Hardening Off Seedlings

When you start growing a lot of plants, you begin to start seedlings indoors just because you need the space or because you are trying to get a head start on the season. However, sometimes you may find that once you put those seedlings from the kitchen outside, they toast in the sun. Here are a few pointers to prevent this from happening. 

If you get serious, you can build a setup like this one.

  1. When you grow inside, use as much sun/light as possible. You may invest in grow lights to supplement the light, especially those that provide a good spectrum like lighting systems that use metal halide or pressure sodium bulbs. I will address lighting systems for indoors in more detail in a future article.
  2. Grow seedlings until they are sturdy and well-rooted. If they are barely sprouted, you may as well start them outdoors. The point of starting seedlings indoors is to get a head of the season or ahead of the space you are working with.

    Using Russian kale as a parent plant for eggplant seedling.

  3. Gradually expose seedlings to more sun and exposure as you approach planting date. Sun, wind and dryness are the factors that make it difficult for seedlings that have been grown in protected sites indoors. When you gradually expose them, you are helping them build up resources they will need to deal with those elements.
  4. When you finally plant your seedlings, use “parent plants” to protect. These can be previous crops that are on their way out. For example if you are planting new squash seedlings, set them underneath bolting winter greens which will shade them, and hide them from birds.

    You can use a piece of shade cloth or burlap to ease plants into the sun.

  5. You can also use bits of shade cloth to cover individual seedlings for the first few days your seedlings are out of doors. Contemplate building a small structure you can pop over the top of any new plant. This can be used to protect seedlings from sun, or late frosts.
  6. Keep well-watered. Seedlings will be much hardier once they have acclimated to their location, but some extra moisture will help greatly.

A cold frame helps you get ahead of the warm season by protecting seedlings from frost while still providing lots of sun.

It usually only takes a few days to a week before seedlings become acclimated to their new locations. Look for new growth that has developed in the native elements before taking away protections. If you have used parent planting, your seedlings will grow their way out of protection.

If you get serious, you can build a greenhouse that is heated in winter, cooled in summer.

Consider building a cold frame or even a small greenhouse that can help you get a start on the season. A cold frame is primarily used to start seedlings while protecting from the cold but doesn’t protect well from the heat when trying to ahead of the cool season. Though an expensive investment, a heated/cooled greenhouse can be amazing for getting ahead of every season.


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