As many of us are dreaming about which plants we want to add to our 2025 landscapes and gardens, one thing we need to keep in mind is our growing zone; especially if you are someone who likes to order flowers or shrubs online. Ordering online can be fun because there are so many (and I mean so many) plants to choose from. But if we are not paying attention to the growing zone for that particular plant, we could just be wasting money.

Now some of you are probably well aware of growing zones, but in 2023 the USDA updated their growing zone determinations. While it’s not hugely different from previous years, this shift can make a difference in which plants you might consider for your landscape.

Up until the revision in 2023, Tulsa was part of group 7a. In group 7a we could expect that our average annual extreme low temperature should be somewhere between 0 and 5 degrees.

The new map that was revised in 2023 now shows Tulsa in growing zone 7b which means that our annual extreme low temperature is now predicted to be between 5 and 10 degrees. While this may seem like a pretty small difference, it’s a pretty big deal for gardeners since it means that some of the plants that are barely in our growing zone will now have a better chance of survival, such as our beloved crapemyrtles.

The way growing zones work is, the lower the number the colder winter temperatures you can expect. For example, growing zones in North Dakota are in the 4s and 3s. In these areas, they can expect an average low extreme temperature of between -30 to -40 degrees. At the same time, areas of Florida are in growing zones 9 and 10 where they can expect average low extremes to be in the 20s to 40s. As you can guess, some plants that are perennial in Florida, likely won’t survive the winter in Oklahoma, and especially not North Dakota. For example: poinsettias can be perennial in zones 9 and 10.

This information is further complicated by this fact; when do we have an average year? Sometimes we get that North Dakota weather down here with lows of minus 15 or such. Temperatures in this range can wreak havoc on our plants. But, knowing this, when a super low temperature is on the way, you might want to bring that plant marginal indoors if you can or perhaps wrap it to help give it a better shot at surviving the winter blast.

How do we as gardeners use this information? It helps us know which plants have a better chance of surviving and thriving in our landscapes, and it helps us know which plants we need to bring indoors during the winter or a particularly rough cold stretch.

So far this year, it hasn’t been too bad, but knowing what we know, there’s always a chance for an outlier storm that might take out some of our favorite plants if we don’t take some precautions. Good luck!

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. Graphic: USDA