Muhly Grass (Muhlenbergia capillaris)

Gulf Muhly, Hairgrass, Muhly Grass, Mule Grass, Pink Hair Grass, Pink Muhly, Pink Muhly Grass, Purple Muhly

As the garden winds down in late summer and fall, pink muhly grass explodes with airy, pink plumes. This perennial grass is beautiful and easy to grow. Read on for muhly grass care and to learn how to grow ornamental muhly grass. The appeal the plant will give to your garden is well worth the effort.

I. Appearance and Characteristics 

Muhlenbergia capillaris, commonly known as the hairawn muhly, native to eastern North America and can be used for a multitude of purposes, including ornamental gardening and farming. It was voted 2012 plant of the year by the Garden Club of America.

Jean-Baptiste Lamarck described this species in 1791 as Stipa capillaris before it gained its current name from Carl Bernhard von Trinius in 1824.

Individuals of this species are grouped into shrubs of “capillary”-like branching pattern with green leaves covering the understory and pink flowers outgrowing them. The muhly grass is a cespitose perennial that grows to be 30–90 cm (0.98–2.95 ft) tall and 60–90 cm (2.0–3.0 ft) wide. The blades are rolled, flat to involute during maturity and are about 15–35 cm long and 1.3–3.5 mm wide at the base with tapering or filiform tips. The sterns are erect or decumbent at the base of the shrub. The leaves are inflorescence and narrow with a contracted or open panicle of small spikelets, each spikelet being 1-flowered and rarely 2-flowered. The wiry, thin leaves are simple and alternating from the stem; they grow to be about 18–36 inches long. The flowers of the grass are grouped together, forming long, airy clusters along a stem that rises above the leaves to a length of about 18 inches (460 mm) and width of 10 inches (250 mm).

Flowers of M. capillaris are perfect with each having about two or three stamens and anthers that are about 1–1.8 mm long. Spikelets are found on the long, hair-like pedicels that are clavate-thickened at the apex and are slightly scabrous. The glumes are found to be unequal, and are either longer or shorter than the lemma. The lemma is obtuse to acuminate or awned, while the membranous lemma is narrow, acute, mucronate, or awned, and usually pilose at the base. The flowers grow during the fall season, especially from September to October, and are usually colored pink or purplish-red. They mature from the bottom up. The plant is a “warm-season” plant, so it starts growing during the summer and is in full bloom during the autumn. The seed stalks are 60–150 cm (2.0–4.9 ft) tall. The flowers produce oblong tan or brown seeds that are less than half an inch long. The plants grow in clumps, but do not spread through above-ground or underground stems.

Muhlenbergia capillaris can be found in sandy or rocky woods and clearings originating from a range of host states, which include Florida to East Texas, north to Massachusetts, New Jersey, eastern Pennsylvania, Kentucky, southern Indiana, Missouri, and Kansas. However, it is endangered in Connecticut, Indiana, Maryland, and New Jersey, and is said to have vanished from Pennsylvania and almost certainly Ohio. The muhly grows along the border of roads and in plain prairies. The grass clumps into herds, causing bush-like establishments in the area the hairawn muhly inhabits.

II. How to Grow and Care

Sunlight

Pink muhly grass needs to be planted in full to partial sunlight. It can tolerate some shade, but for proper growth and blooming, the grass requires at least six hours of sunlight (or more) each day.

Temperature and Humidity

Pink muhly grass flourishes in warm, dry weather. While it’s native as far north as Massachusetts, it’s often found in abundance in hot, dry climates where it grows well and returns year after year. And while this plant has no problem with warm weather, too much humidity can affect it negatively and might increase susceptibility to tar spot, a fungal plant disease.

This plant is only hardy to USDA cold hardiness zone 6, meaning it can’t tolerate winter temperatures much below minus-10 degrees Fahrenheit without dying off. In such cases, choose a more cold-tolerant, hardy ornamental grass.

Watering

Water as needed to keep the soil moist if rainfall is insufficient. Let the top inch or two of soil dry out before watering again. Muhly grass tolerates drought very well and may not even need watering unless there’s a prolonged dry period. Be careful not to overwater when the plants aren’t actively growing.

Soil

The most important thing to know is that this type of grass requires dry-to-medium, well-draining soil. If the soil becomes too wet or boggy, pink muhly grass will not thrive.

In terms of soil pH, this plant prefers slightly acidic to neutral soils. It does not grow well in alkaline soils with a pH higher than 7.0.

Pink muhly grass tolerates salinity exceptionally well. So soil with elevated salt content due to irrigation, mineral weatherization, or road salt is generally not a problem for growing this type of grass.

Fertilizing

Pink Muhly Grass does not require fertilization, but if your plants are struggling or showing signs of stunted growth, we suggest feeding your plants a balanced, slow-release fertilizer in late winter or early spring. While fertilization is not necessary to grow Muhly Grass successfully, it can help boost the growth rate and vitality of your plants.

Mulching

Adding bark mulch to your newly planted Pink Muhly is ideal. Not only does it hold in just enough moisture, but it also helps fight against invasive weeds. Additionally, it protects the roots during cold winters. This means that you will need to do even less watering. To apply, add 1-2” of mulch a few inches from the root zone of your newly planted seedlings in late fall, before the ground freezes.

Planting Instructions

Wait until all chance of frost has passed in the spring to sow pink muhly grass seeds directly in the garden. If you prefer, sow them in late spring or early summer. In either case, press the seeds into the soil but don’t cover them. Keep the soil moist until the seeds sprout in about 10 to 21 days.

