Whether you grow them for their showy seedheads or their fall foliage, ornamental grasses bring a welcome shot of drama to the autumn garden.
Ornamental grasses add texture and movement to gardens throughout much of the year, but autumn is when so many of the grasses come into their glory.
The seedheads (which develop after the blooms) provide interest through fall and well into winter. And some grasses even flaunt gold, orange, or burgundy foliage for a month or more.
These ornamental grasses mix beautifully with fall-blooming perennials such as asters, goldenrod, mums and sedums.
And you can showcase fluffy seedheads and colorful leaves by placing grasses in a spot where they'll catch late-day sun. In fall, the rapidly diminishing angle of the sun brings light through leaves, making fall-colored grass glow like a wildfire. So even if you won't be planting ornamental grasses until next spring, select some sunlit spots in your yard this fall.
CHOICE GRASSES FOR MINNESOTA GARDENS
FLOWERS AND SEEDHEADS
'Karl Foerster' feather reed grass
(Calamagrostis x acutiflora 'Karl Foerster')
'Karl Foerster' feather reed grass makes an extended presence in the garden: Its airy, midsummer blooms are followed by upright, wheatlike seedheads that accent fall gardens and persist into winter.
Fall-blooming feather reed grass
Although it starts as an innocuous mound of green foliage in the summer, fall-blooming feather reed grass suddenly blossoms in September. The airy, pinkish, bottle-brush flowerheads glow in the autumn sunlight and pair well with 'Autumn Joy' and other fall sedums.
Japanese silver grass
This species has led the interest in ornamental grasses. Blooming from late summer through fall, all cultivars of Japanese silver grass bear showy silver-white seed plumes from fall into winter. There's great variability in hardiness, though, so before you buy, consult a good reference book, such as "Ornamental Grasses for Cold Climates" (University of Minnesota, $9.95) to choose a cultivar that's hardy here.
Be sure to avoid the related species Miscanthus sacchariflorus (also known as silver banner grass). It's an aggressive spreader that can invade native grasslands.
This native grass species has wildly variable form, so selected cultivars are the best bet for gardens. The airy, white-to-pinkish flower heads form in late summer and early fall. The tan seedheads persist into winter and provide a good seed source for birds. Good cultivars include 'Heavy Metal,' 'Northwind,' 'Shenandoah' and 'Rotstrahlbusch.'
Not the best choice for small gardens, but for those who have room for a bit of prairie this is one of the dominant grass species. This towering (6 to 8 feet) native produces distinctive, purplish flowers and seed heads that take the shape of a turkey's foot.
Northern sea oats
Though marginally hardy in Zone 4, northern sea oats is worth trying for its unique seedheads, which look like flattened wheat or oat seedheads and change from pale green to pink-bronze in fall. Cut the stems for long-lasting dried bouquets.
GRASSES FOR FALL FOLIAGE
The foliage of this native prairie grass often develops rich orange, red and burgundy tints in the fall. For reliable, outstanding red-purple fall color, try Blue Heaven, a recent introduction from the University of Minnesota.
This hybrid Miscanthus is very hardy (to Zone 3) and develops nice orange and red foliage highlights in the fall. It's also sterile, so there's not a threat of unwanted seeding.
This native prairie grass has delicate, mounded foliage that often turns warm yellow to pale orange in autumn. Another great fall feature is its airy, fragrant fall seedheads, which catch the light beautifully.
Nancy Rose is a horticulturist with the University of Minnesota Extension. To ask her a gardening question, call 612-673-9073 and leave a message. She will answer questions in this column only.