Gardening Tips and Highlights Waushara County Master Gardeners

Understanding frosts,

freezes, and hard freezes   

by Christine Yesko          

For northern gardeners, understanding the differences between frosts, freezes, and hard freezes and what you should do to keep your garden growing is important. Here’s the break down on what each term means:

Frost is a light coating of ice formed on solid surfaces, such as leaves, blooms, and blades of grass. As the air gets cooler, water droplets in the air condense on surfaces and freeze. Frost warnings are typically issued when the overnight low is expected to drop to 36 or lower for several hours. Now, you may be thinking, how can the water freeze if the air temperature is above freezing? The answer is that while the official air temperature is above freezing, those readings are taken six-feet above the ground. Temperatures are lower near the ground and lower still in low-lying areas of your yard and garden. That’s why frost tends to form in lower areas of the yard quicker and for a longer time.

Freezes are when the air temperatures sink to between 28 and 32 degrees and stay there for a four or more hours. For many summer season plants (tomatoes, petunias, etc.), this will mark the end of the growing season unless they are covered and kept warm. Get out all the blankets to cover anything that is not frost-hardy that you want to have continue to grow (or at least look good). Some vegetables, such as Brussels sprouts, kale, and parsnips actually taste sweeter after a freeze. Things like peppers and tomatoes that have not been picked should be. You can ripen tomatoes on the counter.

Although we already had our first frost, we are waiting for the hard freezes yet to come. So, we still have time to plant spring-blooming bulbs and do some general clean-up of our gardens. It won’t be long when the harsh winds of the north blow-in and freeze the soil, but until then stay warm.