How to Harden Off Plants

If you’ve grown plants from seeds or cuttings indoors, or have purchased tender young specimens from the covered area of…

Hardening Plants

To harden off plants you simply need to introduce them to their new environment in a gradual process. This will slow down their growth and steadily toughen them up, getting them used to being removed from their indoor comforts, where they’ve become accustomed to constant temperatures and aren’t battered by the wind and rain. Hardened-off plants not only have more strength to survive these conditions, but they’ll also be less appealing to snails and other pests who often go for the most tender plants first.

How Long Does it Take Plants to Harden Off?

For the best results opt for a three-week schedule, making sure you time it so that planting out happens when all danger of frosts has passed. To give you an idea of how to gradually increase your plants’ exposure to being outside, here’s a week-by-week overview to harden off plants.

Week-by-week Overview for Hardening Plants

Week 1

For the first week you should aim to expose plants to somewhere a little cooler than they’ve been used to during the day, bringing them back inside later in the afternoon when temperatures start to drop. Plants that have been enjoying the warmth of the house or a heated greenhouse can be transferred to an unheated greenhouse or cold frame during these hours. If you don’t have such covered areas, then you can use horticultural fleece or bubble wrap instead to give plants that extra protection. It’s also worth bearing in mind that it’ll be warmer by the walls of your house than in the middle of the garden.

Week 2

Now they’ve got a taste for what’s to come, you can gradually expose them to more of your local weather conditions. Do this by opening the doors and windows of your greenhouse, raising the lid of your cold frame, or steadily removing layers of fleece and bubble wrap during the day. Continue to bring plants back inside at night.

Week 3

In the third week you can start leaving your plants outside for longer, eventually keeping them out all night. For the first few days give them a little bit more protection at night by moving them to the cold frame or wrapping with fleece until, by the end of the third week, they should be ready for a few days and nights all on their own with no protection. You can still wrap them up if a particularly cold snap comes in though. After a few nights out then they’re ready to plant out full time, hardened off and in the best possible shape to survive whatever weather comes their way.

Do you harden off your plants? What tips do you have? Make sure to share them in the comments!