Soggy Bottoms

Andrew Bunting

Many gardeners struggle with wet or poorly drained soil, either due to the type of soil, soil compaction, a high-water table or proximity to a body of water such as a stream, river, lake or pond. While many plants are intolerant of these conditions, thankfully there are many several that not only tolerate these conditions, but can thrive.

Many varieties of trees can grow in soils that are constantly moist or even waterlogged. One of the best trees for wet areas is the native red maple, Acer rubrum. Over the years there have been many outstanding cultivar selections, including Redpointe, which is a relatively new introduction. It has an upright, broadly pyramidal habit, and like all selections of red maple, has outstanding brilliant red fall color. Because of its outstanding ornamental attributes, it was awarded the Gold Medal Award distinction by the Pennsylvania Horticultural Society. Both Red Sunset and October Glory also have urban tolerance and are great as street trees.

Large photo: Betula nigra Heritage.

Inset photo: Ilex verticillata Winter Gold.

Aptly named the river birch, Betula nigra is found in its natural habitats growing along the flood plain of streams and rivers. The river birch is one of the fastest growing trees. In its youth it has beautiful flaking bark with color tones of cream, pink and brown. Heritage is an outstanding selection for more northern climates. Northern Tribute has superior cold hardiness thriving in Zone 3 and Dura Heat was selected for exceptional heat tolerance.

The hornbeam, or the musclewood, is a native tree that’s been promoted in recent years for its urban toughness and tolerance of many conditions and soil types. Carpinus caroliniana has silver sinuous trunks that become more ornamental with time. The fall color can vary from yellow to red. Firespire is an upright selection reaching 20-ft. tall with a spread of 10 ft. and exceptional red fall color. Because of their size, the hornbeams are often used as street trees under power lines.

Growing in the swamps of the Southern United States, the bald cypress is one of the best trees for extremely saturated soils. Additionally, Taxodium distichum is a deciduous conifer with very fine needles that turn a brilliant coppery orange before they’re shed in the fall. Reaching nearly 100-ft. tall, the habit is fairly upright before it begins to broaden with age. Shawnee Brave is an excellent upright oval selection. Lindsey’s Skyward is more diminutive in stature, reaching only 25-ft. tall at maturity, with a more pyramidal habit. Closely related is the pond cypress, Taxodium ascendens.

Debonair is a selection of the Morris Arboretum, with a broad oval habit and vibrant coppery-orange fall color. And other related species include the Chinese counterpart, the dawn redwood, Metasequoia glyptostroboides. Like the bald cypress and pond cypress, the dawn redwood is a deciduous conifer with bronze fall color and is very fast growing. In its youth it can grow up to 6 ft. a year and quickly matures into a tree with a broadly pyramidal habit. Soul Fire is a new selection with great golden-yellow needles throughout the summer. Some other cultivars come out yellow, but fade to green by mid-summer.

While almost all magnolias like well-drained soil, there’s an exception. The sweetbay magnolia (Magnolia virginiana var. australis) can thrive in wet areas along the coastal plain from Massachusetts south to Florida and east to Louisiana. This tree can be grown as a single-trunked tree or it’s often sold as clump-forming with multiple trunks. At maturity, it will reach 30- to 40-ft. tall with dark green oval leaves and a silvery underside that’s revealed when the wind blows. In mid-spring, star-like flowers emerge that have an amazing lemony fragrance. Flowering will continue sporadically into the late summer. There are several exceptional selections, including Santa Rosa, Satellite, Henry Hicks and Green Shadow.

There are myriad shrubs that will also grow in damp and poorly drained soils. The winterberry hollies (Ilex verticillata) are often found growing along the edge of ponds and lakes in their native habitats. Like other hollies, they’re dioecious, which means there are male and female plants, therefore good fruiting occurs. There needs to be a male pollinator, such as Southern Gentleman, planted in proximity to the female cultivars. Some of the best red fruiting selections include Winter Red and Maryland Beauty. These multi-stemmed shrubs differ from other hollies in that they’re deciduous. As the plump berries mature in fall, the leaves are shed, revealing branches that are heavily laden with fruits. Winter Gold has soft salmon-orange fruits. Cut branches of the winterberry holly are excellent for winter décor.

Far left: Ilex verticillata Winter Red.

Iris versicolor Purple Flame.
Photo courtesy of Mt. Cuba Center.

The native summersweet (Clethra alnifolia) is a spreading shrub that has white or pink bottlebrush-like flower clusters that are sweetly fragrant in August. In the fall, the narrow leaves turn bright yellow. Ruby Spice has soft pink flowers. Sugarina and Hummingbird are more diminutive selections.

Another native shrub that will tolerate very wet conditions, including standing water, is the buttonbush (Cephalanthus occidentalis). In the summer, it’s covered in round, orb-like flower clusters. Fiber Optics is a selection that’s more compact, reaching 6-ft. tall with equal spread. The flowers attract butterflies, especially the swallowtails.

Many types of perennials can also tolerate wet conditions. Native ferns such as ostrich fern (Matteuccia struthiopteris); royal ferns (Osmunda regalis) and cinnamon fern (Osmunda cinnamomea) can tolerate moist areas and are often found in swampy conditions in their native settings. They’re all spreading ferns and can quickly colonize in the garden. A new introduction from the Mt. Cuba Center in Delaware is Iris versicolor Purple Flame, which is characterized by stunning newly emerging purple leaves and blue flowers. Growing in wet areas, this native iris combines well with the swamp milkweed (Asclepias incarnata) and the cardinal flower (Lobelia cardinalis), a magnet for the Ruby-throated Hummingbird.

Regardless of the root cause of your poorly drained or wet soil, the trees, shrubs and perennials mentioned in this article not only thrive in wet conditions, but add great ornament to the environment. GP

Andrew Bunting is the Vice President of Horticulture for the Pennsylvania Horticultural Society (PHS), which uses horticulture to advance the health and well-being of the Greater Philadelphia region. To learn more about PHS, or to become a member and support greening initiatives in over 250 neighborhoods, visit PHSonline.org.