Why Bald Cypress Trees Turn Brown in Summer

The bald cypress (Taxodium distichum) is one of the rare species of conifers – the term for trees that spread their seeds via cones – that loses its leaves every year, hence its common name. Bald cypress leaves turn an orange-brown color each fall. However, bald cypress tree leaves turning brown in the summer is often a sign of an infestation.

Bald cypress trees grow in a conelike shape. In the wild, a bald cypress tree can soar to heights of up to 125 feet, but in cultivation, this species tends to be somewhere between 50 and 70 feet tall. There are also dwarf cultivars on the market.

The foliage of the bald cypress can be described as feathery. These trees offer good fall color before shedding their leaves. Bald cypress trees have long life spans, as they can survive for several centuries.

The bald cypress is winter hardy in U.S. Department of Agriculture plant hardiness zones 4 to 11. In the southern part of their range, they often grow in swampy areas, where they tend to send up root extensions often referred to as knees. Bald cypress trees are nonetheless capable of adapting to many environments and are tolerant of drier urban conditions.

If a bald cypress tree is turning brown in the summer, it is very likely infested with microscopic arachnids known as bald cypress rust mites, or Epitrimerus taxodii. This species feeds only on bald cypress trees. A single leaf can harbor countless mites, which cannot be seen with the naked eye.

Mites tend to be most active during hot summers when rain is scarce. The feeding of the rust mites, which survive by sucking sap out of the cypress needles, can cause the foliage of a bald cypress to turn brown and drop in late summer.

Treating a mite infestation is not always necessary or practical, however. For example, horticultural oils might kill rust mites, but they can cause serious injury to a bald cypress tree. Chemicals to control mites, called miticides, can also kill beneficial insects that prey on mites and ultimately exacerbate the problem.

Rust mites are not the only pests that can wreak havoc on a bald cypress tree. The caterpillar of a moth known as the bagworm, which gets its name because it forms pouches that hang from tree branches, can sometimes prematurely defoliate large swaths of a cypress tree. Feeding by an insect known as the cypress leaf beetle can also result in leaf discoloration. Trees that are stressed are also vulnerable to twig blight, a fungal disease that results in the death of the tree's branch tips.

Good cultural practices can help keep a bald cypress tree free of pests and diseases and keep its foliage looking its best. It is important for a bald cypress tree to grow in soil that has an acidic pH. If the pH of the soil is too high, the leaves may turn yellow. Bald cypress trees don't usually require pruning, but you should always remove dead or diseased branches.