The Right and Wrong of Native Grasses

The surge of interest in using ornamental grasses in landscape designs has recently shined the spotlight on some of our best native grasses. These cold-hardy, drought-tolerant and low-maintenance plants are now being used in a wide variety of settings, from large prairie meadows to native grass gardens. The benefits include no need for irrigation, fertilizers, fungicides or insecticides, and few, if any, herbicides.

There are hundreds of grasses native to the prairies, meadows and woodlands of the high-rainfall areas of the Midwest and eastern United States. A few stand out as being the most ornamental, longest-lived and adaptable to a variety of growing conditions. Many of these grasses can be readily established from seed, and all can be installed as transplants. Most grow in sunny situations of at least a half a day of full sun, but some do best in moderate shade and many will grow in very difficult soil conditions. There is a native grass for practically any situation.

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Table 1.
TALL GRASSES
Latin Name Common Name Soil Conditions Sun
Andropogon gerardi Big bluestem Clay, loam, sand Dry to moist Full sun to light shade
Panicum virgatum Switchgrass Clay, loam, sand Dry to moist Full sun to light shade
Sorghastrum nutans Indiangrass Clay, loam, sand Dry to medium moist Full sun to light shade
Spartina pectinata Prairie cordgrass Clay, loam, sand Moist to wet Full sun

TALL GRASSES FOR SUN

The tall grasses (5 to 8 feet tall) are best used where you desire a strong architectural element, and as a backdrop for short grasses and other plants. Switchgrass, reaching 5 to 6 feet tall, is commonly used in “New American Garden” plantings, popularized by Wolfgang Oehme and James von Sweden. Switchgrass stands up better over winter than all other native grasses, and provides excellent winter cover for wildlife. Indiangrass is particularly showy in the fall, with brilliant golden plumes of seeds. Big bluestem turns bright red in the fall, and is distinctive for its three-parted “turkeyfoot” seedheads. Prairie cordgrass sports long, graceful leaves, and is excellent for stabilizing wet streambanks, shorelines and other moist soil situations.

SHORT GRASSES FOR SUN

The short grasses (1 to 3 feet tall) are at their best when planted in foreground situations where they can really show off. Prairie dropseed is considered by many to be the most elegant of all the native grasses of North America, with its fountain-like emerald green leaves flowing out from a tight clump. The crimson fall color of little bluestem is stunning, planted in small groups or in large meadows. Blowing in the wind, a field of little bluestem bears a striking resemblance to waves on the ocean. It thrives on dry, sandy soils, but is not recommended for clay.

Broomsedge, a close relative of little bluestem, is an excellent grass for planting on nutrient-poor, acid clay soils (down to a pH of even 4.0). It puts on a fall color show similar to that of little bluestem. Side oats grama is best known for its low growth habit (2 to 3 feet) and its ornamental seedheads. This is an excellent grass for planting on extremely dry soils and can tolerate heavy foot traffic and close mowing (down to 1 inch).

Table 2.
SHORT GRASSES
Latin Name Common Name Soil Conditions Sun
Andropogon virginicus Broomsedge Clay, loam Dry to moist Full sun
Bouteloua curtipendula Side oats grama Dry to medium Full sun
Chasmanthium latifolium Northern sea oats Clay, loam Medium to moist Full sun to full shade
Diarrhena americana Beakgrass Clay, loam, sand Medium to moist Light to medium shade
Schizachyrium scoparium Little bluestem Sand, loam Dry to medium Full sun
Sporobolus heterolepis Prairie dropseed Loam, sand Dry to medium Full sun

SHORT GRASSES FOR SHADY SITUATIONS

Northern sea oats produces fabulous glittering seedheads in the fall that are distinctive from all other native grasses. It prefers light to medium shade in a damp to medium soil, and is excellent for planting under the dappled shade of oaks, hickories and ash trees, as well as on the woodland edge. Beakgrass is a grass that occurs naturally in moist woodlands and river bottoms, but thrives in good garden soil in semi-shade. The deep green glossy leaves of beakgrass make it distinctive, and it looks great when planted in a mass.

NATIVE GRASS CULTIVARS

There are an increasing number of selections of native grasses becoming available on the market. Some of the best cultivars include:

  • Broomsedge (Andropogon virginicus): Silver Beauty.

  • Switchgrass (Panicum virgatum): Campfire, Cloud Nine, Dallas Blues, Heavy Metal, Northwind and Shenandoah.

