Set it out in a sunny area with your new seedlings inside, with the lid off or open wide. Your frame should be 20 inches to 2 feet in height so that you have room for your plants to grow, and also to allow for the right amount of air flow beneath the lid. Whatever your construction skills can accommodate. The top is clear or translucent, often created from an old window or even a piece of plexiglass. It works like a small, simple greenhouse to give your new plants a more protected space while they adjust to life outside.Īfter you’ve hardened your plants in the cold frame, they get planted out in the garden.Ī basic cold frame is simply a 4-sided box with an open bottom. Serious gardeners who need to harden plants regularly will use a cold frame.

While this is fundamentally a very simple process, it can be awkward and time-consuming if you have a large number of plants to deal with.

Keep repeating until your plants are acclimatized and ready to plant. In the evening, bring them back inside for a safe and warm night. Even if you have been growing under lights, having the actual sun beaming down on them can be traumatic. Get your seedlings organized and set up in a tray for portability, and move the lot of them outside for a period of time each day.Ĭhoose your location carefully so that your little plants are getting enough sun without overdoing it. Will want to introduce your young plants to the outside gradually for Whether or not you take advantage of the fan technique, you Just when you are ready to plant outside. Get this set up as soon as your seedlings are sprouted, so Otherwise, add a fan to your seedling space, ideally one that oscillates so that the movement isn’t always coming from the same direction. If your plants happen to be growing near a window that gets regular breezes, you can use that. So even your indoor plants need some movement to grow a sturdy stem, which is necessary to survive outside. Think of how strong a muscle is if you never have to use it. While that may not seem like a problem, it means that the structure of the stem has not had to develop the strength to resist the wind. Having plants do their early growing and development indoors means they only have a quiet atmosphere of still air to deal with.

Hardening off seedlings