Spring Planting in Texas

 

by Elmer Krehbiel, Master Gardener
March 5, 2004

The average last freezing temperature in Central Texas is today, March 5. The latest date for the last freeze was April 13.

If the last freeze has occurred, it is safe to start warm-season crops when the soil temperature is suitable for seedlings. Earlier this week, temperatures were in the lower 60s in raised beds. Many gardeners try to start tomato and other plants early to develop an early harvest.

Probably the best protector from cold temperatures (16 to 10 degrees F) for an individual plant is the wall-owater. It has 18 plastic tubes that are 18 inches tall. After the tubes are filled with water, the sun warms the water, which warms the plant and soil. It also protects the plant from the wind.

In Central Texas, a tomato plant usually will grow out the top of a wall-owater in less than a month. I have used them since the late 1980s. A plant with flowers needs to be vibrated often so fruit will set. If a large plant grows out the top, that part of the plant must be covered with other material when cold temperatures are expected. A plant started in a wall-owater should mature about one month earlier than normal.

Black plastic mulch will absorb heat from the sun to warm the soil, and clear-plastic small row covers will allow heat from the sun to warm the plants and soil.

During the recent winter months, the rainfall was much more than normal, creating what could be considered a mud season.

Soil temperature should be measured between 7 to 8 a.m. at a depth of about four inches. If a soil thermometer is not available, a heating/air conditioning pocket one will do.

Wind-chill temperatures do not apply to plants.

Cold-moist soil usually causes seeds to rot and small plants to become permanently stunted. Cold air usually wilts or stunts seedlings.

Soil Temperature for Planting

Each crop has a suitable temperature range of soil and air. Seeds germinate and transplants grow faster when the temperatures are above the minimum.

  • If the soil temperature is 40+ degrees F., greens, garden peas and potatoes can be planted.
  • If the soil temperature is 45+ degrees F, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, kale, lettuce, radish, spinach,  and also bachelors buttons and pansies can be planted.
  • If the soil temperature is 50+ degrees F, beets, onions sets, and Swiss chard can be planted.
  • If the soil temperature is 60+ degrees F, pole beans, sweet corn/heirlooms, tomatoes, turnips, watermelons, also alyssum, cleome, cosmos, dusty Miller, and sunflowers can be planted.
  • If the soil temperature is 65+ degrees F, bush beans, sweet corn/SE hybrids, cucumbers, also ageratum, marigolds, nasturtium, petunias, portulaca, and salvia can be planted.
  • If the soil temperature is 70+ degrees F, lima beans, sweet corn/super-sweet hybrids, okra, southern peas, peppers, sweet potatoes, pumpkins, summer squash, winter squash, also celosia, coleus, impatiens, and periwinkles can be planted.
  • If the soil temperature is 75+ degrees F, cantaloupe, sweet corn/super-sweet hybrids, and eggplant can be planted.

Temperatures for Production

  • If temperatures are below 45 degrees F for the tomato varieties grown in this area, most of the blossoms will drop or deep cracks will form in the fruit from the stem outward (cat-face).
  • If temperatures are below 40 degrees F, tomato plants are usually damaged. During the past years, some gardeners have re-planted several times.

Research indicates that tomato plants should be potted up several times, then set in the garden or containers before the flower buds open or fruit set. I usually pot up tomato and pepper plants to 4 inch and 6 inch pots and one-gallon cans before setting them in the garden or a larger container.

If the temperatures are too low for the beans, they will not develop a normal production.

During years 2000 and 2003, the early spring planting season was too cold and wet to plant sweet corn S.E. hybrid seeds. So, I seeded the crop later, and both crops did not have any insect or worm damage on the ears when harvested.

All of warm-season crops are negatively affected by cold soil and/or cold air.

Dr. Elmer Krehbiel is the former President of Keep Brazos Beautiful. See his column in The Eagle.