By Jan Midgley
In dry lands with few woody plants, grasses are the foundation of the landscape both functionally and aesthetically. But why should we include them in public and private designed landscapes? The small, wind pollinated flowers are not as showy as the flowers of forbs (flowering herbaceous plants that are not a graminoid (grass, sedge, rush)). The visual beauty of grasses lies in their structure, texture and color.
Throughout the year, native grasses provide the same invaluable ecological services in man made landscapes as in natural areas. They provide food and shelter for birds, insects and wildlife in general. As host plants for lepidoptera, grasses sustain insect larvae so essential for baby birds. Grasses have low water requirements after the first year of establishment and stabilize the soil. Grasses contribute to carbon capture, and the deep, extensive root systems aid in soil development. The western prairies provided rich land to plow for crops because the dance of plants and animals had continued for millennia. Introducing graminoids into soils that have been impacted by agriculture and development helps to rebuild those soils and restore food webs.
Grasses can be used as the matrix for a mixed prairie, for borders and as accent plants. The native grasses discussed in this article are perennials. They may be low and turf forming or provide tall vertical elements. Texture choices range from fine to coarse. A grass might serve as a bushy anchor or an airy clump to soften a hard landscape edge. The foliage responds to wind, which adds motion to the landscape.
The small flowers and the prominent stamens have lively colors on close view, but the most lasting color is in the leaves. Colors range from bright to gray greens to blues to reds. Some, like the Schizachyrium scoparium (Little Bluestem), change color over time. Early in the season, the stem internodes may alternate green and red and eventually the entire clump shines red gold when backlit with western light.
All grasses offer winter beauty. Locate clumps to allow the low angle of winter light to pass through the seed heads. Morning and more importantly late afternoon light highlight the seeds. In the evening, the inflorescence of Sorghastrum nutans (Indian Grass) resembles a candle flame. Snow may crush smaller, delicate blades, but overall the landscape is enhanced by clumps of grass skirted with snow and sparkles of ice.
Native grasses have varying water needs. Grasses that evolved in the short grass prairie have the lowest water needs. Mixed grass prairie species are just that, a mix. Tall grass prairie species need slightly more water. None of them are thirsty garden plants, partially because they have such extensive root systems. The narrow leaves help prevent water loss, and grasses’ special methods of photosynthesis help regulate water needs.
Grasses have stomata or pores on their leaves through which they let gasses and water enter or leave. The dumbbell shaped cells on each side of the stomata of grasses differ from the cell shape alongside pores on forbs. Grasses can open and close their stomata more quickly and thus lose less water during gas exchange.
Cool and Warm Season Native Grasses
Native grasses are separated into two groups called cool season and warm season. The most important difference between these two groups is their time of active growth. Cool season grasses grow actively in cooler temperatures. They flower and develop seeds before the hotter longer days of summer and fall. Warm season grasses grow actively during the warmest months.
These groups are often labeled C3 and C4 grasses. A big majority of plants on the planet (85%) are cool season (C3) plants. They have one type of cell and one type of enzyme in their leaves to conduct photosynthesis. They take in carbon dioxide and an enzyme assists in conversion of the CO2 into a 3 carbon compound. Warm season (C4) plants have two types of cells and two types of enzymes to convert CO2 into a 4 carbon compound. Cool season plants use less energy and create high quality forage but in low quantity. The warm season grasses use a bit more energy in their photosynthetic process, but the output of carbohydrates and plant mass is much greater.
When temperatures rise, cool season grasses open their stomata widely in the daytime to allow more CO2 to enter their tissues. Once the temperature rises above a certain level, they begin to lose excess water through the stomata. In the absence of extra moisture, they go dormant.
Landscapers and gardeners can take advantage of the differences in cool season and warm season grasses. We think of grasses as sun plants, but some cool season grasses are shade tolerant. In addition to lower light requirements, they also have lower temperature requirements and are less sensitive to frost. They might need a bit more water than warm season grasses in the heat of summer if you want to stave off dormancy. Cool season grasses are often well suited to higher elevations. See the Cool and Warm Season Colorado Native Grasses Chart for details about individual species.
Examples of cool season grasses:
- Ericoma hymenoides (Indian Ricegrass)
- Elymus canadensis (Canada Wild Rye)
- Elymus elymoides (Squirreltail Bottlebrush)
- Festuca arizonica (Arizona Fescue)
- Festuca idahoensis (Idaho Fescue, Blue Bunchgrass)
- Hesperostipa comata (Needle & Thread)
- Koeleria macrantha (Junegrass)
- Nassella viridula (Green Needlegrass)
- Pascopyrum smithii (Western Wheatgrass)
“I’ve really enjoyed Festuca arizonica around The Gardens here. It performs well in an array of lighting situations and moisture regimes, is native to the region, and has a clean, fine-textured, attractive look almost all the time! It is a cool season grower…It’s long-lived and tough but mild-mannered in our landscapes here.” email, 2/22/21, Bryan Fischer, Horticulturist at the Gardens on Spring Creek, Fort Collins, CO.
