How To Harden Off Plants

Tomato seedlings outside being hardened off 2018

Start slowly. Put the plants outside on a partly-cloudy day the first time, with not too much wind.

Make sure they’re well-watered. Leave them out for about 20 minutes the first time, and not at noon (before 11 or after 1 is ideal.) Keep an eye on them, and if they start to get droopy, bring them back in and cut back on the time the next day to 15 minutes, or 10 if need be.

If it’s windy, put them in a cardboard box so they get light but not knocked over.

Gradually every day increase the amount of sunlight by about ten to fifteen minutes. Again, keep an eye on them, don’t let them get sunburned (it will make their leaves turn brown and fall off, so to be avoided!)

Work your way up to about four hours a day, then you can leave them out at night as long as the temps are above 40 degrees.

Once the nighttime temps are above 55 degrees, they’re ready to go in the garden. If you plant them before that they won’t do well. So being patient is worth it.

If you have them in pots for more than two weeks, give them a small amount of fertilizer, at about half the strength showing on the bottle. I like to use fish emulsion; it’s gentle but gives them nitrogen, which they need.

Best of luck!