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November 1, 2023

Frost Freezes and Hardiness Zones

Frosts, Freezes And Hardiness Zones Affect Your Landscape

This is the time of year when meteorologists warn us of impending frosts and freezes. These are accompanied by warnings to bring plants inside or cover them up. What does it mean for the average homeowner?

For most residential landscapes, no precautions are needed, especially if they’re well established. Plants bought at local garden centers or planted by a landscape professional should be hardy in our area. The United States Department of Agriculture publishes a plant hardiness zone map. This color-coded map shows the average annual minimum winter temperature for every area of the country. Here in the Rochester/Finger Lakes region, we’re in zone 5b (-15 –      -10 degrees Fahrenheit).

Some zone 6a (-10 – -5 degrees F) pockets, known as microclimates, exist here but most garden centers and landscape professionals handle only “durable” plants hardy to zone 5 or colder, especially if they’re guaranteeing them. I define durable plants as trees, shrubs, perennials and turfgrass.

You’ll know your plants are winter hardy if your landscape has survived one or more winters. Don’t use last winter’s mild weather as a guide. If you added new plants over the summer, check the nursery tag that was attached to the plant to be sure it’s a zone 5 plant. If you didn’t save the tag, contact the garden center or landscape contractor and ask them. Or check the internet.

Frost warnings are issued when the overnight temperature is predicted to dip below 36 degrees F. You’ll know we had a frost when you look outside the next morning and see it on the ground. When the temperature reaches 32°F, it’s a freeze. Frost and freeze warnings are issued so you can take appropriate action to protect your plants, especially those that are very tender. The most serious are killing frosts – those that are actual freezes. They are cold enough to kill all but the hardiest plants and signal the end of the growing season.

Take precautions if you planted new plants or threw caution to the wind and bought plants hardy to zone 6 or higher. (Zones begin in the cold north and the numbers get higher as they progress to the warmer south.) Speaking of winds, wrapping any new or tender plant in burlap will protect them from some of the high winds we experience, especially those off the lakes.

The best way to wrap a plant is to install wood poles all the way around the plant and three to six inches away from the plant. They should be at least eight feet tall to discourage deer browsing. Then wrap burlap around the plant, stapling it to the poles. Leave the top open so the plant will have access to sun and moisture.

Frost and freeze warnings apply mostly to annual, vegetable and containerized plants. Unless they’re late season bloomers, annuals will be at the end of their life anyway. If you have a vegetable garden, harvest the produce before it can freeze. Containerized plants should be in their winter home by now. Those that are still in their summer home should be taken inside when the first frost is predicted.

Plants respond to temperature and light. That’s why you should heed frost and freeze warnings and buy only durable plants hardy to zone 5.