Green Horizons

In the previous issue of Green Horizons, we addressed the topic of some of Missouri’s most unwanted plants, exotic invasives. This article offers information about our state’s beautiful and diverse native plants and how these are a productive choice in a forested riparian buffer.

Prior to the arrival of the first settlers, Missouri’s landscape was vividly colored with native wildflowers (forbs) like Purple Poppy Mallow and Black-Eyed Susans, and millions of acres of native warm and cool-season grasses, trees and shrubs. With the settlement of the state and the later introduction of commercial agriculture practices, many once prominent native species seemed to fade into the horizon. However, distinct benefits are derived by including native plants in landscape plantings, and on a more direct level, into land and forest owners’ riparian buffer systems.

Native plants are beautiful and well-suited to Missouri’s variable weather. They conserve soil and water and provide the backbone for non-polluting landscapes because they don’t need fertilizers or pesticides. They also provide diverse wildlife habitat, require less long-term maintenance than introduced species after plantings are established and contribute to fewer plant losses because they are drought tolerant, winter hardy and resistant to insects and diseases.

These qualities make native plants an excellent choice for use in a riparian forest buffer system. Riparian forest buffers - one of the five practices of agroforestry - are a critical tool for reducing the impact of byproducts from agricultural practices, including sediment runoff and the filtration of agricultural chemicals that may pollute streams and groundwater. Riparian buffers, which consist of a combination of trees, shrubs, native grasses and forbs placed in distinct strips along the streambank, can significantly improve water quality by removing sediment and chemicals before they reach surface water. A well-maintained buffer zone also helps reduce flooding, prevent soil erosion and create wildlife habitat. Additional income can be generated from a riparian buffer by planting trees with future timber harvest or nut production value, or by planting high-value decorative woody florals, such as Curly Willow and Red Osier Dogwood.

Choosing the right match
Matching the right plants to growing conditions is the key to a successful planting. Whether you are planning a riparian forested buffer or a 10-acre reconstructed prairie, native plants - with proper management - will spread energetically through underground rhizomes, bulbs or other natural, vegetative means.

Riparian Buffers, one of the five practices of agroforestry, are living filters comprised of trees, shrubs, forbs, and grasses established in three distinct zones. They enhance filtration of nutrients from surface run-off and shallow ground water,protect the water quality of streams and lakes, and are an effective tool for controlling erosion and providing food for cover for wildlife. Decorative woody florals and berries planted in the shrub zone provide additional income. Lease hunting is another income option, as many types of waterfowl and game birds find habitat in riparian buffer systems.

Dick Schultz, professor, Department of Natural Resource Ecology and Management, Iowa State University, focuses his research on restoration ecology and watershed management and is the leader of the Agroecology Issue Team of the Leopold Center for Sustainable Agriculture, Ames Iowa. Schultz explains that when selecting native species for buffer or prairie plantings, it is important to understand three types of sites. "We break plantings into wet meadows, mesic prairies and dry prairies, and they should each have different sets of grasses and forbs used accordingly," he says. "In addition, the Midwestern corn belt has the richest soil in the world because it developed under prairie vegetation, and should not need any amendments or additives for establishing native plants."

In conjunction with a supply of rich soil, native prairie plants have incredible root systems that support the plants in times of drought. Many of the native grass species are known as warmseason grasses because their root system allows them to be competitive during the hot summer months. Compared with the roots of most non-natives, warm-season grasses and flowers have a deep, extensive root system that helps absorb moisture and prevent erosion. Many species have roots that extend four to eight feet into the soil, while cool-season non-native grasses, such as Kentucky blue grass and smooth brome, extend only a few inches into the soil. The native plants can withstand long periods of dry weather, and do not require watering unless the buffer is established in a small residential or business park setting and is less than one year old.

Laurie Brown, conservation ecologist, Patti Banks Associates of Kansas City, Mo., a natural resource planning and landscape architecture firm, also praises the deep root system of native plants.

