Rockwall County Master Gardeners

Hardiness Zones

Cold Hardiness

As a gardener, it is important to know your “zone”.  In 2023, USDA made some revisions in the Hardiness Zone Map for the United States. This zone designation refers to the average annual extreme minimum temperature (1991 to 2020) of 10 degrees to fifteen degrees.  In other words, the zone refers to how cold hardy plants will be when growing in our North Central Texas area. In Texas, the Heat Zone designation is also important, shown below. Below is our section of Texas which shows that Rockwall County is in Zone 8b.
Follow this link to the USDA site.

Heat Zone

The American Horticulture Society developed a map to show the different heat zones and ranges of high temperatures. This map is certainly relevant to Texas gardeners. Often, our plant selections that thrive in April  just can’t take the heat of July and August. For Rockwall County, we are in Heat Zone 8. Here is the map of the East portion of Texas – notice how Tarrant and Dallas Counties are zoned higher than our area. Too much concrete?  With the effects of climate change it could be worth while to keep an eye on which zone Rockwall County stays in the future.

American Horticulture Society Heat Zone Map

Will we have another super hot summer? Here is some info about how heat effects your garden. Heat Stress and Photosynthesis in Plants