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With only a little foresight and planning, the fall perennial garden can offer as much color and excitement as the spring or summer garden. Black-eyed Susan, coneflower, stonecrop, Japanese anemone, asters and mums are traditional fall blooming perennials that we've come to depend on. Yet, ornamental grasses add a special beauty to the late season garden in ways other perennials can not match.
Grasses contrast with traditional perennial plants through texture, form, color, and movement. Use them as an accent plant, a specimen plant, a screen or natural fence, or in a transitional area between formal and wilder areas of a garden. Many grasses are excellent near water, or in container and rock gardens. Cut the flowers and foliage for use in fresh or dried flower bouquets or for crafts. Mature seeds provide necessary winter food for birds and other wildlife. Ornamental grasses can be used as the structural "backbone" of a perennial garden much like shrubs, trees, and hard scape (fences, trellises, arbors, and walls.)
Grasses are grouped according to their growth habit. Most ornamental grasses offered by area garden centers are bunch grasses. Forming a distinct clump, bunch grasses increase in size over the years by lateral branches or tillers. Bunch grasses differ in shape depending on the species. Vase-shaped, mounded, arching, and tufted forms provide contrast to sprawling asters, mounded mums, and upright coneflowers. The second group, sod-forming grasses, form a dense mat by producing underground stems (rhizomes) or above ground stems (stolons.) Many of these grasses are used as a ground cover.
Ornamental grasses are also grouped according to their season of active growth. Cool-season grasses begin growth in late winter and early spring, becoming dormant in the heat of the summer. They flower before dormancy. Cool-season grasses resume growth in the fall. Generally, this group requires more moisture than warm-season grasses. Fescues (Festuca spp.) are an example of this type of grass.
Warm-season grasses such as Maiden Hair (Miscanthus spp.) begin growth in spring and require the heat of summer to mature. Flowering occurs in summer, fall, or not at all, if the summer season is too cool or short. Winter is their dormant period. Many warm-season grasses change colors in the fall. The oranges, reds, and purples of their foliage is as showy as the deciduous trees. In winter, the foliage bleaches to rich tans and golden-browns, remaining colorful against the otherwise bare ground of a dormant perennial garden. Flower stalks and mounds of foliage add form and movement as effectively as shrubs and trees in the winter landscape.
Ornamental grasses are easy to grow and relatively pest free. Care includes a late winter "haircut" before new growth begins and periodic division when the clump overgrows its spot or begins to die out in the center. When planting grass, be careful to match the original soil line, planting neither too deep nor too shallow. Water immediately and monitor moisture levels until established. Young grass plants shouldn't dry out, although many varieties are quite drought tolerant later on. Mulch to keep down weeds and cool the soil surface. Most grasses require full sun. Variegated varieties tend to burn in a southern exposure and do well in light shade.
There are many wonderful varieties of grass to choose from. For excellent fall and winter ornamental features the following are suggested:
Switch grass (Panicum virgatum) - A North American prairie native, this warm-season, bunch grass has soft gray-green leaves that turn golden in the fall. Flowering begins mid-summer. The flower stalks are open, airy, and persist into winter. Try the cultivar ‘Rotstrahlbusch' for excellent red fall color.
Big bluestem, turkey foot (Andropogon gerardii) - Another prairie native, big bluestem has purplish blooms shaped like a turkey foot. It is a warm-season bunch grass of upright form reaching 4-5 ft. tall. The blue-green foliage turns shades of coppery red and purple in the fall.
Fountain grass (Pennisetum alopecuroides) - Fountain grass reaches 2-3 ft. tall, although there are many fine cultivars that are shorter. The blooms resemble foxtails, range from creamy-white to pinkish-tan, and remain attractive into fall. The fall foliage color is golden-yellow.
Maiden grass, Eulalia (Miscanthus sinensis cultivars)- There are so many excellent cultivars of maiden grass that it would be impossible to describe them all. A warm-season bunch grass, maiden grass has the stature and attractiveness needed for a specimen plant. The flowers and fall foliage color varies depending on the cultivar.
