Houston’s subtropical climate allows for a growing season that stretches nearly year-round. Planting schedules are not primarily determined by the last frost date, but rather by the intense heat and humidity of the approaching summer. Gardeners must time their planting to allow crops to mature before temperatures become too high, which is a far greater limitation than the mild, short winter. A successful Houston garden relies on precise timing to avoid the summer’s unproductive period and maximize the output of the two distinct growing seasons.
Understanding Houston’s Unique Growing Environment
Houston falls within the USDA Hardiness Zone 9a and 9b, which indicates a mild winter where the average minimum temperature rarely drops below 20°F to 25°F. The average last spring frost in the area is notably early, typically occurring between late January and mid-February. Conversely, the first frost of autumn is often delayed until late November or early December, resulting in a very long growing window of over 290 days. The sustained summer heat, where temperatures consistently exceeding 90°F cause many common vegetables like tomatoes to stop setting fruit, is the primary limitation. This forces the focus to shift from simply avoiding cold to strategically timing harvests around the summer’s intense heat.
Timing for Cool-Season Vegetables
Cool-season vegetables thrive in temperatures below 75°F. The primary planting opportunity begins in late summer, with the goal of a fall and winter harvest. Gardeners should start seeds for crops like broccoli, cabbage, and kale indoors in early August, preparing them for transplanting into the garden beds by mid-September to early October. For root crops such as carrots, beets, and radishes, direct seeding should begin in mid-October and continue through November.
A spring harvest window opens up in the new year, targeting maturity before the summer heat arrives. Direct sowings of leaf lettuce, spinach, and Swiss chard should occur in January or early February. English peas can also be planted between October and the first week of January, as they are moderately tolerant of the occasional light frost. Planting these crops early in the calendar year ensures they reach maturity by late March or early April, before the rising temperatures cause them to “bolt,” or prematurely flower.
Timing for Warm-Season Vegetables
Warm-season vegetables require consistently warm soil and air temperatures. The main planting period for these heat-loving crops runs from March through May. For long-maturing plants like tomatoes, peppers, and eggplants, seeds should be started indoors in January to give them a six to eight-week head start before transplanting. These transplants are then ready to be moved outdoors into the garden beds in late February to early March.
Direct seeding of quick-growing, warm-season crops like bush beans, cucumbers, and corn can begin in March. Squash and melons are generally planted throughout April and into early May to maximize their productivity before the peak summer heat. It is important to select varieties of tomatoes that are known to be “heat-set,” meaning they can still produce fruit even when daytime temperatures exceed 90°F. The highest-yielding warm-season crops for the intense Houston summer are often okra and Southern peas, and can be planted from April through June.
Planning for Continuous Harvest
Maximizing the garden’s output in Houston’s long season requires a strategy known as succession planting, which involves continuous, staggered planting. Instead of planting an entire row of a quick-maturing crop like radishes or bush beans all at once, new seeds should be sown every two to three weeks. This ensures a steady, manageable supply of produce. This technique is especially useful for greens and root vegetables during the cool season.
Gardeners can also plan for a “second fall garden” by starting cool-season seeds indoors in August, while the summer is still at its peak. These seedlings can then be immediately transplanted into the garden beds as soon as the worst of the summer heat breaks in September. Selecting crops like okra and Malabar spinach, which continue to produce through the high summer temperatures, helps keep the garden productive during the months when other popular vegetables are taking a heat-induced break.