I am wondering if the flowers in my garden will survive the deep-freeze we just endured. Should my perennials survive or am I looking at having to replace a lot of plants. PF

Oftentimes the term perennial can be confusing so let’s talk a bit about plant classifications and growing zones.

When we go shopping for flowers, we tend to find them grouped into two categories: annuals and perennials. But annuals can be perennials and perennials can be annuals - depending on their growing zone rating. Confused yet?

Here’s the deal. The United States is divided into growing zones. Each zone is given a reference number. Tulsa County is kind of a 6b to maybe a 7a. I say kind of because each year is different, and some years are more different than others. The further south you go, the numbers increase.

These numbers are reference numbers to identify cold hardiness zones. For example, if you had purchased a perennial that was rated for a cold hardiness zone of 7a (which is what we would normally do), this means that your plant is rated to withstand winter temperatures down to -5 degrees. Well, that went out the window last week.

Some perennials are classified as tender perennials for our zone. This means that they are perennial as long as we don’t go below our zone rating for very long.

We also might have plants in our landscape that were originally rated for Zone 8. Zone 8 plants should be perennial down to about 10 to 15 degrees. In a lot of Tulsa winters, they would be just fine. But again, last week kind of blew that out of the water.

These ratings are why a lot of gardeners have plants in pots that come inside in the winter. For example, many of us enjoy tropical hibiscus at home. There’s not much better for a floral landscape than those large hibiscus flowers. But tropical hibiscus is rated for a growing zone of 9-11. This means that they won’t survive in temperatures below freezing. And that is why we bring them in each fall, baby them all winter, and they live to bloom another day.

There is another factor at play we call a microclimate. Microclimates are areas that can consistently remain warmer or cooler than the rest of the yard. A lot of factors can contribute to this such as the slope of the land, the exposure to sun, the protection from the wind, and surrounding shrubbery. All of these influence survival factors for your plants.

So, the bottom line is that you should always check the growing zone rating for your plant before bringing them home to your landscape. Doing so can help you enjoy them for years to come. But in years like this one, most of the “normal” things have gone out the window. Ultimately, we will just have to wait until spring to know how much of our gardens survived.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org.

Photo:  OSU Agricultural Communications Services