Simple but Necessary: Hardening Off Vegetable Seedlings

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Transplanting seedlings into the garden

Photo by Marc Hall

What is hardening off of plants?

When you recommend “hardening off” vegetables to many people, the response can often be a blank stare. Whether you start your own seeds under fluorescent lights or purchase starter plants, though, the hardening off process is really important. Why? Because it helps your plants adjust to the environmental changes they’ll experience when planted in the garden.

Rather than suddenly moving a seedling from home to garden, gradually hardening your plants will reduce the shock they will experience and prepare them for the firmer growth they are getting ready to do. The process is simple, but does require some time and attention on your part for a week or two.

How to Harden Off Your Vegetable Seedlings

  • A week or so prior to moving your seedlings to the garden, set them outside on any warm day. If possible, set them in partial shade where they are protected from the wind. The first couple days, you’ll only want to set them outside for a few hours, but over time, you can increase the amount of time they spend outside, as well as how much sun they receive.
  • Bring your plants back indoors overnight or during colder temps (such as frost warnings). Even cold-hardy plants can suffer damage if exposed to freezing temps before hardening properly.
  • Another aspect of hardening includes cutting back on water and fertilizer. Of course, don’t allow your plants to wilt, but definitely increase the space between waterings so their growth will slow while transitioning.
  • When your plants have spent the majority of their day in the sun and can tolerate less water, they are probably ready for their new home in your prepared garden spot.

If this sounds like a lot of work, consider hardening off your plants in a large rolling container, such as a flat garden cart. This will allow you to pull plants in and out of a basement or garage with very little trouble.