Our region’s only deciduous conifer
by Steve Carroll, Contributing Columnist
Bald cypress is the longest-lived tree in the eastern U.S.
Bald cypress is a truly unusual tree. It’s a conifer — therefore related to pines and spruces — but it drops all its leaves each fall. It epitomizes the swamps of the southeast U.S., yet it readily grows as far north as New England. It prefers rich, moist-to-wet, acidic soil, yet can be grown as a lawn or street tree in dry, well-drained soil. This is a remarkable native deserving our admiration!
Under favorable conditions, bald cypress (Taxodium distichum) can grow 70-to-100 feet tall or more with a 3-to-5-foot diameter. It is also the longest-lived tree in the eastern U.S.; many specimens surpass 1,000 years old, with at least one North Carolina tree exceeding 2,600 years.
Bald cypress’s soft, at needles are one-half to three-quarters inches long and grow in two ranks along small branches. Leaves become darker green through summer, then contribute to our fall display by turning an attractive rusty red-brown. In winter — when trees are “bald” — the fibrous, reddish-brown bark is evident.
Autumn-leaf drops by conifers occurs in relatively few species, including larches and dawn redwood. This begs the question “Why?” Losing leaves in the fall requires their total replacement the following spring, an immense energy investment. On the other hand, shedding leaves frees trees from maintaining them through the winter. Being leaf- free also decreases water loss through transpiration. Other biochemical and physiological factors affect this “decision,” but in most conifers, the balance has tipped toward retaining leaves. Fortunately, we have these fascinating exceptions that enrich our world.
Like most conifers, bald cypress produces male and female cones on the same tree. Male pollen-bearing cones are small and short-lived, falling off after the dispersal of their pollen by wind. Fertilized female cones are green, globular and up to an inch in diameter; these turn purple-brown before releasing seeds in the fall.
One of this tree’s most unusual features is the development of “knees” that grow upward from its roots, especially in wet soil. At least two hypotheses attempt to explain these. One argues that they contribute to gas exchange, since water and wet soil hold less oxygen than the atmosphere. Another suggests that knees provide additional structural support in water and wet soil.
I was fortunate to have a good-sized tree in the front yard of a previous home. In this full-sun setting the tree produced just a single, small knee, easily kept in check by the lawnmower. But like most trees, bald cypress roots extend well beyond the reach of its canopy. As a result, several knees emerged in the dark, moist confines of our house’s dirt crawl space, requiring me to navigate through this mini-maze when it was necessary to go down there — which I don’t mind admitting was as infrequently as I could get away with!
Bald cypress produces strong, light, rot-resistant wood that has been used to make barrels, railroad ties, shingles, greenhouse benches and other products where rotting might be a problem. It also helps feed our wildlife, with its seeds consumed by turkeys, evening grosbeaks, waterfowl, squirrels, and other birds and mammals.
Bald cypress is a tall, long-lived tree with four-season interest. It’s not suitable for all properties, but if you have the right spot, consider planting this unique and beautiful tree.
Steve Carroll is a botanist and ecologist who speaks and writes about trees, gardening and the world of plants. He is the co-author of “Ecology for Gardeners,” published by Timber Press.