"By having this greater root system, native plants are better able to hold soils together," says Brown. "Try taking a clump of turf grass and a clump of native grasses, with roots and dirt, and immerse the roots in a jar of water. You can watch the soil fall off of the turf grass roots, leaving them bare and exposed, while very little soil comes off of the native plant roots."

In recognition of the habitat value provided by native plants, the Missouri Department of Conservation (MDC) has established the Grow Native! program, which is operated in conjunction with the Missouri Department of Agriculture (MDA). Grow Native! strives to protect and restore our state’s biodiversity by increasing conservation awareness of native plants and their effective use. By building partnerships among private industry, non-profit organizations, government agencies and landowners, the program aims to significantly increase the demand for and use of native plants on all landscapes. Information abut native plant species, landscaping and farm guides and information about native plant workshops and events are available on the Grow Native! web site at www.grownative.org.

"Other resources offered by MDC include landscape guides with detailed information for using native plants in home landscapes, and a farm guide that shows how native plants can maximize conservation benefits. The MDA side of Grow Native! Works with native-plant producers and retailers on marketing and businessplan issues," says Barbara Fairchild, Grow Native! communications specialist.

Why plant natives in a buffer?
"Using native plants in a buffer means incorporating plants that are adapted to the local environment - plants that are able to resist native pests and diseases and can survive extremes in weather conditions for that local area," Schultz says. "These are plants that are adapted to the local soils, topography and the competition from other plant species in the riparian ecosystem. They provide specific habitat for local wildlife, butterflies, beneficial insects, etc. It is almost always best to go with native species because of their adaptation qualities."

Schultz explains that natural selection (survival of the fittest) is a powerful reason for the success of local native species. "Introduced species may grow faster, but are susceptible to weather and pests that may be very different from those where the introduced species are native. In our buffer settings, native species also usually have better root systems and provide more protection to the soil and stream compared to introduced species," he says.

One of the most notable benefits of using natives in a buffer is the creation of effective wildlife habitat. "A cool season grass buffer just does not provide much structural habitat, and because it usually consists of only one or two species, there is little plant diversity. Native grasses and forbs provide different heights, densities, shapes of stems and leaves, different flowering times, and different flowers and fruits so that they can attract many more different species of wildlife," says Schultz.

The key is to plant as wide a mix of species as possible to achieve the maximum wildlife benefit. Schultz suggests that planting pure native warm-season grass strips with one or two species is more effective than just one species of low growing cool season grass, but planting 5 or 6 species of native grass and 25 forbs provides much more habitat potential. Similarly, planting mixtures of trees and shrubs will provide more diverse structural habitat, but if a landowner is mainly concerned with upland bird habitat, trees provide perches for predator raptors that may prey on the prairie birds.

Before and after: A riparian buffer was installed at the Iowa State University Bear Creek demonstration area in Story County, Iowa, (left), and the difference in 4 years time (right) was dramatic.

Selecting a variety
Brown comments that there sometimes is no "quick and easy answer" to selecting natives. "The types of plants chosen depends upon soils, amount of sunlight, water levels, frequency and duration of flooding, and adjacent land use," she says. "The type of plants selected is very dependent upon conditions within the buffer."

In addition, a landowner seeking to establish natives plants in a buffer zone has many choices - there were once more than 150 different species of plants found on native prairies.

Schultz recommends visiting the web sites of reputable prairie seed and supply companies to find a list of possible plant mixtures. "Most nurseries provide different mixtures based on general site requirements and seed cost. It is also important to remember that prairie plants usually take longer to establish than non-native cool-season grasses.

"Native trees and shrubs could include any that are usually available from the local state forest nursery. The main consideration here is selecting species that grow on potentially moist sites, and most nursery information includes the kind of sites that different species grow on," says Schultz.

