Ornamental Grasses for Minnesota

Copyright ©  2008  Regents of the University of Minnesota. All rights reserved.

Ornamental or landscape grasses have been used in gardens for centuries. In recent years they have become popular in the United States. However, a lack of information on hardiness and performance in Minnesota has limited their use here.

This fact sheet reports the results of a winter hardiness study in which more than 80 ornamental grasses were grown successfully in USDA Zone 4a where the annual minimum temperature ranged from -20 to -30 degrees F. The research was conducted at the Minnesota Landscape Arboretum. Recommendations for culture and maintenance along with special features of ornamental grasses are also provided.

Desirable Traits

Ornamental grasses can provide an attractive new look in gardens. Desirable traits include:

• Very few insect or disease problems

• Low nutrient requirements

• No maintenance except spring cutback

• More than one season of interest; flowering in spring, summer, or fall, with beauty and color lasting into winter

• Fast growing; large plants grow 5–8 feet tall by the second year

• Varied textures, from fine fescues to coarse giant miscanthus

• Foliage colors of blue, yellow, bronze, red, and also variegated white and yellow

• Movement with the wind providing sound as well as interest and beauty

Culture and Maintenance

In Minnesota, ornamental grasses are best planted in spring. Fall planting may be successful using container-grown plants, but winter protection may be necessary. Local nurseries and garden centers often sell grasses and usually supply large well-developed plants, but typically do not offer the variety that is available from mail order nurseries.

Spacing is determined by the desired landscape effect. A rule of thumb is to space plants equal to their mature height (thus plants 4 feet tall are spaced 4 feet apart), and the rule can be adjusted according to the end result desired. Grasses used as a hedge or screen are generally planted closer together.

Propagation is usually by division (digging the plant and cutting the crown and roots), especially for named varieties or cultivars. Seed propagation, although successful, often results in flower and foliage color variation and requires several years to obtain mature plants.

Large, mature grasses may benefit from spring division, especially if the center of the plant is dead. This can be a major job requiring a sharp ax or spade and a strong back.

Each year in early spring, about the first week in April in Minnesota, cut ornamental grasses back to the ground to remove the previous year's growth. When ornamental grasses are not cut back, spring growth is delayed and the plants look messy and half dead late into the growing season. Manual trimming with a string or electric hedge trimmer works well for a few plants. Large areas can be burned, if burning is permitted and closely supervised. Do not cut in the fall, because winter injury may result, and the winter beauty of the plants will be lost.

Ornamental grasses rarely need fertilization or irrigation after establishment, except in cases of extreme drought or very sandy soil. Most grasses prefer full sun. A few types of ornamental grasses have invasive rhizomes, but most form dense clumps or bunches.

For detailed information and color photos of ornamental grasses, order the 32-page bulletin, Ornamental Grasses for Cold Climates, BU-6411.

Produced by Communication and Educational Technology Services, University of Minnesota Extension.

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