Ornamental Grasses

A little History

From the early 1900's up to World War II, estate gardeners and a few residential plant lovers in the Northeast planted ornamental grasses in their perennial gardens and landscapes. Many clumps of Pampas grass, Cortaderia selloana and Purple pampas grass, C. jubata were planted only to have them die during the first killing freeze of winter. The plumes were a magnificent sight when standing in the garden even though the plants were dead. (Pampas grass is hardy in Zones 8 to 10.) Some gardeners even dug the clumps and tried to store them over winter for spring planting the next year. Plumes of pampas grass were prized as additions to dried flower arrangements.

From the late 1940's to the early 1950's ornamental grasses became the rage again in the northeast garden and landscape. This time, every plant catalog, garden center and nursery sold them in containers for springtime planting. The only problem, once again, was that most of the ornamental grass species sold at that time were not hardy in the northeast (hardiness Zones 7 and colder). The market collapsed as most gardeners refused to replant each spring only to watch the plants die during winter.

Today, the situation has changed. Ornamental grasses have become the rage on estates, in residential plantings, around commercial landscapes, and as part of rooftop container gardens. Every garden center, nursery and plant catalogue has perennial (hardy) ornamental gasses for planting spring, summer, and fall. Perennial plant growers have taken note of their popularity and have scoured the countryside to find species hardy to northern climates. To demonstrate their popularity, the Perennial Plant Association named Calamagrostis x acutiflora 'Karl Foerster' its plant for the year 2001. 'Karl Foerster' Feather reed grass, a clump-forming grass (hardy in USDA Zones 4-9) grows in full sun to partial shade, thrives in fertile soil that drains well and will perform well in clay to sandy soils.

The plumes (to five-foot tall, light pink at first and then turning to golden tan) are set in motion by the slightest breeze. The flowers are sterile, so no need to worry about this ornamental grass becoming an invasive species.

Propagate by division in spring or fall. Mass plantings are best when spaced 18 inches apart and watered well until plants become established.

Miscanthus sinensis Japanese silver grass (grass blades silvery during summer turning to yellow-tan in fall) grows to 3 to 5-foot tall with purplish flower plumes reaching to 10 foot tall. The flower plumes are fluffy in summer, turning light tan during fall, and stands in the garden through winter.

Variety Flame Grass M. s. 'purpurascens', "purpurascens" means "becoming purple," the colors of grass blades red-orange as of fall, grows blades to 3 to 4 feet with 4 to 6 foot flower plumes in clumping form. It's hardy in Zones 4 to 9. Varieties of M. s., with variegated foliage striped with white include 'Variegatus' and 'Zebrinus', need staking to prevent them from flopping over. Grow in full sun for strongest stems and flower plumes.

Imperata cylindrica 'Rubra', 'Rubra' blood grass, a slow-spreading grass but not invasive, with erect 1 1/2 foot leaves, green at the base and scarlet at the tops, turns all red in the fall. It is hardy in Zones 4 to 9 but I recommend a little protection with evergreen boughs or salt hay in Zone 4. This grass grows well in moist soils but with excellent drainage. Avoid planting in heavy, clay type soil. A little shade during the hottest part of the day improves tolerance to drought.

Festuca glauca Blue fesuce (hardy in Zones 4 to 9) is a clumping grass growing into mounds 6 to 12 inches tall with blue-green or silver-green leaves topped with tan seed heads in summer. The foliage is evergreen, meaning it does not brown during winter. Plant in soil that drains well, filtered bright light to full sun, and prune back in fall or spring to renew growth and keep the clumps neat in appearance. Cultivars 'Elijah Blue' and 'Sea Urchin' are the best for planting as a ground cover or mass planting.

Panicum virgatum Switch grass, a native to the northeast, has made its way into many gardens. This prairie grass grows to 3-foot tall mounds with 4- to 8-foot-tall, silvery or purplish flowers. The flower plumes turn whitish or buff-brown toward fall. The grass blades turn yellow, then brown in fall. Plant in full sun, evenly moist soil. However, it will tolerate dry or boggy soils as well. P. v. 'Haense Herms' turns orange-red in fall and 'Heavy Metal' has metallic blue-green leaves during summer and good yellow color in the fall.

Pennisetum alopecuroides Fountain grass (hardy in Zones 5 to 9) is clump-forming with 2 to 3 foot tall mounds of narrow leaves topped with bottlebrush-like, pinkish to white flowers in mid summer to early fall. The flower stems seem to reach out in all directions. Grows best in full sun to light shade. Fountain grass is a prolific seeder so be prepared to pull up seedlings or cut off flower seed heads before they shatter. 'Hameln' is a compact cultivar reaching to 3 foot tall when in bloom. 'Little Bunny' reaches only 10 to 12 inches tall.

Another North American native, Northern sea grass Chasmanhium latifolium, is clump-forming 2 to 3 feet tall with bamboo-like leaves and showy, drooping seed heads in midsummer. The green seed heads turn to a warm brown as they mature. To prevent spreading of this prolific bloomer, cut back and remove seed heads in the fall, before they shatter. Weed out seedlings in spring. This grass likes full sun in Zones 5 to 9.

Sedges, Carex spp. aren't true grasses but are some of the best grass-like plants for shady gardens and are grown primarily as foliage plants. Carex conica 'Marginata', a clumping 6-inch tall evergreen sedge with narrow 1/8-inch wide leaves dark green with white edges, is hardy in Zones 5 to 9. C. siderosticha 'Varigata' is a handsome, spreading sedge with deciduous green-and-white striped leaves up to 3/4 inch wide. It’s hardy in Zones 6 to 9 (Zone 5 with winter protection).

General planting instructions

CAUTION: Before planting ornamental grasses in the landscape— research, research, research. The plants must be hardy for the Zone in which they are being planted and the plants must not be invasive. Invasive plants can become a nightmare when you end up trying to check their expansion.

Most grasses are best planted during spring to make sure they will be well established before summer heat. Container-grown plants may be planted spring, summer, and fall if adequate water is provided for rooting. For summer planting, clip the tops back by at least one-third to prevent foliage damage until plants are established.

Decorative mulches are beneficial when used around newly planted clumps of ornamental grasses. The mulch keeps the soil from drying and helps prevent weeds. Fall-planted clumps should be mulched with bedding straw or salt hay to prevent winter desiccation.

Cutting back the foliage of over-wintering clumps should be accomplished in late winter, before the new sprouts emerge in spring. This timing can be somewhat difficult as we often have two to three weeks of warm weather in January or February, causing new growth. Make every effort to clip back dried foliage before winter's end. In years past, burning the older dried grasses was a regular practice. It's what happened in nature when the meadows burned during late winter. Of course now, in my area and yours, we cannot burn anyway.

Pest problems like aphids, mealybugs, snails, slugs, gophers, rabbits and deer can be suppressed, if not controlled. Check with your local Cooperative Extension Educator for the latest, least toxic, Integrated Pest Management (IPM) control.