In winter you'll notice that deciduous trees drop their leaves while evergreen trees retain their leaves year-round. Both types of trees continue to have a need for water in the winter months. Deciduous trees continue to grow their roots throughout the winter months and need water to do so. Evergreen trees take up water year-round since they need to maintain their foliage. As long as the ground isn't frozen, you can water trees during the winter in Texas to promote your trees' health.
Check your air temperature and check the soil to see if it's frozen. You should only water when the air temperature is above 40 degrees Fahrenheit and when the soil is not frozen. Frozen soil won't be able to absorb any moisture, and you'll end up creating more ice.
Apply water slowly under the entire drip line of the tree. You want the moisture to penetrate at least 12 inches into the soil. Use 10 gallons of water for each inch of trunk diameter. Check soil with a soil probe to check its moisture level.
Water at a frequency of 1 to 2 times per month. Newly planted trees may need more frequent watering their first year in the ground.