Warm season grasses shine during the heat of summer and fall. They offer winter structure to the garden and food for birds.
Examples of warm season grasses:
- Andropogon hallii (Sand Bluestem)
- Bouteloua curtipendula (Sideoats Grama)
- Bouteloua gracilis (Blue Grama)
- Buchloe dactyloides (Buffalo Grass)
- Hilaria jamesii (Galleta)
- Muhlenbergia montana (Mountain Muhly)
- Muhlenbergia pungens (Sandhill Muhly)
- Panicum virgatum (Switchgrass)
- Schizachyrium scoparium (Common Little Bluestem)
- Sorghastrum nutans (Yellow Indiangrass)
- Sporobolus airoides (Alkali Sacaton)
- Sporobolis giganteus (Giant Dropseed)
- Sporobolis heterolepsis (Prairie Dropseed)
Recommended Seed Mix for Colorado Shortgrass Prairie
The Lady Bird Johnson Wildflower Center recommends a combination of Bouteloua gracilis, Buchloe dactyloides and Hilaria jamesii as a seed mix for Colorado in areas that would have once been short grass prairie. This includes a large swathe of land east of the Foothills and out to the Plains. The area is drier than the tall grass prairie, which ranges farther east.
Bouteloua gracilis (Blue Grama), our state grass, is wide ranging (3500-10,000’) and maintains a graceful, fine textured 1-2 feet presence. The flowers hang on one side of the spike looking every bit like an eyelash. With minimal water it can be a sod former. If conditions are hot and dry, it remains more of a bunch grass. Blue Grama plays well with other perennials.
Buchloe dactyloides (Buffalo Grass) is a stoloniferous ground cover and fills around the other plants. The leaves are pale green to buff tan as the season progresses. It is dioecious, (separate male and female plants) and the two types of inflorescence have different habits. The male flowers form on an erect rachis. The female flowers array along the stolons and gradually turn into a non-piercing bur. Don’t be shocked by the day-glow green of purchased seeds. They are treated with potassium nitrate to oxygenate the embryos. Untreated seeds can take a few years to germinate.
Hilaria jamesii (Galleta) is a bit slow to establish but gradually forms a 2 foot wide clump with a height of 1.5-2 feet. The inflorescence is a two-sided spike. The leaves are a pale blue-gray.
The 3 grasses discussed above can be mowed to a 6 inch height for a more manicured look.
Purchasing and Propagating Colorado Native Grasses
Many species of native grasses are sold as container plants. Some of these may be cultivars. Some may have been treated with neonicotinoids or other chemicals. Grasses do not tend to be plagued by diseases and pests as much as more tender forbs so chemicals may not be as much of an issue when buying grass plants.
Seeds of all of the above mentioned species are available commercially. If you wish to collect seeds from your own garden eventually, it is desirable to have several plants to support wind pollination. Three or more identical cultivars does not count as multiple plants if they have been propagated vegetatively. Those are clones. Growing your own plants from seeds is an inexpensive way to add multiple biodiverse plants.
Avoid seed collection along roadsides. Aside from ownership and safety issues, roadsides may have been seeded with cultivars of grass species that have been selected for robust plants with wide blades. They are often selected for forage for domestic livestock. They can be aggressive and create a monoculture as well as being coarse in appearance when planted in garden situations.
Sow the seeds of cool season grasses mid March to April 1 (60-75˚ highs). Sow warm season grasses from mid April to June (75-90˚ highs). Germination occurs rapidly if the seeds experience big temperature swings from night to day. They can be sown in situ, in cells, or in pots. Cover the seeds lightly. Protect them from birds until they germinate and from rabbits after they germinate. Hardware cloth or inverted lattice flats serve the purpose. Protection is more difficult when seeds are sown in situ. A bit more cover or drilling into the ground may be necessary to foil birds.
Plant the cells or pots of cool season grasses in early to mid May if possible, at least by June 1 in the Front Range. Planting plugs from cells is highly successful. They need some time to get their roots established before the heat of summer sends them into dormancy, which they will not survive without adequate underground structures. Warm season grasses are more forgiving but getting them into the ground by mid June is beneficial.
Save garden clean up for February or March depending on elevation. Watching birds feeding on the seeds of grasses is a favorite winter pastime. A weed whacker can assist in cutting back grasses. Remember the solitary bees who use hollow stalks for nests. Leaving culms about 12-14 inches tall for the bees will not be an eyesore. New leaf growth will soon disguise these bee nurseries.
After two years, gardens of mixed grasses and forbs have established root systems and can tolerate and even benefit from grazing whether the mammal is an ungulate or a rabbit.
Native grasses contribute beauty and habitat to any garden whether formal or naturalized. Use them in borders, perennial beds or in prairie gardens. They provide pleasure year round.
Curious to learn more about transforming your garden into a habitat with Colorado native wildflowers, grasses, shrubs, and trees? Check out our native gardening toolkit, register for an upcoming event, subscribe to our newsletter, and/or become a member – if you’re not one already!