Gardening in Texas: zones, frost dates and when to plant

Five gardening regions, two seasons

Texas A&M AgriLife Extension’s Fall Vegetable Gardening Guide for Texas divides the state into five gardening regions by average winter low. Region I is the coldest, with average minimum temperatures of -10 to 0°F. Region V is the mildest, at 25 to 30°F. Planting dates move a long way between them. The guide’s last good dates for setting out fall tomatoes, peppers and eggplant run from late June in Region I to September 1 in Region V, and fall cabbage and broccoli can go in as late as November in Region V.

AgriLife’s Texas Home Vegetable Gardening Guide (E-502) says Texas gardeners can harvest vegetables year-round. The basic rule is to plant as early as you can in both spring and fall so crops mature in good weather, not in summer heat or winter cold. Use the frost dates for your city above to work out your own planting windows.

What limits Texas gardens

Soil. E-502 describes Texas soils as running from deep sands to fertile, well-drained ground to heavy dark clays sitting on caliche or hardpan. Each needs different care:

• Clay: work in 1 to 2 inches of sand and 2 to 3 inches of organic matter, turned 8 to 10 inches deep. Add gypsum on heavy clay. Expect improvement to take several years.
• Sand: sandy soil needs fertilizer most but burns plants if fed heavily. Give lighter doses more often. Crops on sand also respond to extra potassium, while crops on clay usually do not.
• Alkaline ground: place superphosphate in a band under the seed row before planting.

Never work wet soil. If a squeezed handful stays in a ball and won’t crumble, wait.

Heat and dry spells. E-502 links tomato blossom drop to hot, dry periods. The fix is mulch, steady watering and heat-tolerant varieties. Most gardens need about an inch of rain or irrigation a week, enough to wet the soil at least 6 inches deep, and sandy soils need water more often than heavy dark ones. AgriLife vegetable specialist Joe Masabni advises judging moisture by the soil about 4 inches down, where mature roots are, not by the surface.

Pests. E-502 notes that long growing seasons and mild winters support large insect populations. Masabni puts it more bluntly in an AgriLife Today interview: be ready to fight pests and diseases. In his trials, unsprayed plants produced only about a tenth of their potential crop. Spider mites are a common summer pest on vegetables.

Disease. Drip irrigation keeps water off the leaves. If you use sprinklers, water in the morning so foliage dries before night.

Fall gardens: AgriLife’s approach

Fall is where Texas differs most from northern states, and the fall guide treats it as its own season:

• Use transplants. Fall crops generally do better from transplants than seed, and tomatoes and peppers should always be transplanted. Buy the largest transplants you can find.
• Water through the first weeks. Transplants in small cells need about two weeks to grow out of their root balls and may need water every day in late-summer heat. Soggy soil rots roots, so check moisture by feel first.
• Group crops by frost tolerance. Plant frost-tolerant crops such as broccoli, cabbage, carrots, collards, lettuce, spinach and turnips together. Keep frost-tender beans, squash, tomatoes and peppers in their own block so you can pull them after the first killing frost.
• Prepare the bed. Clear out spring crop residue and keep it out of the compost, since it likely carries insects and disease. Never use poultry manure on a fall garden.
• Time fall tomatoes. AgriLife’s tomato fact sheet suggests transplanting them about 100 days before the first expected frost.

Choosing varieties for your region

AgriLife stresses that only three or four varieties of any vegetable are well suited to a given part of Texas. E-502 advises keeping trials of unproven varieties small. The fall guide’s statewide list includes:

• Onions: short-day ‘Texas 1015’, ‘Granex’ and ‘Early Grano 502’, and long-day ‘Candy’.
• Peppers: ‘TAM Mild Jalapeño’ and ‘TAM Hidalgo Serrano’.
• Southern peas: ‘Texas Pink Eye’, ‘Texas Cream 8’ and ‘Zipper Cream’.
• Sweet potatoes: ‘Beauregard’.
• Broccoli: ‘Green Magic’ and ‘Packman’.

The tomato fact sheet lists ‘Celebrity’, ‘Better Boy’, ‘Big Beef’ and ‘Juliet’ among its choices. For your county, AgriLife’s online Vegetable Variety Selector and your county Extension agent can narrow the list.

Testing the soil

E-502 recommends testing garden soil every 2 to 3 years and asking your county Extension agent for a soil test kit to get fertilizer rates matched to your ground. The same guide notes that the Texas AgriLife Extension Soil Testing Laboratory can test for nematodes. That test is worth getting before you haul in sand or organic matter, which can bring nematodes with it.