Issue: January 7, 2006
Ok to mulch trees in winter
Question:
We live at an elevation of 4600 feet in the Las Cruces area. Our soil is sandy and dry. In the spring, there is a lot of wind. Last fall we planted many trees such as pi–ons, mesquites, apricots, figs, lead ball trees, palo verdes, a chitalpa, and others.
We watered these trees through the winter to keep their roots moist and have put a few inches of dried leaves under each tree as mulch. That is our concern. Is the mulch a good idea, or will it keep the warmth of the sun from the roots? It also makes it hard to determine when the soil is dry.
Answer:
You are doing the proper thing. It is important to keep the soil moist around the roots of newly planted trees because they have a very limited root system. Applying mulch at the base of each tree helps maintain moisture around the roots.
An established tree often shades its own roots with its lowest branches (and leaves) and mulches itself with fallen leaves. Keeping the warmth of the sun from the roots is not a problem; it is a benefit. The warmth of the sun dries the soil more quickly, and frequent warming and freezing is much more damaging to roots of many trees than constantly cold soil. By helping to maintain constant moisture and temperature, the mulch benefits the roots of the trees in this harsh environment. Once they have established, these trees will modify the environment for you and other plants in the landscape.
The mulch also benefits plants by slowly releasing nutrients into the soil as the leaves decay. This is a natural process in the forest and even in the arid environment in which most of your new trees are native. You have chosen wisely to apply the mulch.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.
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