By Silvia Strobl, Master Gardener

This week I’ve been enjoying watching a flock of American Tree Sparrows that have migrated south from their summer tundra breeding grounds to my garden north of Peterborough for the winter. While I have both sunflower and nyger feeders, they are feeding exclusively on the Big Bluestem and Savannah Grass seeds in my garden. Sadly, these native grasses seem to have a bad rap among gardeners which is too bad as they have many benefits for both you and local wildlife.

I have the following four commonly occurring warm season perennial native grasses in my full sun garden:

Big Bluestem (Andropogon gerardii) is a very tall (5 – 8 ft) grass with clumps that form a dense sod but does not creep by rhizomes. It competes aggressively with shallow-rooted flowers, so it is best planted with species that form deep tap roots or spring bloomers that go dormant in the summer. In my garden it is a fall season focal point at the back of a border behind Culver’s Root (Veronicastrum virginicum) which has a central taproot as well as underground rhizomes.

Little Bluestem (Schizachyrium scoparium) is an excellent grass for gardens due to its shorter height (2 – 4 ft), clumping form, very showy silver-white seed heads, and bright red stems in fall.It prefers dry sandy soils.

Savannah Grass (Sorghastrum nutans)is another tall grass (5 -7 ft) for the back of the border. It tends to self-sow so the young seedlings require a little annual weeding.

Native grasses add movement and colour to the garden. Little Bluestem’s red stems are illuminated by early October morning sun (left) while the late afternoon August sun highlights the tiny golden flowers and flower stalks of Savannah Grass (right).

Sideoats Grama (Bouteloua curtipendula) is a hardy, short bunchgrass that spreads very slowly by means of short, stout rhizomes and doesn’t compete with other plants. Its deep fibrous roots make it useful on slopes to prevent erosion (or on the edges of slightly sloped garden beds as in my garden). Do not plant it in clay soils.

Sideoats Grama has delicate hanging flowers (left), and later seeds (right) that are held in spikes that fall gracefully to one side of the stem.

Benefits for you

As well as being stunning fall and winter focal points, the tall native grasses, Big Bluestem and Savannah Grass, make excellent privacy borders. Their very deep roots (5-6 feet or more) make them useful for erosion control on slopes. Each of these native grasses is drought tolerant. And, each creates excellent winter interest as they tend to maintain their upright form. Another bonus is that they all have low palatability to deer.

Big Bluestem (left) and Savannah Grass (right) stand tall in the author’s garden despite 12 inches of winter snow.

Benefits for wildlife

Many butterfly skipper and moth larvae feed on these native grasses and they provide critically important seeds and habitat for native birds in fall and winter.

An adult Delaware Skipper rests on a blade of Big Bluestem in the author’s garden (left). Big Bluestem is a host plant for this butterfly’s larvae. Both Little Bluestem and Sideoats Grama are host plants for Leonard’s Skipper caterpillars. The adult butterfly is seen here nectaring on marigold in the author’s garden (right)

American Tree Sparrows feeding on a buffet of Big Bluestem (left) and Savannah Grass (right) seeds in the author’s garden. It is fun to watch them “ride” the Savannah grass stems to the ground so they can more easily peck at the seeds some of which spill onto the fresh snow.

Native Grass Establishment and Maintenance

Most native plant nurseries stock these grasses and all of them are easily propagated from seed. Plant seedlings densely at 1 ft to 1.5 ft spacing to discourage weeds. Water during the first year while roots are getting established. Fertilization is not necessary. All can be easily divided, but Sideoats Grama should be teased apart, not cut with a spade.

Remnant pockets of native grasses like this one of Big Bluestem growing on the shoreline of Little Jack Lake (left) are good places to collect seeds to propagate your own plants (right). Never collect more than 10% of seeds.

Depending on how much seed the birds eat in winter, you might get a few volunteer seedlings. If you don’t want more plants, they are easily kept in check by weeding when they are small.

If weedy cool season grasses have seeded into native warm season clumps, use a propane torch in early spring to burn emerged leaf blades while warm season native grasses are still dormant. Be sure to first cut off last year’s dry stalks and have a hose nearby. Don’t do this on a windy day!

Big Bluestem, Savannah and Little Bluestem are 3 of the 4 dominant grasses found in remnant tall grass prairies and oak savannahs, of which less than 1% of their pre-European settlement extent remains in Ontario. (The other is Switchgrass (Panicum virgatum) which can self sow quite a bit so might not be suitable for small gardens.) These grasses are also found on dunes, sandy shorelines, rock barrens, roadsides, and hydro corridors. Including these grasses in your garden can help support some of the wildlife that rely on this endangered ecosystem.

REFERENCES & ADDITIONAL RESOURCES

Diboll, N and H. Cox. 2023. The Gardener’s Guide to Prairie Plants. Pages 302-303, 306-307, 326-329.

Ehrlich, P. R. D.S. Dobkin and D. Wehte. 1988. The Birder’s Handbook A Field Guide to the Natural History of North American Birds, The Essential Companion to your Identification Guide. Page 584.

Johnson, L. and S. Colla. 2022. A Garden for the Rusty-Patched Bumblebee—Creating Habitat for Native Pollinators. Pages 149, 150, and 159.

Map of Native Plant Nurseries in Ontario maintained by Halton & Area Master  Gardeners

North American Native Plant Society. 2017. Seed collecting and saving.

RELATED

GARDENING FOR BIRDS THROUGH THE SEASONS

A FEW OF MY FAVOURITE NATIVE PLANTS

EXPANDING YOUR NATIVE PLANT PALETTE

WINTER FAVOURITES