Establishing natives in a buffer zone*
"Most buffers are large enough to require seeding to be cost effective," says Brown. "Plants or plant plugs can be used, but add to the cost of the buffer. If a buffer area is prone to flooding, additional measures will need to be taken (such as erosion control blankets, etc.) to ensure the success of the planting."

Schultz agrees, and adds that his team sometimes plants cover crops to help control weeds while the natives are becoming established. "Prairie grasses and wildflowers (forbs) are usually started from seed, but wetlands are often planted with plugs. Trees and shrubs are planted as 1-2 year old bare-root seedlings."

Site preparation for planting the grasses and forbs in a filter strip can take numerous forms. If the site was previously in pasture, burning down the existing pasture vegetation with glyphosate in the fall and spring, and then using a prairie seed drill will result in a good stand of plants. If the site was previously in row crops, light tilling of the sur-face to kill early weed species, followed by surface packing with a cultipacker and then using a seed drill will provide a good stand. For woody plant establishment, Schultz suggests that site preparation begin in the fall followed by spring planting.

If the site has been in pasture, eliminate competing perennial vegetation in 3-foot or 4-foot wide strips or circles where trees or shrubs will be planted. Fall tillage and/or herbicide application (ex. glyphosate) can be used. If the area has been used for row crops, it is desirable to disk the ground in the spring and seed the area where trees and shrubs will be planted with a mixture of perennial rye and timothy grass.

These cool-season grasses are less competitive with trees and shrubs than other species. Additional grass species recommendations are available at your local NRCS or Missouri Department of Conservation office. Mowing two to three times per year is recommended to control broadleaf and grass weeds.

Many forest nurseries carry one to two-year old seedlings of most tree species for planting in zone 1 of the buffer, the managed forest area. Use high quality stock with good root systems. Quality hardwood seedlings should have a minimum of four to five large lateral roots. Trees and shrubs should be planted in early spring, and make sure the planting holes are completely closed so the roots do not dry out.

Maintenance of natives in a buffer zone*
Maintenance of native plants within a buffer will be highest during the first three years after planting. "This is especially true when using seed," says Brown. "During the first year, native plants spend most of their energy developing roots, so these areas should be mowed frequently to keep weeds under control."

Weed control is essential for survival and rapid establishment of prairie plantings in a buffer, and can be achieved through mowing. Mow as high as possible to allow the native plants to develop their above ground food-producing leaves. Mowing is used primarily to cut off the flowers or seed heads of the weed species that are found at the top of the plant. Burning the prairie plantings in the spring during each of the first 3-4 years will also help control weeds and stimulate prairie plant establishment. Once the prairie is established, a burning cycle of 3-5 years is recommended. Burning regimes are best determined by contacting local natural resource managers with experience in using fire. If burning is not an option, periodic harvesting or very careful .ash grazing may be used. However, if the buffer is enrolled in the Conservation Reserve Program, using the harvested material or .ash grazing are not permitted during the enrollment period of either 10 or 15 years.

For the maintenance of trees and shrubs, mowing and using pre-emergent herbicides are usually needed the first few years. Late fall mowing helps minimize plant damage from rodents during winter months. Mulching is an alternative for woody plants, but if there are several plants spread over a long distance, mulching adds extra expense. Fertilizing a buffer zone generally is not recommended, as most floodplains consist of very fertile top soil.

The use of fast-growing tree species (willow, cottonwood, silver maple and green ash) ensures rapid growth and effective use of nutrients and other excess chemicals that could pollute water. To remove nutrients and chemicals stored in their stems, it may be necessary to harvest these fast-growing trees every 15 to 20 years. If harvested in winter, these species will regenerate from stump sprouts and maintain root system integrity to offer continued protection of the streambank. In most buffer settings there is also the option of planting some slower growing high quality hardwoods that could provide an income source at a later date.

*Portions of this information from the Stewards of our Streams series, produced by Iowa State University. See www.extension.iastate.edu to access these publications.