Selecting Native Plants for Wetland, Riparian, and Wildlife Buffer Plantings

by Richard T. Haard, Ph.D., Propagation Manager, Fourth Corner Nurseries

For the past 15 years the protection and enhancement of wetlands has become a major mission for state and federal governments. With the passage of the Clean Water Act, the new regulations have affected how we practice agriculture and conduct commercial and residential developments. In addition, riparian habitats have been enhanced or given protection, in part because of the listing of some fish species under the Endangered Species Act.

Government mandates as these are considered by some as an unwanted expense in business. Sometimes this economically painful chore is a necessary action that we must take to be sure there will be fish, wildlife and natural habitat to share with our future generations. Wetlands are our reservoir of ecological diversity and also the way in which the environment is cleaned of toxins, assuring water quality and soil conservation in order to sustain our own presence on this planet.

This obvious importance of maintaining functional wetlands and wildlife habitat has also brought about an independent movement of farmers and residential landowners who want to enhance natural or man-made wildland or wetland habitats on their property for recreation and aesthetic purposes.

In recent years there has been an upsurge in naturalized landscaping, pond gardens or the construction/enhancement of man-made streams in the commercial landscape. Some farmers are beginning to think beyond the organic farming agenda to land management strategies which allow them to integrate their actions into a landscape plan that includes wild things. Bioswales and stormwater detention ponds are becoming
more common ways of integrating the many benefits of wetlands even into urban areas.

Selecting Wetland Plants

Selection of the proper plants is an important step in achieving the benefits of wetlands. Plants can be divided
into four groups, which relate to their occurrence in wetland habitats:

1. Obligate (OBL) plants almost always occur in wetlands

2. Facultative wetland (FACW) plants generally occur in wetlands more than 67 percent of the time

3. Facultative (FAC) plants occur equally in wetlands and uplands

4. Facultative upland (FACU) plants usually occur more than 67 percent of the time only on upland sites.

This catalog provides information on habitat preferences; however, consulting your local flora and the USDA Plants Database when planting into a natural environment is advisable. If some of these natives are to be moved into manicured and irrigated landscapes, considerable latitude in habitat specialization is possible.

Selection of the correct species is critical. Beyond these habitat specializations, many of our species offered in this catalog are provincial – that is, they are native only to certain places. To use a native plant strain or species outside of its natural realm comes with a risk of introducing a new weed or genetic contamination of related species. Please be responsible in your use of native plants.

After selecting plant varieties, determine the necessary plant size and type (container or bare-root). The plant size you need depends on how long you can wait for results. If you need trees above the “weeds” in one or two years, then select larger plants (these will be more difficult to establish). If you can do the maintenance, then smaller plants will perform better because they adapt to transplanting quicker. It’s the ratio of roots to top that affects transplant establishment.

Container vs. Bare-root Plants

We are primarily a bare-root nursery, with a limited selection of northwest native plants in containers. We sell our bare-root plants to many growers who use them in container stock.

Bare-root seedlings are the least expensive and range in size from a few inches to 6 feet tall and more. Comparing plants of equal size, those in containers are more expensive than bare-root plants due to growing costs. If price is your primary consideration, bare-root plants can be used, but timing and handling considerations must be factored in.

Bare-root trees and shrubs generally are available only during dormancy. In our cool, moist Western Washington climate, they can be used from first harvest in late November through late April. Other regions have their own windows of opportunity for bareroot use, so be sure to find out what is best in your area.

Well-rooted container plants can be used any month when soil moisture is adequate. They are the preferred choice for late spring to early fall plantings.

Establishment in the Field

When wetlands are restored, a primary objective is often to re-create the “natural” hydrology of the site before alteration. Generally, ditches and other drainage structures are closed, allowing water to cover the site. In constructing artificial wetlands, a basin is excavated, stockpiling the topsoil. Following final grading and contouring of the excavated basin, the topsoil is replaced. As the hydrologic function returns and stabilizes, distinct zones may develop on the site that affects vegetation. Because of drainage or soil conditions, some sites within the wetland are best suited to a particular plant species. Attempts to establish unsuitable plants are futile and expensive.

Remember that newly-planted tree, shrub, and forb seedlings may not survive the hydrology that mature plants can and may be lost soon after planting. It may be necessary to restrict or delay the flooding of wetland areas for a year or so to allow the plants to become established.

To match vegetation to the wetland, the hydrology of the site must be evaluated. Contour maps that show levels of inundation and soil saturation during the growing season are useful in planning revegetation. By comparing hydrology, soils and native plants of functionally similar adjacent wetlands, distinct zones can be identified. Then adapted species or mixes of normally occurring species can be selected.

When an area does not have distinct zones that are particularly well suited for a given species, a mix of species can be planted across the entire site. This may be the practical approach on newly constructed wetlands that have been graded to remove major drainage patterns, or where hydrology is uncertain. Species that are adapted to the site will survive, while the others die off.

As the hydrology stabilizes, adapted species will become established and other native plants will move in. On urban sites, native wetland grasses and forbs may be introduced to complete the landscape when the trees and shrubs are established. Planting density depends on the goals and scope of the project. Urban wetlands may feature specimen plants representing the desired landscape. In large reconstructed or new wetlands, more plants may be desired. Hardwood plantations generally are established at 10×10-foot to 20×20- foot spacing. This represents 435 trees per acre at a 10×10 spacing and 108 trees per acre at a 20×20 spacing.

The importance of selecting healthy, vigorous planting stock suited to specific site conditions cannot be overemphasized. It’s a waste of time and money to try to establish plant species that are poorly-suited to your site.