The horse chestnut tree got its name from the habit of some Europeans of using the seeds of the tree to create medicines to treat sick horses. The species is not a native tree in the United States, but after its introduction, it escaped cultivation and it grows wild in parts of the Northeast and the Midwest. The leaves of the horse chestnut are very large and showy, but unfortunately, they are subject to multiple ailments.
The horse chestnut leaf is a palmately compound leaf. This means that individual leaflets occur on the end of a central stem. The separate leaflets fan out in the shape of fingers on a hand, with some larger than others. The leaflets appear fused together at their bases to the top portion of the stem, notes the Ohio Department of Natural Resources website.
Horse chestnut leaves grow on a leafstalk that ranges between 3 inches and 7 inches long. These stalks will develop opposite each other at the nodes on the tree's limbs. To this stem, the leaflets attach, with a variation in their sizes. The smaller leaflets are about 4 inches long, while the biggest leaflets are in the range of 10-inches long. The leaflets have widths between 1.5 inches and 3.5 inches, according to the "National Audubon Society Field Guide to Trees." Usually a horse chestnut leaf has seven individual leaflets, but in some instances, there may only be five.
Botanists use the term "obovate" when describing leaflets and leaf shapes such as those the horse chestnut possesses. Obovate means that the leaflet is at its widest point near the end of the leaf opposite the base. This apex area on a horse chestnut leaf features a blunted tip. The edges of the horse chestnut leaflets have small projections along them, giving them a saw-toothed look.
In the spring, the leaves of the horse chestnut tree are a dull shade of green on the upper surfaces. This shade is much duller on the undersides of the leaves. The tree is not one of those that produce a spectacular display of autumn colors. In the fall, the leaves change to brown, with the more colorful ones being a drab yellowish tint.
Many times, the leaves of the horse chestnut do not make it through the summer unscathed by disease. The tree is at the mercy of a variety of leaf ailments that can turn its entire canopy brown. Some of these include leaf scorch, which is an unavoidable consequence of planting the tree in the full sun, which enhances the production of its flowers and fruit. The leaves will turn brownish and wilt, but this can be somewhat averted by watering the tree routinely through the hot months. Other diseases that affect the horse chestnut foliage include powdery mildew and leaf blotch, with the latter likely to occur year after year, reports the University of Connecticut Plant Database site.