By Raakel Toppila
The ornamental value of grasses has only recently been recognized. Their graceful habit, animated movement, and fine textured foliage have proven them a worthy addition to our gardens. However, the ornamental value of our own native grasses has yet to be discovered.
Warm or Cool Season Grasses
Grasses are often described as either warm or cool season. These characteristics do not refer to the hardiness of the plant but to their season(s) of growth.
Cool season grasses begin to grow in late winter or early spring. The optimum temperature for growth is between 15 and 23 degrees Celsius. They flower in late spring and summer. Growth slows or the plant enters a period of dormancy in the hot summer months. When temperatures cool in the fall they begin to grow again. Some even continue to grow throughout the winter months.
Warm season grasses thrive in the heat of summer. They grow best at temperatures between 26 and 32 degrees Celsius. They produce flowers during the summer months and go dormant in the fall. Dormant foliage and seed heads of warm season grasses persist providing winter interest and food for birds.
A second way to classify grasses is by their habit. Some are described as clump forming, bunching, or tussock grasses. These types of grasses spread by tillers and create a compact, clump-like growth. In a garden setting these grasses are often preferred as the plants remain contained within their planting area.
Running grasses spread by rhizomes (under ground) or stolons (above ground). Running grasses may become invasive through their ability to form dense mats quickly. Running type grasses are often used as lawns.
It is also important to be aware of the likelihood of a grass to self-seed. Chasmanthium latifolium, Northern Sea Oats, for example, is a clump forming North American native grass that produces a multitude of seeds, many of which germinate the following year. This grass can spread quickly in the garden and may become a problem. Despite this drawback, Northern Sea Oats is known for it's unique seed heads. One way to control its spread is to cut the grass to 10 centimetres in height soon after the seeds appear.
Once established, ornamental grasses require very little maintenance. The frequency of watering can be adjusted to the individual needs of the grass species. Most grasses have few, if any, pest or disease problems. Perhaps the most important maintenance technique is cutting back the grass to a height of 10 centimetres. This can be done with hedge shears in February or March before new growth appears from the crown of the plant.
Dividing is another maintenance technique that is required for clump forming grasses. As the plant ages it may flop or die in the center. Division will help rejuvenate the grass and keep it looking its best. Divide warm season grasses in late winter or early spring. Cool season grasses can be divided in the fall, winter or early spring. Cut the foliage back to a height of 10 centimetres. Remove the clump from the ground leaving soil around the root ball. Use a saw, spade or shovel and divide into smaller clumps. Keep in mind, the smaller the clump, the longer it will take to reach full size. Share the divisions with friends or transplant back into the garden.
Some Native Ornamental Grasses to Try
Big Blue Stem, Turkey Foot
- Clump forming, warm season, perennial grass
- 1.2 - 2.0 meters tall
- Blue green to silvery blue foliage with purplish flower spike
- Dry soils, open prairies and shores from Saskatchewan to Quebec.
- Full sun, well-drained soil, tolerant of considerable drought.
- Screens, erosion control, specimen, masses, winter interest, arrangements.
Side Oats Gramma
- Clump forming, warm season, perennial grass
- 0.3 - 0.6 meters tall.
- Gray green fine textured foliage produces a one-sided arrangement of purplish flower spikes in early summer.
- Dry prairies and sand hills from southern Ontario to Saskatchewan.
- Drought tolerant and adaptable to a wide range of conditions. Grows best in well-drained fertile soil in full sun.
- Use in masses, for erosion control or in arrangements.
- Slow spreading, cool season, perennial grass 0.6 - 1.0 meters tall.
- Foliage resembles palm fronds giving it a tropical appearance.
- Moist or swampy ground from Manitoba to Ontario.
- Moist conditions are required. Tolerates either sun or shade.
- Use in masses along streams, at the edge of a pond, in water gardens, pots or tubs.
- Clump forming, cool season, perennial grass 0.3 - 1.0 meters tall.
- Forms dense clumps of dark green foliage.
- Flowers are showy loose panicles.
- Damp soils, shorelines and meadows from Alaska to Newfoundland to southern United States.
- Moist, rich soil in light shade.
- Use in masses or as specimens, along streams or on slopes.
- Clump forming, cool season, perennial grass 0.3 - 0.6 meters tall.
- Tufted grass with shiny foliage and loose, delicate flowers.
- Dry open soil from Newfoundland to British Columbia.
- Grows best in light shade and moist conditions. Tolerant of dry soils.
- Planted as a specimen or in masses.
All images courtesy of Arlene Neilson, unless otherwise indicated.