for the first 4 or 5 days and you'll be rewarded with healthy vibrant tropical color all summer long.