For pink muhly grass plants, dig holes two or three times wider than the root balls and no deeper than the height of the root balls. Put the plants in the holes and add water. After the water soaks in, backfill the holes with native soil mixed with some organic matter. Keep the crown of the plants just above the soil line. Water again and keep the soil evenly moist, not soggy, for the first year. Add an inch or two of mulch to help suppress weeds and retain moisture.

You can also plant pink muhly grass in a container large enough for it to grow in for a couple of years. Be sure the pot has drainage holes. When you repot, in two or three years, use a fresh potting mix.

Pruning

This perennial plant will benefit from being cut back in the late winter or early spring but no later than that and before the growing season begins. Be sure not to cut too close to the crown of the plant—a distance of at least three to four inches should be sufficient.

Avoid pruning this plant in mid-to-late summer because doing so can interfere with the production of the beautiful plumes of flowers for which pink muhly grass is known.

Propagation

Division

A stand of showy pink muhly grass can become a real show-stopping display that can be created by propagation. These plants are relatively easy to propagate by either seed collection or division. In fact, dividing pink muhly grass plants typically becomes necessary every few years to keep them tidy and maintain necessary spacing between individual plants. Otherwise, the plant continues to spread and a dead area can form in the center of the clump. To propagate by division, follow these steps:

  • Using a shovel or spade, dig around the perimeter of an individual plant, and then be sure to dig deep enough under the plant to free the root ball.
  • Split the plant into two or three equal parts, depending on the size of the root ball. Keep in mind that ornamental grasses can have very dense, fibrous root systems. It might take a sharp tool or even a chainsaw to divide the root system. Use caution and wear personal protective equipment.
  • Place one division of the plant back into the original hole. The remaining sections can be relocated or passed along to a friend for planting in their garden.

Seed

Growing pink muhly from seed is easy, but be prepared to wait a season to see blooms after seedlings are transplanted into the ground. To propagate by seed, you’ll need to collect the brown seeds that collect in the flower plumes. Once the brilliant pink or reddish hues have faded from the flowers in late fall, it’s time to collect the seeds. You can comb the plume to release the seeds—leaving the dried flowering grass intact for some visual interest through the winter season. Once you have collected the seeds, follow these simple steps:

  • Plant the seeds in early spring, either indoors or you can directly sow them outside in a sheltered area if the climate is favorable enough.
  • Pink muhly grass seeds need light in order to germinate, so sow them on top of a layer of soil but don’t cover them with soil.
  • Mist with water to maintain moisture until the seeds begin to sprout, which should be in about two weeks.

Weed Control 

Keep weeds removed so your pink grass won’t have to compete for water and nutrients. A layer of mulch will help discourage weeds.

Pests and Diseases

Growing Problems

Over-watering can cause the conditions that enable fungal root rot diseases to form. Since your muhlenbergia capillaris is drought tolerant, it does better with too little water than too much.

Extreme cold conditions can cause the grass to die back. It’ll return in the spring unless there’s an extended period of temperatures below -10° F, at which point the roots will die off as well.

Pests

Your plants won’t experience many pest issues. Rarely, aphids may infiltrate the tall leaves, but those aren’t difficult to control in muhly gardens. A misting of neem oil should get rid of them.

Diseases

Two diseases can occur, but the only serious one is tar spot. This fungal disease can damage or kill your plants. To keep this out of your garden, ensure your plants are spaced to allow for adequate airflow. If you haven’t divided your plant for a few years, that can improve airflow as well.

An additional disease that happens, albeit rarely, is rust. Common rust appears as speckling on the blade-like leaves. Too much moisture or poor airflow is a common cause. Thin out dense clumps as you would for tar spots.

III. Uses and Benefits 

Ornamental uses

Pink Muhly Grass only gets about 2-3 feet tall and wide at maturity, so it’s extremely versatile and can be planted just about anywhere. Here are a couple of landscaping ideas you may want to consider:

  • Pink Muhly is well suited to growing with companion plants such as The Magic Rose Camellia or Variegated Liriope. In fact, it’s one of the best ways to create a whimsical landscape. Try planting in groups of 3 to 5 in mixed beds for breathtaking color contrast.
  • Pink Muhly Grass looks stunning planted near a mailbox or as a focal point in your garden. You can effectively welcome others to your home by lining your driveway, or make visitors feel like they’re walking into a fairy tale by lining the walkways up to your front door.
  • You can also plant Pink Muhly Grass in containers. Use pots with holes for drainage and place them on a deck or patio as gorgeous outdoor living decor.

Other uses

Its hardiness and drought-tolerant properties make it a useful native ornamental grass in land reclamation, and it also has potential as fine fuel for burn management programs to reduce understory.

It is a known attractant for beneficial insects such as ladybug beetles, and is an excellent garden plant because of its low maintenance and general beauty. The clumping habit makes it excellent for use as wildlife cover, such as nests and shelter for native birds.

Muhly Grass (Muhlenbergia capillaris) Details

Common name Gulf Muhly, Hairgrass, Muhly Grass, Mule Grass, Pink Hair Grass, Pink Muhly, Pink Muhly Grass, Purple Muhly
Botanical name Muhlenbergia capillaris
Plant type Herbaceous Perennial
Hardiness zone 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
Growth rate Medium
Harvest time Fall
Height 2 ft. 0 in. - 3 ft. 0 in.
Width 2 ft. 0 in. - 3 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Clay
Flower color Cream/Tan
Leaf color Green