The globe willow tree (Salix babylonica "Navajo" and Salix matsudana "Navajo") is a drought-tolerant willow cultivar that gets its name from its distinctive globe, or umbrella, shape. Globe willows tolerate a variety of soil and site conditions and can add a dramatic focal point to a home landscape year-round. These trees will thrive as perennials in U.S. Department of Agriculture plant hardiness zones 5 through 10, but site location is important to prevent stress to the tree and to the homeowner.
Globe willow trees grow 3 feet per year, reaching a height and canopy spread up to 70 feet, with a lifespan of 40 to 150 years. The branches and bark are yellow when trees are young, maturing to a smooth olive-green. Some globe willow trees have been known to reach a trunk circumference of 150 inches. Leaves are light green in the spring, darkening to a medium green in the summer and have hints of yellow in the fall. The spring flowers have a bottle-brush shape, with tiny brown capsule fruits that appear in the summer.
Globe willows tolerate a wide variety of soil types, including clay, loam, sand or even poor soils, and aren't too particular about the soil pH. These willows are cold hardy and tolerate full sun to partial shade. Dig a wide hole, breaking through compacted layers, and plant the tree 2 to 4 inches above the surrounding lawn to allow excess water to drain away and prevent root rot. Young willows have tender bark and should be wrapped for the first two winters to avoid sunscald. Mature trees require watering once every 10 to 17 days.
Pests and Diseases
Globe willows are resistant to verticillium wilt but susceptible to insects such as aphids, beetle borers, caterpillars and spider mites, and diseases such as anthracnose, blights, rots, rust and sooty mold. Treatment typically involves an insecticide or fungicide. Among the most serious problems is frothy flux, a slimy, smelly, sappy material that oozes out of tree tissues and can kill young and old trees in just a few years. The only treatment is to remove all damaged, decaying tissue down to the wood.
Globe willows are popular as shade trees and accent trees for lawns and around water features. However, the extensive root system of globe willows can clog plumbing and sewage lines if they are planted too close to buildings. These trees drop leaves and branches when the tree is healthy, which can be messy, and during periods of environmental stress or high winds they may shed an even larger number of branches.