Ornamental perennial grasses have been catching on in the gardens for a while now. But for the uninitiated, they add height, colour and a spiky texture that is unique to this group of perennials. Depending on the size, some species add the additional dimension of sound (rustling) and movement (swaying) in lazy summer breezes.
They start growing earlier than most other plants, soon shooting up seed heads in early summer, often double to triple the height of the foliage. Into the fall, the foliage and seed heads turn a tawny brown and, depending on the species, they provide visual interest throughout the winter. If you do leave the foliage for the winter, you have to be quick about cutting it back in spring as soon as the snow melts to avoid also cutting the early sprouting sprigs. Or you can avoid the rush and cut them back in the late autumn before snowfall.
Three of my favourites ornamental grasses are blue fescue, blue oatgrass and Karl Foerster feather reedgrass. While all different, they have the common feature of being well-behaved, non-invasive, bunch (i.e. clump-forming) grasses.
Starting with the shortest of the three, blue fescue (Festuca glauca) reaches four to 10 inches tall and wide, depending on cultivar. Seed heads add an additional few inches, to reach about 10 to 12 inches. Plants start out light green in the spring but by mid-summer the narrow spiky leaves take on a distinctly blue hue. Grows best in full sun to light shade, blue fescue is drought and heat tolerant. It does not like wet conditions and will eventually die out if keep too moist. Elijah Blue is a dependable powder-blue cultivar.
Blue oatgrass (Helictotrichon sempervirens) is a mid-sized grass, 20 to 24 inches tall and wide. The slightly arching seed heads overtop the foliage, often double the height of the foliage to a maximum height of 30 to 40 inches. The leaves are broader than the blue fescue, about 1/4 inch wide. The leaves are also more supple, arching over almost to the ground causing the mound to resemble a small intensely blue fountain. I have several plants in my yard in full sun to part shade, all thriving. As a rule, they prefer well-drained and moist soil. That said, once established blue oatgrass is considered drought-tolerant.
Karl Foerster feather reedgrass (Calamagrostis x acutiflora Karl Foerster) is truly a showstopper in most landscapes because of its height and strong vertical lines. It can reach three to four feet tall by 1.5 to 2.5 feet wide, depending on moisture conditions (i.e. wetter = taller), with plumes of feathery seed heads reaching as high as five to seven feet under ideal conditions. The seeds are sterile, so it will never become a weed problem. The heads make an excellent addition to both fresh and dried arrangements. Leaves are about 1/2 inch wide and dark green. Karl Foerster is an adaptable perennial, able to grow in bog gardens but also equally tolerates heavy clay (thrives in fact) to dry sandy conditions. Plant in full sun to part shade. Because of its broad appeal and versatility, Karl Foerster was the 2001 Perennial Plant of the Year (www.perennialplant.org). Overdam feather reedgrass is a similar cultivar excepting shorter and more compact with variegated foliage.
- This column is provided courtesy of the Saskatchewan Perennial Society (www.saskperennial.ca; email: [email protected]).
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