Texas is separated into five different gardening zones based on the USDA horticultural zone map, because of the chance of frost or continuing high heat through September, which can affect many tender vegetables. However, there are some heat- and cold-tolerant vegetable plants that can be planted in September throughout the state of Texas.
Plant broccoli in September for harvest in 60 days. Broccoli can stand some heat before setting the broccoli flower that is commonly eaten and will tolerate frost. Choose a heat tolerant variety such as Packman if you live in the warmer parts of the state.
Spinach can be planted in September if protected from the hottest sun in the warmer parts of the state such as near Laredo. Once the rosettes are formed, spinach can tolerate a hard freeze or light snow.
Carrot seeds will sprout when the soil temperatures begin to cool in September. Carrots are cold tolerant and will grow and produce carrots into late fall and early winter in most parts of the state.
Collards or collard greens thrive in warm weather and cold. They are a green leafy vegetable that can be used fresh in salads or cooked with pork and spices.
Plant turnip seed in September for green and vegetable production throughout the cooler months.
Mustard is a green with a spicy peppery flavor that tolerates cooler weather when mature and warmer weather when young. Cooler weather prevents common mustard diseases like powdery mildew and amplifies the peppery taste of mustard greens.