Karl Foerster feather reed grass (Calamagrostis x acutiflora [Karl Foerster]) - This cultivar is the best known feather reed grass. It is a cool-season grass with an upright form. It blooms mid- summer. The vertical flower stalks mature to a tawny gold and remain showy into the winter.
Little bluestem (Schizachyrium scoparium) - This warm-season bunch grass is finer in texture than big bluestem and not as tall. It blooms in late summer. The flowers are not as showy as other grasses but are beautiful when back-lit by the winter sun. The fall color, a combination of reds, purples, and oranges, can't be beat!
Q: I have prepared a new flower bed. My goal is to design a permanent perennial garden this winter for spring planting. Are there any annuals I can plant now that will brighten this area for fall?
A: There are several annuals or tender perennials that can be used even in the fall to add color until prolonged cold temperatures end the show. Frost tolerant choices include pot marigold Calendula officinalis, flowering tobacco Nicotiana alata, pansy, annual phlox Phlox drummondii, mealy-cup sage Salvia farinacea, Autumn sage Salvia greggii, Verbena canadensis, and stock Matthiola incana. These plants can tolerate temperatures that dip into the upper 20's. Frost hardy choices include alyssum, wallflower Cherianthus, China pinks Dianthus chinensis, dusty miller, flowering kale and cabbage, pansies, violas, and snapdragons. These traditional bedding plants can withstand periodic dips in temperature to 20 degrees F. Depending on the site, pansies, violas, dusty miller, snapdragons and China pinks have been known to overwinter successfully along the Front Range. Add fall mums in autumn colors to complete the bed.
Q: I have a large lot with many trees and shrubs. What can I prune now and what should I leave for the spring?
A: As a rule of thumb, deciduous trees are best pruned when dormant. After the leaves drop, it is easier to see the natural structure of the tree. You can begin pruning in late fall or leave it for the nice sunny days of late winter and early spring before bud break. Remove crossing limbs or those with poor branch angles first before making any cuts to shape or thin. Broken, dead and diseased limbs should be pruned out immediately regardless of the season. Pine trees should be pruned in the spring by twisting off a portion of the new growth when in the "candle stage." Junipers and spruce can be pruned at anytime except when the temperatures are excessively cold. Spring blooming shrubs should be pruned after they have finished blooming. Summer and fall blooming shrubs can be cut back in late winter or early spring.
Q: How can I keep insects and spiders from invading my home this fall?
A: There are a few preparations you can do that will decrease the numbers of critters hiding out in your home. First remove debris from around your foundation, especially from under foundation landscaping. Leaf litter, grass, twigs, etc. provide cover, food, and a nesting place. By removing these, you will discourage habitation close to the home. Next, caulk any foundation and window cracks that could be used as an entry. Scout your home periodically and use the vacuum to clean up webs and remove dust, lint, and animal hair that make good nesting material.
Powdery Mildew
If powdery mildew is a problem, avoid late-summer applications of nitrogen
fertilizer to limit the new tissue growth, which is more susceptible to
infection. Remove and throw away (do not compost) infected plant
parts as soon as possible. This decreases the ability of the fungus to
survive the winter. Thin out plants if possible to increase air flow through
the plants and minimize humidity by using a drip irrigation system rather
than overhead.
Reduce Watering
Back off on watering trees, shrubs, vines, hedges, roses and perennial
vegetables, such as rhubarb and asparagus. This lack of water will begin
the hardening off process that takes place in the cells of the plant and
prepares the plant for winter. Water again in late fall and winter if the
weather is dry and with very little snow cover.
The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.
Fact Sheets are available at the Larimer County Extension Office, 1525 Blue Spruce Drive, Fort Collins, Colorado, telephone (970) 498-6000, or contact us by e-mail at larimer@coop.ext.colostate.edu
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