Landscape Plants for Wet Sites

— Written By and last updated by Sarah Roberson

Wet, poorly drained soils present one the most difficult challenges for growing plants in the landscape. Excessive moisture displaces oxygen in the soil and plant roots can suffocate as a result. Many plants are intolerant of having their roots submerged for extended periods of time. Even though standing water may not be present, poor drainage is often responsible for reduced growth and survival of plants in our landscapes. Since we have had more than our share of rainfall lately, I thought you might find an article on plants for wet sites interesting. For your information ornamental plants in the landscape that perform poorly under wet conditions like we have had are azaleas, Japanese hollies, dogwoods, ligustrum, junipers, and ornamental cherries to name a few. If you have any of these plants with problems that can’t be linked to anything else then just dig around the base of the plant and check the soil moisture. If there is water standing or oozing into the hole from the soil or when you squeeze the soil water drips out like wringing out a sponge then it is too wet.

When landscaping sites with poor drainage it is advisable to start with plants that are tolerant of those conditions. Plants native to wet bottomland areas often thrive under these conditions. When selecting and planting trees and shrubs for poorly drained sites, it is important to recognize that plants often need to acclimate to these conditions before they are able to tolerate flooding and low aeration. Even plants that are very tolerant of poor drainage will have shallower root systems on poorly drained sites. Over time, physiological and anatomical changes in the plant can also help to improve tolerance to poor drainage. As a result, it is often desirable to start with small plants that have been grown under conditions as similar to the planting site as possible when planting trees and shrubs on poorly drained sites.

Although many of plants listed in this article can tolerate poor drainage, their growth will often be improved if more desirable growing conditions can be provided. Creation of raised beds, swales, grassed waterways, and drainage lines can help to divert and route excess water away from planting sites and should be considered if drainage is excessively slow. Notice that the first tree on the list is red maple, not the Japanese maple, but our native red maple, Acer rubrum. This is one of the trees most tolerant of wet sites. It is also one of the most commonly planted shade trees in any landscape including well-drained sites. Planting them in well-drained sites or in areas where they are competing with the lawn for water results in poor performance because they are attacked by an insect called gloomy scale. River birch, Betula nigra, is on this list also. If you have a well-drained yard and want to have yellow leaves falling during summer droughts then plant river birch, if not avoid it in well-drained yards.

Below is a list of plants for the landscape that can tolerate varying degrees of wetness. I have deleted plants that are not good landscape plants for one reason or another. Plants with an * following their name indicates that those species have been known to tolerate flooded conditions for extended periods of time. This is of course not a complete list of everything that is tolerant of wet conditions. For more information on gardening in Pitt County, call the Master Gardener Volunteers at 902-1705. You can also email questions to pittcomgv@hotmail.com. Their office hours are Monday through Friday from 10 a.m. to noon. You can find more gardening information at http://pitt.ces.ncsu.edu.

TREES

Acer rubrum (red maple)*

Aesculus pavia (red buckeye)

Betula nigra (river birch)*

Magnolia grandiflora (southern magnolia)

Magnolia virginiana (sweetbay magnolia)*

Pinus taeda (loblolly pine)

Quercus bicolor (swamp white oak)

Quercus laurifolia (laurel oak)

Quercus lyrata (overcup oak)

Quercus nigra (water oak)

Quercus nuttallii (nuttall oak)*

Quercus palustris (pin oak)*

Quercus phellos (willow oak)

Quercus virginiana (live oak)

Taxodium spp. (baldcypress)*

Thuja occidentalis (eastern arborvitae)

Thuja plicata (giant arborvitae)

Ulmus alata (winged elm)

Ulmus parvifolia (lacebark elm)

SHRUBS

Baccharis halimifolia (groundsel bush)

Callicarpa americana (purple beautyberry)

Cephalanthus occidentalis (button bush)*

Clethra alnifolia (summersweet)

Cyrilla racemiflora (swamp cyrilla)

Euonymus americana (American euonymus)

Fothergilla spp. (fothergilla)

Hibiscus syriacus (rose-of-sharron)

Ilex cassine (dahoon holly)

Ilex glabra (inkberry)

Ilex verticillata (winterberry)*

Ilex vomitoria (yaupon holly)*

Illicium spp. (anise-tree)

Itea spp. (sweetspire)

Lindera benzoin (spicebush)

Myrica spp. (bayberry/waxmyrtle)

Rhododendron arborescens (sweet azalea)

Rhododendron atlanticum (coastal azalea)

Rhododendron vaseyi (pinkshell azalea)

Rhododendron viscosum (swamp azalea)

HERBACEOUS PERENNIALS

AND SHALLOW WATER/BOG PLANTS

 Astilbe spp. (astilbe)

Canna x generalis (Water canna)*

Carex spp. (sedge)

Eupatorium dubium (Joe Pye weed)

Hibiscus moscheutos (rose mallow)

Iris ensata (Japanese water iris)*

Iris laevigata (water iris)*

Iris pseudacorus (yellow flag)*

Iris siberica (Siberian iris)

Iris vericolor (blue flag)*

Iris virginica (southern blue flag)*

Lobelia cardinalis (cardinal flower)

Sarracenia spp. (pitcher plant)