How Often Should You Water New Walnut Trees?

Irrigation Methods

• Common walnut-tree irrigation methods include flood, furrow, border strip, sprinkler and drip. Flood irrigation is common in commercial orchards, but it should be avoided as a means of watering new walnut trees. Young trees lack sufficient foliage to process excessive moisture back into the environment, and the fractured soil profile will absorb more water. Lower-pressure drip irrigation is preferred by young walnut trees, because it continually replaces water in the root zone as it is used.

Adjacency Considerations

• A good, long soaking of the soil is far more effective than frequent, shallow watering of walnut trees. Fortunately, this kind of watering is also favored by many home lawns. It is likely that walnut trees planted within a home lawn will receive adequate irrigation from adjacent grass watering. When watering young walnut trees that are not surrounded by maintained grass, try to avoid excess wetting outside the root zone. Watering beyond the root zone of trees wastes water resources and can encourage competing weed growth. Be aware, weed growth and competition for other plants may seriously limit the amount of irrigation available for walnut trees.

Water Stress Effects

• Water stress is produced by either excessive or insufficient water, or possibly a combination of both at separate times. Water stress reduces vegetative vigor and nut production. It also causes increased vulnerability to insect infestation and fungal infections -- and it may limit the tree's ability to uptake nutrients. Symptoms of water stress vary in degree and intensity, but may include leaf wilt, defoliation, limited shoot growth, crown die-back, root rot and general tree decline.

Soil Type and Irrigation

• Generally, walnut trees prefer deep, fertile, well-drained soil of alluvial origin with a pH between 6 and 7.5. The single most important site selection criterion is good soil drainage. Walnut trees will not tolerate extended periods of standing water. Inadequate oxygen levels from as little as a couple of days of flooding can seriously damage or even kill walnut trees. On the other hand, a lack of sufficient rain or irrigation during the growing season will result in reduced nut quality and quantity. Alternate bearing tendencies may also be exacerbated.