How to Harden Off Your Seedlings and Starts

Basement light set up

Warm days always bring gardeners out with plant starts ready to plant. These starts might be homegrown, or purchased from various sources, but the urge to plant increases every time the sun shines.

To give your plants the best chance, focus on hardening them off before planting. Hardening off means acclimating them to outside conditions instead of immediate planting. Seedlings grown indoors need this step because they're not used to variable temperatures and humidity.

These precious little seedlings have never felt the full strength of the sun's rays, nor the chill of a cool night, because they have been pampered in your home at a consistent temperature. Imagine going to Hawaii in the middle of February from Seattle and just lying out in the sun. There's no doubt you may get burnt to a crisp. Evening temperatures can wilt your starts overnight, so don't let this happen to you. Your six weeks of constant care shall not go to waste if you harden your plants off.

Hardening off often takes up to 10 days (Just to be safe)

Step 1: Make sure your plants are well watered.

Step2: Place them outside in a protect spot, out of the direct sun, for 2-6 hours depending on the temperature.

Step 3: Bring them in at night.

Step 4: Repeat this process for at least three days.

Step 5: Start placing your plants in the sun for several hours a day, then increase the time outside.

Step 6: After about 5 days, leave your plants out all night.

Step 7: After they have been left out all night for 3-4 days, they are ready to plant in the garden.

Note 1: Cool season plants like broccoli, cabbage, and peas, still need to be hardened off if they are started indoors.

 Note 2: Warm season plants can be hardened off and planted outside when nighttime temperatures reach 55 degrees Fahrenheit. Another option is to harden them off and plant them in the garden with protection such as with cloches or garden fabric.

Good luck with all your plant starts!  I can’t wait to see them growing in the garden.

Basil seedlings