There has never been a better time to explore the beauty of ornamental grasses.
With so many varieties available, there is an ornamental grass for every location, from full sun to shade, as well as for shallow or poor soils.
By incorporating ornamental grasses into your landscape you are adding form, texture, scale, colour (from flowers as well as foliage) and movement. They can also be very luminous and translucent.
We are always looking for plants that offer year round interest as well as being relatively low maintenance. Most ornamental grasses fit the bill. They’re not water hogs, heavy feeders or prone to suffer from pests and diseases. They require little more than an annual trim.
Understanding Cool and Warm Season Grasses:
Cool season grasses:
Actively grow between temperatures above freezing and up to mid 20 degrees Celsius.
Are mostly evergreen (a few are deciduous)
Are mostly low growers up to 2 feet in height.
Mostly flower late winter to early summer.
Warm Season Grasses:
These grasses need warm soil to get growing in Spring.
They grow best when temperatures are over 24 degrees Celsius.
Die back to dormant buds beneath soil surface in the Fall.
Mostly taller growers between 2 to 8 feet, but some get as high as 15 feet.
Start flowering mid-summer to first frost.
Ornamental Grass Growing Tips:
Cut back cool season grasses by no more than two-thirds in early spring (February – March) as new growth starts. Here in the Lower Mainland, you can also lightly trim in September to remove sun burnt foliage. Cool season grasses rarely tolerate being cut back hard.
Removing old dead foliage can be done in several ways: raked out with a fine lawn rake, or by running fingers through the foliage starting from the crown up. This works well when you wear rubber gloves. If you have just trimmed the grass, then rubbing your palm across the top of the trimmed grass usually dislodges dead foliage.
Warm season grasses can be cut back to the ground after the first killing frosts, but most gardeners prefer to leave the dead foliage for winter interest. They therefore only cut them back just before, or as they start to throw out new shoots from March to early April.
If in doubt as to whether your ornamental grass is cool or warm season, the rule of thumb is that if there is still color in the foliage (it’s not all dried and dead) after the first killing frost, then it’s probably a cool season grass and could be cut back to about a half to two-thirds. If all the foliage has died back to ground level and is dried and straw looking, then it’s a warm season grass and can be cut back to ground level ie. 2 – 3 inches.
Take a bit of time planning where in your garden you’re going to locate your warm season grasses as most have highly luminous foliage and flowers. They will look fantastic when backlit, so plant them where they catch early morning or evening sun for best effect, or to the south of the garden.
A common problem when planting is planting too deep as many grasses will suffer or even die if planted this way. Plant to the same soil level as it is in the container. Also, if mulching, do not choke the crown. Taper the mulch down so that there is no mulch touching the crown.
Ornamental grasses rarely require staking. Most are clump forming and they’re not heavy feeders, so require no additional fertilizer.
When dividing ornamental grasses, I recommend that with warm season grasses that you divide them every 3 – 5 years to avoid the center of the plant from dying out. It’s best to do this in early Spring, or at the latest as new shoots emerge from the ground. Dig out the very compact root ball and divide into quarters with a sharp spade or old axe. Then replant to the original soil depth.
It is not crucial to divide cool season grasses but I recommend that they also be divided every 2 – 3 years to get best results. Divide them in the same as warm season grasses and approximately the same time – just as new growth starts.
If deer eat your plants, look at planting Festuca, Miscanthus and Pennisetum varieties.
Use ornamental grasses as cut flowers.
To get best results from cut flower ornamental grasses, cut before the flower has fully opened. The flowers will generally last a couple of weeks in water. After that, drain off the water and let them dry. They will make an excellent dried arrangement that will look good for over a year.
In our next article on grasses we will share the best grasses for specific environmental conditions.