Gardeners in the Lone Star State find the topography and climate widely variable across the expansive state. Texas' summers are long and hot, while the winters are cool but mild compared to states farther north. Knowing when to plant in Texas depends on the types of plants grown, as well as seasonal weather patterns, rainfall and the threat of frost. Since Texas is so large and variable, contact your local cooperative extension office for information most pertinent to your county.
When it comes to successfully growing perennials, palms and woody trees or shrubs, knowing the U.S. Department of Agriculture Plant Hardiness Zone designations in Texas helps you select appropriate plants for your garden. The USDA zones rate plants based on their ability to survive average annual minimum winter temperatures. Texas spans USDA zones 6 through 9, almost progressing north-to-south in 150-mile-wide bands. In the northern panhandle, the winters are coldest in zone 6 with temperatures as low as minus 10 degrees F. The southernmost tip is in zone 9 where winter lows drop to around 25 F.
The Growing Season
The growing season is the number of days between the last frost in spring and the first frost in fall. Growing seasons in Texas generally are long, anywhere from 200 to almost 300 days. Tender crops that do not survive frosts are only grown within the growing season, such as corn, tomatoes or summer-blooming annual flowers. The start of the growing season begins as early as late February in southernmost Texas but delayed until late April near Amarillo. The first fall frost occurs around Nov. 1 in the panhandle but not until mid to late January south of Corpus Christi.
Another component is climate, particularly summer heat, winter cold, and amount and timing of precipitation. Western Texas counties are colder in winter, hotter in summer and receive much less rainfall and humidity when compared to the woodlands of East Texas. These nuances affect timing of planting activities or plant hardiness well beyond just the USDA hardiness zones and spring and fall frost dates. Local cooperative extension offices provide precise insight into planting issues, zones and timeframes in the counties across Texas.
Microclimates exist within individual properties. Microclimates are isolated pockets with slight modifications in temperature or moisture. Walk through a property and note where rainfall runoff pools or where soils dry out more quickly in summer. Various spots may be shielded from cold winds or rarely get as cold at night because of their proximity to buildings or if located on a south-facing hillside. Use microclimates to grow plants that prefer different soil types, moisture, or amount of summer warmth or winter cold.