Trees for Wet Areas
Published 5:30 am Sunday, February 26, 2023
This article wraps up a series about plants for moist or wet sites. I previously discussed evergreen and deciduous shrubs. This one is about trees.
Bald cypress (Taxodium distichum) is an obvious choice for wet sites where a large tree is desired and knees can be tolerated. Louisiana’s official state tree can grow not just in moist sites but where the roots are submerged in water. A lack of oxygen is a major limitation for the roots of most plants growing in wet areas, but bald cypress produces a type of tissue called aerenchyma that helps it move oxygen from aboveground into the roots. Bald cypress can grow to more than 100 feet tall, though 50 to 70 feet is more common. They are highly storm tolerant. Their knees are a downside when planted in landscapes.
Pond cypress (Taxodium ascendens, or T. distichum var. imbricarium) is a close relative of bald cypress. However, its needles are arranged in a way that give the tree a more delicate appearance. The tree has a narrower canopy, and knees reportedly tend to be smaller and more rounded than those of bald cypress.
Another large-growing tree that tolerates poorly drained sites is nuttall oak (Quercus texana, formerly Q. nuttallii). This tree can grow to 100 feet tall, but 40 to 60 feet is more common. Nuttall oak produces a lot of acorns, which is a desirable attribute when planting for wildlife.
While often maligned due to its brittleness and tendency to break during storms, water oak (Quercus nigra) is a rapidly growing tree that tolerates moist sites. It’s one to consider if you have a naturalistic area on a large piece of property.
Black gum (Nyssa sylvatica), or tupelo, grows on moist sites, and the closely related swamp tupelo (Nyssa biflora) grows in swamps. Long tap roots that make transplanting a challenge limit their use in landscapes.
While most trees mentioned in this article are deciduous, American holly (Ilex opaca) stands out as an evergreen that tolerates moist soil conditions, though it isn’t recommended for sites that experience flooding. It can grow to 40 to 50 feet tall.
Another tree that provides greenery in the winter is sweetbay magnolia (Magnolia virginiana). Within the species and across locations, trees vary with respect to the proportion of their leaves they retain in the winter. The more evergreen sweetbay magnolias are sometimes identified as Magnolia virginiana var. australis. Flowers look a bit like southern magnolia flowers but are smaller (2 to 3 inches wide). The tree can reportedly grow to a height of 60 feet but is often smaller. One or multiple trunks can be retained.
If you’d like a deciduous tree in the medium-height range, Drummond or swamp red maple (Acer rubrum var. drummondii) may fit the bill. It’s not a reliably long-lived tree but provides shade and landscape color during its lifetime. Reddish flowers appear in the winter, and fruits (samaras) of similar colors follow. Trees often have red to yellow fall color. Swamp red maple grows to approximately 50 feet tall.
River birch grows rapidly and reaches a similar height as swamp red maple. Like the latter, it isn’t a very long-lived tree but has qualities that may make it worth having. Many people appreciate the peeling bark. River birch is often grown with multiple trunks but can be trained to a single one if desired.
Among smaller trees, parsley hawthorn (Crataegus marshallii) is an option for moist sites. It grows to approximately 20 feet tall. Leaves of parsley hawthorn resemble those of its namesake. It produces white to pink flowers in the spring, followed by red fruits. Many branches have thorns.
When I talk with people about fruit trees, I often emphasize the need for well-drained soil. However, there are a couple of types of fruit trees that do tolerate less-than-ideal drainage. Mayhaws (Crataegus opaca and other Crataegus species) are first on that list. Many of you are likely familiar with the jelly made from its fruit, which is one of Louisiana’s official state jellies. (The other is sugar cane jelly.) Trees grow to approximately 20 feet tall. Like many plants mentioned, mayhaws can grow on well-drained sites, too.
Our native common persimmon (Diospyros virginiana) also tolerates moist sites. Male and female flowers typically occur on separate plants, and both need to be present for fruit production. As those who have tasted an unripe common persimmon know, it must be ripe before being eaten. Trees can grow to approximately 50 feet tall.
Let me know if you have questions.
Dr. Mary Helen Ferguson is an Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at firstname.lastname@example.org or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).