  • Indiangrass (Sorghastrum nutans): Sioux Blue.

  • Little bluestem (Schizachyrium scoparium): The Blues.

  • Prairie cordgrass (Spartina pectinata): Aureo-marginata.

Many new varieties of native grasses are now being offered by various nurseries across the United States. Trials involving different cultivars, including little bluestem, big bluestem and prairie dropseed, are bringing new ornamental grasses to the marketplace.

ESTABLISHING NATIVE GRASSES

There are two methods for establishing native grasses: transplanting or direct seeding. Transplants typically mature in the year you install them, and are best used in high visibility areas where you require instant results. Direct seeding typically requires two to five years to reach maturity, depending upon the species. Transplants are far more costly than seeds, with an average installation cost between $1 per square foot using small plugs, up to $10 per square foot using gallons*.

The cost to establish one acre of prairie meadow from seed, including wildflowers, ranges from 7 to 12 cents per square foot, depending upon the composition of the seed mix and the cost of site preparation. A prairie meadow seeding consisting of only native grasses, with no prairie wildflowers, can cost as little as 2 to 3 cents per square foot, assuming extensive site preparation is not required.*

PREPARING THE SITE FOR PLANTING NATIVE GRASSES

The first step to successful establishment of native grasses, using transplants or seeds, is to prepare the site properly prior to planting. You must completely eliminate all existing perennial weeds. This may require a full year or possibly longer, depending upon the vegetative cover you'll have to remove. Old fields that have grown up to perennial weeds can take up to two years to prepare. Some of the most difficult perennial weeds to eradicate include Canada thistle, Canada goldenrod, quackgrass, Johnsongrass, horsenettle, bindweed and mugwort, to name a few. You must eliminate these aggressive, pernicious weeds prior to planting or seeding. You can accomplish this using the appropriate herbicides for a full growing season, at intervals of every six to eight weeks. Do not allow the weeds to go to seed during the site preparation process, as this will only worsen the situation. Regular, repeated sprayings are required for full weed control. If perennial broadleaf weeds are present, you will need to apply the appropriate combination of broadleaf herbicide with a strong solution of Roundup for the first two applications. In situations where pernicious perennial weeds are present, you may need a second year of treatment prior to planting.

Turfgrass is easy to kill using a single application of Roundup in the fall or spring, or by smothering it with black plastic for two to three months during the growing season. You can also remove turf using a sod cutter in preparation for planting. If perennial weeds are present in the sod, you will likely need to perform repeated applications of Roundup for a full growing season. If you decide to smother weedy turfgrass, you should do so for one full growing season. A sod cutter typically will not completely remove the roots of perennial weeds, and you should use this method only on weed-free turf.

Once you have eliminated all perennial weeds, you may amend the soil, if necessary. Heavy clays and dry, sandy soils benefit greatly from the addition of organic matter, such as composted leaves, grass clippings, manure and mushroom compost. You should mix the composted material into the upper 6 to 12 inches of soil, the primary rooting zone of most grasses. Some native grasses have roots that can extend more than 8 feet into the soil. It is not recommended that you use peat moss, sawdust and wood chips, due to their tendency to consume the nitrogen in the soil.

Work compacted soils to well below the zone of compaction to break up the soil that would otherwise impede the infiltration of air and water into the soil, preventing proper root development.

When seeding native grasses on large areas, it is not cost effective to add organic matter to the soil. With careful attention to the soil conditions, you can select the best native grasses to grow on even the most hostile clay soils and dry, sandy soils. For instance, little bluestem thrives in poor, dry sand, while big bluestem and switchgrass do great in terrible clay soil. By selecting the right grass for the right situation, you'll rarely have to add soil amendments.

Table 3.
NATIVE PRAIRIE GRASSES FOR CLAY SOILS IN FULL SUN
Latin Name Common Name Seeding Rate for Solid Stand Optimal Seeding Date
Andropogon gerardi Big bluestem 8-12 lbs. per acre Mid-spring
Andropogon virginicus Broomsedge 8-12 lbs per acre Mid-spring
Panicum virgatum Switchgrass 5-8 lbs. per acre Mid-spring
Sorghastrum nutans Indiangrass 8-12 lbs. per acre Mid-spring

ESTABLISHING NATIVE GRASSES USING TRANSPLANTS

After you've properly prepared the site, you can install transplants in much the same way you would any other perennial. You can control weed germination at the time of planting by applying a pre-emergent herbicide after you've installed all the plants. Never apply pre-emergent prior to planting, as the herbicide may end up in the planting hole, causing clubroot in your grasses. Mulch with 3 inches of clean straw or shredded bark to help keep weeds at bay. A combination of pre-emergents and mulch will result in a virtually weed-free planting in the first year. Once the grasses are well established in the second year, their dense fibrous roots help to exclude weeds, making the planting truly low maintenance.

