Question: What does a “Hardiness Zone” mean when I’m buying plants?
Answer: Plants have certain minimum temperatures below which they simply cannot survive. For tropical hibiscus, for example, it’s 32 degrees F. For rose of Sharon, a type of woody and hardy hibiscus, it’s -10 degrees F. Every plant has its limits. Years ago the United States Department of Agriculture cataloged all of the counties in the United States to determine their average lowest temperature of each winter, then they broke the country into 10 different zones. Four of those zones are represented in Texas. Keep in mind that the larger the zone number, the warmer the winters. The Texas Panhandle is Zone 6 (-10 F to 0), while much of the Trans-Pecos and North Central Texas fall into Zone 7 (0 to +10 F). Central Texas, the Hill Country and Big Bend are mostly in Zone 8 (10 F to 20F), while deep South Texas is in Zone 9 (20 F to 30 F). When you go shopping, you should buy only plants that are winter-hardy to your county’s zone rating or northward. In other words, if you live in Zone 7, you should choose only plants suited to Zones 7, 6, 5, 4 and perhaps 3. Many of those really cold-hardy plants, from Zone 3, as counter-examples, have trouble with our heat, so they may or may not be good for the area.