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Ask a Master Gardener: Selecting Plants for Soggy Sites

Updated: Sep 15, 2023

By Dr. Judy Stout, Mobile County Master Gardener, www.mobilecountymastergardeners.org

Master Gardeners often receive requests for assistance in plant selections for problem sites. The types of “problems” vary but, in coastal Alabama, a common issue is too much moisture, or even wet soils. The setting may be adjacent to open waters (the Bay, rivers, and streams, or ponds and lakes); experience seasonal or periodic flooding from heavy rainfalls; be low elevation in the landscape; have a shallow groundwater table; or have underground wet-weather springs. Any of the preceding combined with soils that drain poorly make the problem more difficult. Plantings in these conditions may fail or produce poor plant health or appearance.

Why? Just like us, plants require sufficient oxygen to metabolize their food and maintain healthy tissues. This goes for aboveground parts as well as the roots. When the open spaces in the soil are filled with water and little or no oxygen, roots can slowly die and rot causing the plant to die. Some oxygen is produced during photosynthesis and can be transported to the roots. In addition, plants adapted to wet conditions can store reservoirs of oxygen in large cells (aerenchyma), keeping the roots healthy. Specialized structures, such as cypress knees, place living tissue above the wet area and help with oxygen acquisition.

On a very small site, solutions may include adding sand or grit to the soils to improve drainage. Surface elevations can be increased to reduce or eliminate flooding. Depressions can be filled. However, if the moisture is from below ground, roots of mature plants may still reach unfavorable conditions. Surface water can be redirected with designed and landscaped channels. On a larger scale, these solutions may work but may require some engineering design and can be expensive.

So, what do we do in wet south Alabama? Plant developers have bred cultivars of natives and other plants that are well-adapted to wetter sites and great looking in the home landscape. Trees and larger shrubs are an extra bonus removing excess water from these sites. Let’s work with what we have and select plants that do well in such settings!

Below are some suggestions. Inquire at local, independent nurseries, and shop the various local plant sales, such as those at the Mobile Botanical Gardens (MBG). Many listed are available at either the fall or spring MBG sales. [The MBG fall plant sale is Oct 26, 27, 28 from 9 am to 3 pm.] Save this article as a guide. (* denotes evergreen plants)

TREES. *Slash Pine, Pinus elliotti; *Longleaf Pine, P. palustris; *Bald Cypress, Taxodiumdistichum; *Pond Cypress, T. ascendens; *River Birch, Betula nigra; Paw Paw, Asimina triloba; *Southern Magnolia, Magnolia grandiflora; *Sweet Bay Magnolia, M. virginiana; Black Gum, Nyssa sylvatica; Sweet Gum, Liquidambar styraciflua; *American Holly, Ilex americana; *Yaupon, Ilex vomitoria; *Wax Myrtle, Myrica cerifera; Oaks – Overcup oak, Quercus lyrata; Swamp Chestnut Oak, Q. Michauxii; Cherry Bark Oak, Q. falcata var. pagodifolia; Elderberry, Sambucus canadensis; *Loblolly Bay, Gordonia lasianthus.

SHRUBS. Winterberry, Ilex verticillata; Inkberry, I. glabra; *Fetterbush Lyonia lucida; Buttonbush, Cephalanthus occidentalis; Arrowwood, Viburnum dentatum; Chokeberry, Aronia melanocarpa; Hardy *Anise, Illicium parviflorum; *Florida Anise, I. floridanum; *Devilwood, Osmanthus americanus; Sweet Shrub, Calycanthus florida; Leatherwood, Cyrilla racimiflora; *Sweet Pepperbush, Clethra alnifolia; *Mountain Laurel, Kalmia latifolia; *Florida leucothoe, Agarista populifolia; *Coastal Leucothoe, Leucothoe axillaris; Spicebush, Lindera benzoin; Virginia sweetspire, Itea virginica; *Dwarf Palmetto, Sabal minor.

PERENNIALS. Cardinal Flower, Lobellia cardinalis; Pitcher Plants, Sarracenia sp.; Rose mallow, Hibiscus Moscheutos; Texas Star Hibiscus, H. coccineus; Joe-Pye Weed, Eupatorium purpurea; Blue Flag Iris, Iris versicolor; Yellow Flag Iris, I. pseudocorus; Louisiana Iris, I. louisiana; Daylillies, Hemerocallis sp.; Swamp Sunflower, Helianthus angustifolius.

FERNS. Autumn Fern, Dryopteris erythrosora; Southern Wood Fern. D. ludoviciana;

Sword Fern, Polystichum minutum


Notes:

1. Fall and early winter are the best times to plant trees and shrubs.

2. Oak tree leaves are especially important as larval food for many caterpillars that are essential in diets of baby birds in the nest.

3. Warning: Southern Magnolia and Sweet Gum trees are considered trashy or very messy due to slow to decompose leaves and hard seed balls, respectively. In very wet settings, Bald Cypress may produce woody “‘knees,” extending up to a foot high, that are a hazard to mowing lawns.

4. Many suggested plants that are not evergreen may have very attractive fall colors before losing their leaves and have berries- important as wildlife food.

Hibiscus cocccineus.by Dr. Judy Stout


Elderberry by Dr. Judy Stout


Ilex vomitoria by Dr Judy Stout


Itea Little Henry by Dr. Judy Stout

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