MAINTENANCE OF NATIVE GRASS GARDENS

You may have to pull the occasional weed or dig out of the grass bed from time to time. If broadleaf weeds become a problem, you can control them by using the appropriate selective herbicide, such as 2,4-D, dicamba or MCCP. Of course, one of the goals of the native grass garden is often to reduce or eliminate herbicide use, so alternative weed control methods are often preferable. The best management technique (and often the most fun) is to burn the grasses back to the ground in spring. You may choose to allow native grasses to stand over winter for their ornamental effect and to provide winter cover for wildlife. After that, you can either burn them or cut them back to the ground in early to mid-spring. Make sure to take the necessary precautions if you are burning your grasses. This includes having a ready source of water on hand to keep things in control (a hose is usually sufficient in small areas). Always make sure that the area you are burning is not near other flammable materials, such as wooden structures, vinyl siding (which has a very low melting point) or other readily combustible vegetation.

ESTABLISHING NATIVE GRASSES BY DIRECT SEEDING

Direct seeding native grasses is more complex than installing transplants in a garden setting, but can yield outstanding results at a fraction of the cost. Controlling weeds prior to seeding is absolutely essential to success. Proper selection of grasses that are best suited to the site conditions is also critical. Select only those grasses that are known to grow in your soil conditions. A plant that might thrive in the garden with a little help may have only a slim chance of surviving when direct seeded into a soil to which it is not adapted.

Table 4.
Native Prairie Grasses for Dry, Sandy and Rocky Soils in Full Sun
Latin Name Common Name Seeding Rate for Solid Stand Optimal Seeding Date
Bouteloua curtipendula Side oats grama 8-12 lbs. per acre Mid-spring
Schizachyrium scoparium Little bluestem 8-12 lbs. per acre Mid-spring
Sporobolus heterolepis Prairie dropseed 8-12 lbs. per acre Fall, early spring

The majority of the native grasses mentioned in this article are warm-season grasses, meaning that they grow best in warm temperatures. Most grow best in USDA Hardiness Zones 4 to 8, although a few go into Zone 3, and others into Zone 9. The best time to plant warm-season grasses is in mid-spring. Most warm-season grasses will not germinate until the surface soil reaches a temperature of 70 or 80°F. Unlike cool-season turfgrasses, fall or early spring seedings are not recommended for warm season grasses.

Fall seeding of warm-season prairie grasses behave as dormant seedings, with germination occurring the following spring. Warm-season grasses typically exhibit lower germination rates when seeded in the fall, compared to mid-spring seedings. Therefore, fall seeding is not recommended, except for prairie dropseed, which does best when planted in early spring, or as a dormant fall seeding. Planting prairie dropseed after May 15 in the Upper Midwest typically results in poor germination. Northern sea oats also prefers cooler soil temperatures for germination, and is best seeded in early to mid-spring.

All of the native grasses mentioned in this article grow in well-drained loamy soils, with the exception of the moisture-loving prairie cordgrass. Certain native grasses thrive in difficult soil conditions and can be used to solve landscape problems where soil amendment is not an option. Some of the toughest natives for growing on difficult sites are listed in Tables 3 (page C8) and 4 (above).

The general rule of thumb when you're seeding native prairie grasses is to plant 40 seeds per square foot. The seeding rates listed above vary from 25 to 60 seeds per square foot. You should use the lower seeding rates only for mid-spring seedings on well-prepared sites (except for prairie dropseed, which you can seed in the fall). You should use the higher seeding rates when planting on difficult soils, for fall dormant seedings or in areas that have a history of heavy weed growth and where you anticipate a lot of weed pressure.

If you'd like to establish a mixture of different grasses, simply divide the solid stand seeding rate for each grass by the number of species you'll plant together in the mix. The resulting seeding rates for each grass will provide an even mixture of the desired grasses. Exceptions to this rule are big bluestem and switchgrass, which tend to be aggressive. It is a good idea to reduce the seeding rates of these grasses if you use them in a mixture, especially with the shorter grasses. You can increase the seeding rates for the shorter grasses in the mix to make up the difference.

