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How to Harden Off Plants from the Greenhouse

April 25th, 2013 | Posted by Katie in Greenhouses | Growing Tips - (Comments Off)

How to Harden off Plants

So you’ve spent the spring growing transplants for your garden, and they’re all ready to start growing outside. Now what?

Before you run right out and put them in the garden, you need to harden them off.

What is hardening off?

Hardening off is the process of acclimating plants to the outside when they’re used to being inside. You harden off plants that you’ve grown inside a greenhouse, on a windowsill, or even plants that you’ve picked up from a garden center or plant nursery. It’s more common than ever for people to shop for plants straight from the greenhouse at the garden center. If you pick a plant up from a greenhouse bench and take it home, it needs some time to get used to the outside before it goes in the ground.

Do you harden of plants in the fall?

Any time you are going to take a plant from inside to outside, it’s a good idea to harden it off. If you grow transplants for fall planting, you’ll still want to help them acclimate to the outside. While, in the spring, you’re helping the plants get used to chillier conditions, in the fall, you’re helping them get used to heat and humidity. So, the short answer is, yes, harden off plants in the fall just as you would in the spring.

How to Harden off Plants

Start by decreasing the amount of water you give your plants. Let them dry out a bit between watering.

Next, move plants outdoors into a sheltered location. A porch, patio, or doorway works well for this. You can leave the plants out during the day and then bring them in at night. (Put them in plant flats to make this easier.)

After a few days, you can leave the plants out all night.

You can harden off plants for one to two weeks. Then you’re ready to transplant!

Transplant seedlings on a cloudier day so that they are less stressed from the sun or heat. Keep an eye on transplants. They may need to be watered more often for the first couple of weeks after you plan them in the garden while they’re establishing new root into the surrounding soil.