Growing ornamental home landscape grasses in Minnesota

The purpose of this article is to present information on the growing characteristics of certain ornamental landscape grasses that I have successfully grown on a small home landscape plot in Red Wing, MN. While this location is in USDA plant hardiness zone 4a, this zone also now includes most of the south metro area of Minneapolis/St. Paul. The grasses listed here are known to be hardy in the next northerly zone - 3b, which together with zones 4a and 4b, includes all but the northern parts of the state.

The plants to be covered here are:

Blue-eyed Grass - Sisyrinchium bermudianum

Blue Oat Grass - Helictotrichon sempervirens

Fall Blooming Reedgrass - Calamagrostis brachytricha

Feather Reedgrass - Calamagrostis xacutiflora

Hakone Grass - Hakonechloa macra

Miscanthus sinensis 'Graziella'

Palm Sedge - Carex muskingumensis

Purple moorgrass - Molina caerulea

Red Flame Grass - Miscanthus 'Purpurascens'

Switchgrass - Panicum virgatum

Things you need to know about grasses:

Cool or warm season - i.e. when does the plant grow and flower

Culture and maintenance - when to plant and prune, pests

Invasiveness - none of the plants listed here are invasive.

Landscape space - how large to they grow

Sun or shade - most grasses require full sun (but see my notes).

Transplanting and dividing

Water requirements - drought tolerant or not.

I will cover these topics in the discussion of each specific plant. See the bottom of the page for reference information.

Blue-eyed Grass - Sisyrinchium bermudianum

There are a number of species of Blue-eyed grass. This little jewel here, has the same leaf structure as the common blue-eyed grass, S. montanum. It only grows to about a foot in height and thus is more of a border specimen. It will flower from early June until frost if it has enough moisture. While the grass is drought tolerant and can be used in rock gardens, the flowers will be produced all season only if the plant has adequate moisture, otherwise you have early summer flowers only.

Because of its size, you need to be careful that it does not become hidden under over-growing foliage of taller plants. These plants have grown well with only half day sun. They do not have deep roots and thus transplant easily. The specimen pictured here was divided and transplanted the previous summer.

Blue Oat Grass - Helictotrichon sempervirens "Sapphire"

Blue Oat Grass is a cool season grass, meaning it will start growth early in the season before summer heat arrives. The foliage is usually a silvery blue color and of thin spiky leaves. It forms a nice clump with the foliage cascading outward as the photo shows. It works best in average to dry soils that are well drained. In heavy soil, don't over water. The foliage color is the point, it does not produce a flower stem in Minnesota. However it does retain it's color year-round as the species name, sempervirens, (evergreen) indicates.

I have not tried dividing and transplanting. This specimen is four years old and looks great. Unlike most ornamental grasses, you do not cut back the old foliage in the spring. I made the mistake of doing that once and it was a pretty sorry looking plant until mid summer. A large number of the old blades will turn brown over winter, but in the spring, simple comb them out with your hand. You will need to do this several times as they loosen from the base, but the plant will retain it's vigor in this manner.

Palm Sedge - Carex muskingumensis

Palm sedge in normally a plant that is native to moist areas as in marshes, river banks, etc, but I have found it to be a very nice landscape specimen no where near water. This particular plant gets about six hours of sun at the height of summer and does very well if I don't allow it to go more than a week without a drink, otherwise the foliage and flower stems will start to sprawl. This is a cool season plant, so growth takes off early with the flowering stems shooting up above the leaf blades by mid summer. The flower heads somewhat resemble oats or wheat.

The plant grows to 24" to 30" high to the tips of the seed heads, which are quite sturdy if the plant has enough moisture. It stays in a clump that grows outward slowly. As it needs sun, don't let the short leaf stems get hidden by another plant. It is not bothered by any pests.

(muskingumensis = mus-kin-goo-MEN-sis)

The foliage will turn a nice yellow in the fall before becoming the brown color you see here. The seed heads will remain for some winter interest. Like most grasses, do not trim back the old foliage until spring. Mulch a new plant the first winter.

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Purple moorgrass - Molina caerulea 'Variegata'

When you look at the photo of Purple Moorgrass, it belies it's species name which means "dark blue", but the 'Variegata' variety has a bright yellow-green foliage that is particularly attractive when planted in a group of clumps. It is a cool season grass, with nice growth early in the season and the flower stems holding off till the mid summer heats lets up. I have recently transplanted all of these plants as they were being severely hampered by a large mound of Hakone grass. They do not have deep roots and transplant and divide easily. The first season after transplant they didn't look very vigorous but in the second season after transplanting they have filled out nicely.

The plant should get to 30" in height in full sun, but my plants only get about 5 hours at most so they will never get that large, but they do grow nicely. The flower stems are thin and rise above the foliage with tiny yellow flowers. Some of the leaves will retain their color over winter so wait in the spring for growth to occur to see which leaves to trim off. They do not spread much and growth of the base mound of the clump seems to get a little taller each year.