Northern sea oats, beakgrass and prairie cordgrass are somewhat more difficult to establish using seed, or require specific growing conditions. Direct seeding for establishment of these is not recommended.

SEEDING METHODS

You can plant native grasses mechanically using specialized seeders on large areas of a half acre or more, or by hand-broadcasting on small areas. The two types of seeders that work well for planting native grasses are a no-till drill-type seeder and drop-type seeder, outfitted with optional “grass brushes.”

The no-till drill seeder works well for seeding into firm, smooth, dead sod. The no-till feature prevents bringing up weed seeds when you're preparing the seedbed, resulting in lower weed densities. The drop-type seeder requires loose soil, and is recommended for sites you've already worked up during site preparation.

MAINTENANCE IN THE FIRST TWO YEARS: MOWING BACK THE WEEDS

Most native grasses grow slowly and require two or more years to reach full development. Annual and biennial weeds are often a problem in the first two years, but you can control them by mowing. Keep weeds mowed to a height of 6 inches early in the first year and at 12 inches later in the year if the native grasses grow higher than six inches tall. Mow just above the tops of the native grasses. This prevents the weeds from smothering the smaller grass seedlings. Expect to mow two to three times in the first year. Do not allow the weeds to grow over 12 inches tall before mowing, or the mowed material can smother the small seedlings.

In the second year, mow in early June at a height of 12 inches. This will knock back annual and biennial weeds. Many native grasses will begin to grow vigorously in the second growing season, and some may flower (side oats grama and Canada wild rye often bloom late in the second year). If weeds continue to be a problem later in the second year, mow again just above the tops of the prairie grasses. A flail type mower works best, as it chops up the material so that it dries rapidly without smothering the smaller grass seedlings below. Rotary mowers often lay down the cuttings in piles, which can smother the young prairie plants.

You can control many weeds using selective herbicides, if desired. You can use broadleaf herbicides to control non-grassy weeds in native grass plantings. Plateau (imazapic) herbicide will control most broadleaf weeds, as well as many cool season perennial grasses, such as quackgrass. Plateau is labeled for use on most warm season grasses, such as big and little bluestem, broomsedge, Indiangrass and side oats grama. Warning: Plateau kills switchgrass, so never use it in plantings that contain this grass.

LONG-TERM MAINTENANCE: CONTROLLED BURNING OR MOWING IN THE THIRD YEAR

The easiest method of managing warm-season native grasses is to burn them off in mid-spring. This removes all the old debris to make way for new, fresh growth. It also helps prevent invasion by trees and shrubs, and controls unwanted cool-season grasses such as quackgrass, bluegrass, bromegrass and fescue. Wait until mid-spring to burn, after cool-season grasses and weeds have begun active growth (when they are 4 to 6 inches tall). The fire will set back unwanted cool-season plants, while the prairie grasses remain dormant and unharmed underground.

If burning is not an option, mowing and raking the cuttings in mid-spring is a good alternative. The grasses should be cut as closely to the ground as possible, just after the first lawn mowing of spring. Mow the native grasses right down to the soil if possible, in order to do maximum damage to cool-season grasses and weeds. Rake the cuttings to expose the soil to the warming rays of the sun. This mimics the effects of fire, resulting in a rapid increase in soil temperature that favors the warm-season native grasses.

LOW COST, LOW MAINTENANCE

Native grasses can be an attractive, low-maintenance and cost-effective alternative to turfgrass and other higher-maintenance landscapes. The initial cost of seeding native prairie grasses is usually less than that of a lawn. They don't require an irrigation system and require few, if any, pesticide applications once the grasses are established. Prairie meadows composed of native grasses and wildflowers create stunning four-season landscapes that provide a home for birds, butterflies and many other forms of wildlife. The result is a relatively care-free, natural landscape composed of long-lived perennials that return year after year for decades to come.

The life cycle costs of prairie meadows and native grass plantings are among the lowest of any landscape when factored over the 20, 30 or more years that they will live. Cost savings include reduced labor, lower machinery costs and repairs, and the virtual elimination of fertilizers and pesticides. Native grasses make good ecological and economic sense. Expect to see these tough, yet beautiful plants used in an increasing array of landscape situations in the future.

*All costs include labor.

Neil Diboll is president of Prairie Nursery Inc. (Westfield, Wis.).

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