Use cold frames to extend your growing season

By Linda Dolak

OSU Ext. master gardener volunteer

You don’t have to stop gardening after the first frost. You can easily use a cold frame” to keep producing late into the fall and early winter.

The main difference between a raised garden and a cold frame is that the cold frame acts like a heat source for your plants.

Beds raised 2 feet or more can be used as cold frames because the bed warms quicker than the ground. You will need to cover it with a lightweight clear plastic cover or a discarded window sash when it gets cold to get the heating effect.

It acts like a mini-greenhouse because it captures the heat from the sun. It can keep tender plants producing a month or two past the first frost, or maybe all winter.

If you want a fresh salad for Christmas, a cold frame may allow you to do that.

Root crops, herbs, lettuce, spinach, kale and chard do well in cold frames.

Cold frames are inexpensive and easy to make. You basically build them the same as a raised garden frame, but cover the frame.

If you are going to use the frame only as a cold frame, one of the longer sides should be slightly taller than the front to allow the best warming rays of the sun to reach your delicate starter plants next spring.

As with a raised garden, you also want to pick a sunny spot with protection from the wind. Some gardeners prefer to dig the soil about three inches and tuck the frame into the soil to insulate it.

Be sure you have good drainage, adding some gravel if necessary to improve it. Prepare the soil as you would for the raised garden.

Wait until the weather gets cold to start using it. You will need to open the window about 6 inches if the temperature is above 40 degrees, or totally if it reaches 50 degrees, to allow some of the heat to escape. As the temperature drops, close the lid for the cooler nights. If it gets really cold, throw an old blanket or straw over the top for insulation.

Cold frames can be used throughout the year.

Learn to build your own at go.osu.edu/coldframe.