Red Flame Grass - Miscanthus 'Purpurascens'

This grass is a member of the Miscanthus genus which is composed of numerous species and varieties from which to chose for landscape interest. A number of them however, require quite specific selection criteria either due to size, behavior, invasiveness, etc. Red Flame Grass is an excellent selection for the home landscape

It does not self seed, it grows in a nice clump but the clump can spread outward in good growing circumstances and you can have quite a large plant as shown above after four years of growth. Give them room.

The plant is not tolerant of drought, so it needs water about once a week for the best growth and full sun if possible but these specimens here only get about 6 hours maximum in mid summer, so they will grow nicely without full day sun - just don't grow them in the shade. With too little sun or water the stems will lodge. They can be divided and transplanted but be prepared for a chore. The clump is dense and the roots are deep. You will never dig deep enough to get all the roots, so go as deep as you can. My experience is that going down a foot is sufficient. You can cut through the clump with a knife or more likely your shovel. One large clump can provide a number of transplants. Be sure your planting hole has the soil loosened wider and deeper than the transplant will be set.

Like most ornamental grasses, do not cut back the old foliage until the following spring just before new growth starts.

Hakone Grass has become my favorite grass among those presented in this article. As the name implies this is a native of the Hakone (Hah-koh-neh) area of Japan where it grows in moist mountainous woods. It is a warm season grass which means it begins growth slowly in the spring, waiting for the warm weather of Summer to really take off. Hakonechloa (hah-koh-neh-KLOH-ah) is even a little slower than most warm season grasses. We once thought the plants were dying out before we came to realize that it takes a while in the Spring for those first green shoots to come up.

By Summer the plants are really growing. The foliage is soft with some yellowish tinges and becomes weeping as you can see above as it grows and grows, but it never lodges - the stems hold up nicely even after a heavy rain.

In late Summer the flower heads come out and are more yellowish than greenish. They appear like soft brushes and have a weeping appearance just like the stems. In October the color begins to change taking on a golden color and if the Autumn is just right for temperature and the snow holds off you can get the almost orange color shown in the photo. The gold coloration always comes but in 2009 the Autumn was just right for the darker colors to come out.

The Minnesota Landscape Arboretum grew their experimental plot of Hakonechloa in shade and light to heavy shade is recommended for the grass, however, with the "All Gold" variety I have found that it needs some sun. A plant in light shade all day does not do well. This group of plants gets about 4 to 5 hours of direct sunlight on a summer day. Less in fall.

This planting consists of only six plants. It is now 12 feet wide but has taken five summers to reach this size. Each year it is more beautiful. The plants are spaced about 1-1/2" feet apart and as shown, they lean outward toward the open space. The base clump does not grow outward very rapidly and the inside of the clump does not seem to die off as some grass clumps will do. The height is about 18". Like most ornamental grasses, do not cut off the old growth until the following spring. The grass expert at the Minnesota Landscape Arboretum questioned whether Hakonechloa was hardy enough for our area, but it certainly seems to be. Young plants should certainly be mulched the first few winters.

In the photos at right we have a progression from bottom to top of early September, early November and early December.

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I first planted this variety in 2007 and had to move them in the spring of 2008. These can become large - definitely a background plant, but quite interesting. The stems are quite stiff and the leaves stiff. This is a warm season grass, so growth is slow in the spring. I can give them about five hours a day of sunlight and they probably should have more, as the flower stems only emerge in September and the seed head unfolds later, but if the weather is good you will have some magnificent flower heads.

“Graziella” means graceful, and the seed heads are definitely that - very showy with good contrasting color between the stem and seed head. In full sun, they would definitely mature a little earlier. This plant needs space. The foliage on a plant with a one foot diameter clump will spread six feet at the top - it somewhat resembles a fountain - contrast that with the ‘Northwind’ Switchgrass which is almost straight upright.

Plant them where you want them because moving them is a chore. They will tend to grow outward from the center of the clump and the center may not show growth as the years go by, however, the plant is expected to live for 5 to 10 years, but if you live in USDA hardiness zone 3, you should mulch these plants each winter as Zone 4 is preferred. Always winter mulch a new plant or a transplant. Cut the old stems only in the spring of the following year.

Switchgrass is a native grass of the tall grass prairie. The native varieties are aggressive and they self-seed. The cultivars that have been tested at the Minnesota Landscape Arboretum are much better behaved. All are warm season grasses, meaning that growth is slow in the spring until the days really warm up. Because these cultivars are derived from sturdy native stock, they hold up extremely well in the home landscape. Further the seeds produced are attractive to birds but the seeds do not self-seed.

I have only grown two cultivars - ‘Northwind’ and 'Prairie Sky'. 'Northwind' is an outstanding grass. It can reach from 3 to 6 feet in height, needs good sun, at least 5 hours per day for a good plant, tolerates average soil. ‘Northwind’ grows very upright, no sprawling or lodging in hot or rainy weather. (Some of the cultivars available will sprawl by mid-summer - ‘Prairie Sky’ particularly. The flower heads appear only in late summer on sturdy stems. This is a plant to provide a good tall backdrop, support to weaker specimens, and winter interest. The plants can become quite large so give them some room and if you need to divide or move them see my notes up under Feather Reed Grass.