Ornamental grasses dazzle in late-summer gardens
To everything there is a season, and right now we are in the ornamental grass season. If you look around town, annuals and perennials (the ones that are left after the early September cold snap) are starting to look ragged and tired, but many ornamental grasses are coming into their full glory.
In the world of grasses, there are warm season and cool season species. The name says it all: cool season grasses do most of their growing in spring and fall when temperatures are cool and many go dormant during the hotter months. Warm season grasses wait until soil and air temperatures are warmer and do most of their growing in the summer months. These are the ones that are looking particularly good right now. They have reached maturity, are blooming and starting to form seed heads and are putting on a spectacular show. They range from ethereal, to stout and robust. They come in all colors, from dark and bluish green to reddish and purple hues. Many of the species that you might be seeing now are native to Colorado and therefore cold hardy and drought tolerant. Some of these include the following:
Switchgrass (Panicum virgatum) is a sturdy, drought tolerant species with gorgeous wispy flower heads. There are several cultivars available including ‘Northwind’ which turns a dazzling gold in the fall; ‘Shenandoah’ which goes from green in the spring to deep maroon in the fall; ‘Thundercloud’ has light pink flowers that look like a puffy cloud above the green leaves. These range in height from 4-6’ high.
Blue grama ‘Blonde Ambition’ ( Bouteloua gracilis) is a longtime favorite among many. It is a cultivar of our native state grass of Colorado. Growing much larger that the straight species, it forms a nice airy clump up to 36” tall and wide. The light-colored, horizontal seed heads that resemble eyelashes sit atop blue green foliage and give this grass it’s distinctive look. The whole plant turns a light golden color that persists throughout the winter.
Little bluestem ( Schizachyrium scoparium) is a robust bunch grass that grows 2-3’ tall and has several cultivars. ‘The Blues’ emerges with blue-green leaves that turn to purple in the fall and deep gold in winter; ‘Standing Ovation’ moves from blue to rusty orange in the fall. Each has similar delicate, fluffy seed heads that give great winter interest. Little bluestem provides seeds for birds and is beneficial for several species of butterfly.
Alkali sacaton ( Sporobolus airoides) is a large grass growing up to 5’ tall. It has fine textured leaves and showy, airy flowers and seed heads. You might have guessed from the name, it handles our alkaline soils just fine.
Beyond providing beauty in the landscape during the growing season, grasses (warm and cool season) are workhorses all year round. They can be used to create form and structure in a garden design, they work as accent plants mixed in with perennials and tall species work great as screens. Leave your grasses up through the cold months and they will provide excellent winter interest and even shelter and food for wildlife. I highly recommend you add them to your list for next year, or if you act fast, there is still a short window to plant this season.
After a hot dry summer, it’s nice to see these grasses putting on their show and ushering us into the fall season.
For more information on ornamental grasses visit online: extension.colostate.edu/topicareas/yard-garden/ornamentalgrasses-7-232 and cmg.extension. colostate.edu/gardennotes/
581.pdf.
Deryn Davidson is an Extension Agent – Horticulture at Colorado State University Extension Boulder County. For more information contact CSU Extension at the Boulder County Fairgrounds, 9595 Nelson Road, Box B, Longmont, 303.678.6386, e-mail ddavidson@bouldercounty.org or visit boulder.extension.colostate.edu.