We know that during the winter months walnuts can be hurt by either too much or too little water. It’s been a dry fall so far and the deep soil profile in most walnut orchards takes significant rainfall to be recharged. Cutting back on water earlier in the fall slows down the tree's growth and helps harden them off. However, drought conditions during winter can make winter kill worse if we get cold temperatures.
So, how do we best apply water during the winter to alleviate drought? If you have water available, I’d suggest a light 1.5 to 2-inch irrigation that simulates typical rainfall patterns. If we’re still dry in December as you’re reading this then beginning to gradually refill the soil profile with occasional 2-inch irrigations would be a good idea starting about now.
Keep an eye on rainfall forecasts and amounts of rain received in your neighborhood so your irrigation timing doesn’t end up creating a condition where the orchard is too wet. Although unlikely if current conditions persist, saturated soils can kill roots from water logging or can increase the chance of crown or root rots developing. Check soil moisture as the winter progresses to see how deep the soil profile has been re‐wetted so you can make sure you don’t have dry soil in the root zone. The ultimate goal is to make sure the soil reservoir is completely refilled either by rain or winter irrigations by the time your walnut trees begin to wake up next March.