Now that winter is approaching, I remember the deep freeze of February 2021 and want to do my best to help my plants survive if that happens again this year. Any suggestions? RD

Weather can be surprising, just like our recent mid-October freeze. While we can’t control the weather, there are some things we can do to give our plants the best shot at weathering our unpredictable Oklahoma winters.

The first thing we can do is purchase plants that are rated for our growing zone. The USDA divides the county into growing zones which are determined by average winter freeze temperatures. Tulsa is in growing zone 7a which means that on an average year, we shouldn’t get below 0 degrees. But we all know how we come up with averages - some years are above average, and some years are below average. February 2021 was definitely below average with temperatures sinking to -12 degrees in the Tulsa area. Some places were even colder. This is weather they would expect in Growing Zone 5b so a lot of our Zone 7 rated plants didn’t do well.

As you probably remember, our crapemyrtles didn’t fare well after that deep freeze. This is because crapemyrtles are rated for growing zones 7 - 10 or essentially nothing colder that Zone 7. As a result, a lot of people lost their crapemyrtles and an assortment of other plants.

So should you stop purchasing plants that are rated for warmer climates, not necessarily. But if you do, just know you will likely have to bring them indoors during an uncharacteristically cold period. For example, tropical hibiscus.

Many of us have tropical hibiscus plants (including me) and enjoy them very much. It’s hard to beat those dinner plate sized flowers. But, once it starts to get cooler, I always bring it indoors for the winter. The reason for this is that tropical hibiscus plants are rated for growing zones 9-11. Growing zone 9, on average, doesn’t get below 20 degrees. So, if you do have plants rated for warmer growing zones, hopefully you already have them indoors.

For the rest of your plants that are in the appropriate growing zone, the best thing you can do to help them survive the winter is to keep them healthy and happy during the rest of the growing season. We do this by fertilizing, pruning, mulching, and watering. Plants that are not healthy, easily get stressed during the winter and succumb to the cold. But healthy and thriving plants have a much better chance of survival.

The best time to fertilize your plants is during the growing season from spring till about mid-August. Fertilizing after August can stimulate new growth in your plants and this new growth will be more vulnerable to damage during the winter.

Pruning is another great way to take care of your plants and help them lead healthy lives. This is not the time to prune most plants for the same reason we don’t fertilize now; pruning can stimulate new growth and that new growth doesn’t fair well during the winter. To find out when to prune your plants, we have a fairly extensive pruning guide on our website (tulsamastergardeners.org) under the Lawn and Garden Help section.

One thing we can do to help our plants in the winter is to make sure they get enough water. More often than not, nature does a good job of meeting the water needs of our plants in the winter. However, if we go a few weeks without any rain, sleet, or snow, plan on giving your plants a good soaking about once a month to keep them healthy.

Now some of you are probably saying “just tell me how much water to put down.” While a guideline like that would be useful, the type of soil you have in your landscape makes a big difference in how much and how often you need to water. Soils with a high clay content will retain water better that more porous, sandy soils. So, clay soils will need to be watered more often and for shorter periods of time than sandy soils. If your soil is a compacted, you might need to poke some holes in the ground to provide for better water absorption.

Garden mulch is another thing you can utilize to help you plants through the winter. An insulating layer of mulch helps retain moisture and keeps the soil a little warmer. However, don’t apply mulch in the fall until after we’ve had that first freeze. Mulching too early can confuse the plants into thinking it’s still the growing season which can lead to damage. So, winter mulch goes on after a good freeze.

Mulch can also help the plants during the winter in another way. Invariably, we will get a few warm days in late winter which will make the plants think it is time to start growing. However, a good layer of mulch will keep the soil temperature more constant and help minimize this type of early growth. For trees and woody plants, be sure to keep the mulch away from the trunk of the tree because mulch retains moisture and moist bark is weakened which makes it more susceptible to disease.

If you engage in these practices, your plants will have their best chance for survival. See you in the garden!

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: Oklahoma State University Agricultural Communications Services