Does a Eucalyptus Tree Turn Brown in the Winter?

Tricky to Identify

• Because there are more than 600 species of eucalyptus and they hybridize freely, they are not always easy to identify. They do, however, share some common characteristics. Eucalyptus may be either trees or shrubs, typically erect, usually with a strong, slender branch formation. Their U.S. Department of Agriculture plant hardiness zones also depend on species. The silver-dollar eucalyptus (Eucalyptus perriniana), for instance, is hardy in USDA zones 8 through 10, while the argyle-apple (Eucalyptus cinerea) grows best in USDA zones 8 through 11. Eucalyptus varies widely in size by species: silver-dollar eucalyptus is 20 to 30 feet in height, while argyle-apple is only 6 to 10 feet.

Leaf Color Matters

• Eucalyptus leaves range in color, but are usually grayish green to grayish blue. Some can take on a blue cast, while others tend toward dark green. Leaves are thick, leathery and heavily scented with the traditionally strong eucalyptus smell. Depending on the type of species, they either grow thickly or may grow in a thinner, more dappled pattern. Knowing the typical growth pattern of your eucalyptus will help you identify whether it’s losing too many leaves.

Brown Leaf Causes

• If you are noticing a steep decline in the number of leaves and a rapid overall browning of leaf color, there could be several causes. Dehydration, which can lead to leaf scorching, is one of them. Although most people associate dehydration with summer heat, it can be just as damaging during the dry winter months, when colder temperatures and lack of water in the leaves can cause them to wither and fall off. Other causes year-round include root rot and canker, which can cause leaves to turn brown and fall off, or leaf spot, which results in blotchy leaf browning and eventual leaf drop if the problem is severe enough.

Responding to Disease

• There is no way to combat root rot except to avoid overwatering and not planting in an area known to have harbored it in past. Slow down your watering schedule if you see possible signs of it, which include dying branches and mushrooms at the base of the tree. Respond to canker by pruning out all infected branches, and removing the tree once the trunk shows signs of the pathogen. Although chemicals are usually unnecessary, you can combat leaf spot by removing fallen leaves and branches to reduce the chance of spreading infection further.

Prevention

• To prevent leaves from becoming brown and scorched, water deeply and thoroughly but infrequently until eucalyptus become established. After that, water during very hot summer months and long periods of drought in the wintertime. Another safety precaution is disinfecting your pruning equipment; reducing transmission of disease by swabbing shears with rubbing alcohol will lessen the chances of leaf browning and drop.