Found in swamps, floodplains and riparian areas throughout the Deep South, bald cypresses (Taxodium distichum) are some of the most iconic trees in the country.
Often draped with moss and growing straight out of the water to heights in excess of 100 feet, bald cypresses are unmistakable. Bald cypresses play important roles in the habitats in which they grow, and they are an important species that has been used by humans since the dawn of the 20th Century.
Like pines (Pinus spp.), hemlocks (Tsuga spp.) and other cone-bearing trees, bald cypresses are conifers. They bear flat leaflets, arranged in two rows along the branchlets. Unlike most other conifers, bald cypresses are deciduous, meaning that they shed their leaves in the early winter. Before they fall from the trees, the needle-like leaves turn rich red, orange or brown.
Bald cypresses are large trees, and the tallest individuals stand over 140 feet high. However, it takes them quite a while to reach such heights. Fortunately, these long-lived trees are capable of living to very advanced ages – a few living individuals are known to be more than 1,500 years old.
Swamp-dwelling bald cypresses are famous for producing woody structures called “knees”. Knees emerge from the roots, often extending above the water line. Their exact function is not clear, but some hypothesize that they serve as a place for oxygen absorption. When grown in areas without standing water, bald cypresses fail to produce knees.
Habitat and Ecology
Cypress trees form the backbone of most habitats in which they grow, thanks in large part to their ability to grow in flooded habitats. This allows them to form huge forests in areas that would otherwise harbor few trees. These trees not only provide the plants and animals living under their canopies with shelter and protection from the elements, they also produce microclimates that enable countless plant and animal species to live among them.
One of the species that depends heavily on cypresses is Spanish moss (Tillandsia usneoides). Although its common name suggests that it is a moss, it is actually a type of rootless flowering plant called an epiphyte. Although Spanish moss can grow on a variety of tree species, it appears to favor bald cypresses, pond cypresses and live oaks (Quercus virginiana).
The Spanish moss growing on these trees actually forms a microhabitat of its own. The plant’s leaves serve as roosting sites for a number of bats and birds, as well as hunting grounds for insectivorous lizards and frogs. In fact, the moss serves as the only known habitat for Pelegrina tillandsia – a tiny jumping spider.
Waterfowl and rodents, particularly squirrels, eat and spread cypress seeds, but the trees also spread their seeds via water. They float downstream, often ending up on a sandbar or shoreline. Once there, the seeds germinate they grow quickly, in order to avoid drowning in upcoming floods. In ideal places, the young trees may grow more than 2 feet in their first year.
Although they are perhaps the most well-known members of the group, bald cypresses are but one representative of the genus Taxodium. The pond cypress (Taxodium ascendens) inhabits nearly the same range as the bald cypress, yet it is associated with slightly different habitats. Being very similar in morphology to bald cypresses, pond cypresses are treated as a variety of the bald cypress by some authorities.
Pond cypresses may produce knees, as their more familiar relatives do, but they do not produce as many, nor do they reach the size of those produced by bald cypresses. Pond cypresses often bear ascending branch tips (hence their specific name), and they bear awl-shaped leaves, which are held flat against the twig.
The third and final member of the genus is the Montezuma cypress (Taxodium mucronatum). Found in extreme southern Texas and throughout much of Mexico, the Montezuma cypress often produces very large trunks. In fact, the living tree with the greatest documented diameter is a member of this species. The record-holder – called Arbor del Tule by locals — has a diameter of over 37 feet. Unlike its relatives, the Montezuma cypress rarely produces knees and often acclimates well to highland locations.
Like the pond cypress, the Montezuma cypress is considered a variety of the bald cypress by some authorities.
Despite the fact that they are highly specialized trees of southern swamps, bald cypresses often thrive in a variety of locations. They are rated for hardiness zones 4 through 10, and – despite their ability to grow in standing water – often adapt well to arid locations (they do require abundant water during their establishment period). Obviously, bald cypresses are supremely well adapted to areas that experience occasional flooding.
Bald cypresses grow to respectable sizes over human time scales; large specimens reach 75 feet in height, with full, 30-foot-wide canopies. The combination of their beautiful fall foliage and picturesque winter form help to make bald cypresses visually interesting components of backyards, parks and commercial areas.