Ornamental Grasses: Advice from a Minnesota Collection

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ornamental grasses

Ornamental grasses shine in late summer and autumn.

Text by Mary H. Meyer for the January/February 2017 issue of Horticulture.

The Grass Collection at the Minnesota Landscape Arboretum began in 1987 as part of a graduate-student research project to evaluate landscape hardiness in USDA Zone 4. Today the collection has approximately 250 taxa in the grass, or Poaceae, and sedge, or Cyperaceae, families. Most taxa are represented by four individual plants so that we can evaluate landscape characteristics and cold hardiness.

The Grass Collection is comprised of 10 large steel edged landscape beds in full sun, each approximately 1,200 square feet, plus 2 beds approximately 3,500 square feet under a wooden lattice shade structure. Chopped hard wood mulch is applied annually to minimize weed competition. No fertilizer is applied and annual rainfall is only supplemented for the establishment of new plants in the collection. The collection is burned in late winter or early spring to remove the previous year’s growth. (Manual cutting back would work as well, but the size of the collection prohibits it. The burn crew from the arboretum carries out the spring burn.)

The goals of the collection are fivefold:

  • We grow and publicly display a wide variety of ornamental and native grasses and sedges in Zone 4.
  • We strive to provide information on the hardiness and landscape use of grasses and sedges for all landscapes, but especially for cold climates such as Zone 4.
  • We compare cultivars for distinct differences and we show these plants so that the public and nursery industry can see and compare these selections.
  • We use the grass and sedge collection for formal and informal educational classes and events.
  • Finally, we aim to provide a collection of grasses and sedges for study and comparison for taxonomic and research purposes.

Don’t be intimidated by grasses! They are easy to grow. Match the plant to your site and soil type. Maintenance is simple: using hand pruners or an electric hedge trimmer, cut back the tops in early spring or late winter. Learn more at grasstalk.wordpress.com.

Three favorites at the UMN Grass Garden
Sporobolus heterolipis ‘Tara’ is a 24- to 30-inch-tall, uniform form of the native upland grass prairie dropseed. ‘Tara’ is shorter with tufted fine foliage that grows in a dense bunch. The light, airy flowers form round beadlike seeds with a very characteristic fragrance, smelling like hot buttered popcorn or coriander and cumin. It’s easy to grow but may be slow to establish. It prefers dry, well-drained soils and spring propagation, and it can be used in mass to cover slopes.

Common in tall and shortgrass prairies, little bluestem (Schizachyrium scoparium) prefers mesic (medium) to dry sites. It is an excellent grass for dry sites, slopes and lighter gravely soils. Plants can readily self-seed and are easy to grow, especially on poor soils. The foliage is larva food for many skipper butterflies. Blue Heaven® is a University of Minnesota selection with upright blue foliage in summer and showy burgundy fall color; it grows three to four feet in height.

Carex pensylvanica, or Pennsylvania sedge, is native to oak woods and dry wooded sites throughout much of the Northeast and the central United States. This 6- to 12-inch, fine-textured grass-like sedge will also grow in full sun, although the foliage may scorch. It can be used as a lawn substitute, but it will not tolerate foot traffic. It can be mowed in early spring or raked to remove old foliage. It’s good for steep slopes and difficult sites, but it may be slow to establish. Lack of seed propagation limits greater use of this native plant.

Mary Meyer is a professor and extension horticulturist at UMN and the author of the Grasstalk blog.

Image credit: Frederic Collin/Moment/Getty Images