Ornamental grasses are classified as warm season, cool season or tender perennial. They are at their best at different times of the year and require slightly different care, depending on their classification.
Cool Season Grasses, What are They?
Cool season grasses are those that are at their most active growth during the cool season. Growth begins in the fall and often these grasses are the first to flower in the spring garden. As the summer heats up, cool season grasses go into dormancy to begin the cycle again in fall.
Most fescues and carex varieties are popular cool season choices
Cool Season Grasses
- Actively grow between temperatures above freezing and up to mid 20’s degrees Celsius.
- Are mostly evergreen (a few are deciduous).
- Are mostly low growers, 2 feet maximum height.
- Mostly flower late winter to early summer.
Warm Season Grasses, What are They?
As you can expect, warm season grasses are those that are at their most active during the warmest months of the year. Growth begins as the spring sunshine heats the soil. The plant grows and flowers during the warm summer months and enters dormancy as winter approaches. The sun-bleached remnants of the season's growth make for wonderful winter interest and are attractive to birds and small animals.
Sun-bleached foliage and seedheads create winter drama in a usually bleak landscape
Warm Season Grasses:
- Need warm soil conditions to get growing in the spring.
- Grow best when temperatures are above 24 degrees Celsius.
- Die back to dormant buds beneath the soil surface in the fall (perennial).
- Mostly taller growers, 2-8 feet but some as high as 15 feet.
- Start flowering mid-summer to first frost
Cutting back cool season grasses
Cut back by no more than two thirds in early spring just as new growth starts (February-March). In the Lower Mainland, trim lightly in September to remove any sun-burnt foliage if required.
Remove old dead foliage by raking it out with a fine lawn rake, a coarse comb or by running fingers through foliage from the crown up;
We recommend that cool season grasses are divided every 2-3 years to get best results. As with warm season grasses, do so in the early spring or, at the latest, as new shoots emerge from the ground. Dig out the compact root ball and divide it into quarters with a sharp spade, then replant the grass to its original soil depth.
Cutting back warm season grasses
Cut back to the ground after the first killing frosts or, to enjoy the dried foliage over the winter leave uncut until just before or just as plants start to throw up new shoots (March-early April)
Divide every 3-5 years so that the centre of the plant does not die out. This is best done in the early spring or, at the latest, as new shoots emerge from the ground. Dig out the compact root ball and divide it into quarters with a sharp spade, then replant the grass to its original soil depth.