How to Grow and Care for Blue-Eyed Grass

Blue eyed grass plant with small purple flowers on end of stems

The Spruce / Adrienne Legault

Despite the name, blue-eyed grass (Sisyrinchium angustifolium) is not a true grass, but is rather a native North American perennial with a clump-forming growth habit and narrow blade-shaped leaves. A member of the iris family, blue-eyed grass produces clusters of blue-violet 1/2-inch flowers with yellow eyes in spring.

This is a native wildflower that is often found in large colonies in moist meadow areas, and it will behave similarly in the garden, though you'll need to plant several specimens so they can cross-pollinate and produce seeds. Blue-eyed grass is usually planted from potted nursery starts in the spring, or it can be sown by seeds directly sown in the garden during the fall or started indoors in late winter. It is a relatively fast-growing plant, though it may take two seasons to flower if you plant it from seeds.

Common Name Blue-eyed grass, narrow-leaved blue-eyed grass
Botanical Name  Sisyrinchium angustifolium
Family Iridaceae
Plant Type Perennial wildflower
Mature Size 18–24 in. tall, 6–12 in. wide
Sun Exposure Full, partial
Soil Type Moist, well-drained
Soil pH Acidic to neutral (5.0 to 7.0)
Bloom Time Late spring
Flower Color Blue-violet
Hardiness Zones 4–9 (USDA)
Native Area Eastern North America (Northern Florida to Canada)

Blue-Eyed Grass Care

Blue-eyed grass is quite easy to grow in relatively poor soil, provided it is moist and well-drained, Small groups of plants will readily spread and self-seed to form ground-cover colonies. Cut blue-eyed grass back after it is done flowering if you want to keep it from self-seeding and thereby restrict its spread.

Divide blue-eyed grass every two or three years to revitalize it and propagate new plants. This plant is generally not bothered by insects or diseases, and even deer tend to leave it alone.

Blue eyed grass plant with small purple flowers and buds closeup

The Spruce / Adrienne Legault

Blue eyed grass plant with small purple flowers and thin leaf blades closeup

The Spruce / Adrienne Legault

Blue eyed grass plant with small purple flowers with yellow centers and buds closeup

The Spruce / Adrienne Legault

Light

Although it is tolerant of light shade, blue-eyed grass will flower better and show denser foliage growth when grown in full sun.

Soil

Blue-eyed grass does best in poor to average soil, but it must be moist and well-draining. It prefers an acidic or neutral soil pH of 5.0 to 7.0. Soil that is very rich is not ideal for these plants.

Water

Blue-eyed grass performs best in moist soils. In native locations, it is often found in damp meadows and along streams, and it will soon decline if conditions are allowed to dry out for too long. It is best to water in the early morning hours, and during dry hot periods, you may need to water daily, especially if the plants are growing in less-than-ideal conditions. This plant normally will do well with the standard "1 inch per week" (rainfall and/or irrigation), but this can vary considerably depending on soil composition, temperatures, and other factors.

Applying mulch is normally a good way to preserve soil moisture, but in the case of blue-eyed grass, mulch covering the root crowns can encourage rot, so make sure to keep mulch and compost well away from the plant leaves and stems.

Fertilizer

An occasional application of compost will be sufficient and even that is often unnecessary. Chemical fertilizers may cause the plants to withhold flowers, as they force the plants to put energy into green growth at the expense of flowering.

Types of Blue-Eyed Grass

In addition to the species plant, there is one notable cultivar of Sisyrinchium angustifolium, 'Lucerne'. This cultivar has notably larger flowers, up to 1 inch across, and it blooms considerably longer, sometimes well into late summer.

In addition, there are other native species of the Sysyrinchium genus that are popular landscape plants:

  • S. striatum (pale yellow-eyed grass) is a South American native with yellow flowers that blossom in late spring and early summer. It is hardy in zones 7 to 8.
  • S. bellum is another form of blue-eyed grass, native to California and Oregon, and hardy in zones 7 to 8. It is very similar to S. angustifolium, but is a better choice for dryer western gardens.
  • S. mucronatum (needle-tip blue-eyed grass) is another North American native, but it has a broader hardiness range, zones 3 to 8. It is a slightly smaller plant than S. angustifolium, with delicate star-shaped flowers.
  • S. campestre (prairie blue-eyed grass) is very similar to S. angustifolium, but it is a smaller (6-inch) plant that is hardy as far north as zone 2 and blooms almost a month earlier in the spring.

Pruning

Colonies of blue-eyed grass can be shorn back after blooming is complete to prevent unwanted self-seeding. Some gardeners like to deadhead the spent flowers to promote new buds and a longer bloom period, but it is not essential.

Propagating Blue-Eyed Grass

New plants are easy to propagate by digging up and dividing root clumps in the spring. Here's how:

  1. Use a shovel or trowel to dig up an entire intact clump of blue-eyed grass in the spring, as new growth is just beginning. Shake loose most of the soil, or spray with a hose to remove the soil.
  2. Gently tug apart the root clump into sections. Each section should have at least three or four growth shoots.
  3. Replant the sections in the desired locations, and water well until new growth is well established.

Blue-eyed grass responds best to being divided in this way every two or three years to rejuvenate the clump, but if your goal is simply propagation, you can also simply dig up small offset plants around the mother plant and transplant them into new locations. Self-seeded volunteer plants can also be transplanted in this way.

How to Grow Blue-Eyed Grass From Seed

If you collect seeds from plants, remember that they need cold stratification in order to germinate. Simply scatter the seeds over the area where you want them to grow in the fall and let the winter cold provide the necessary stratification. If you prefer to start them indoors in late winter, then store the seeds in the refrigerator for six weeks before planting them in small pots, just barely covered with potting mix (they need light in order to germinate). Keep the planted seeds in a bright location between 50 and 60 degrees until they germinate and sprout. Plants started from seeds may not flower until their second season, so be patient.

Overwintering

These hardy wildflowers need no particular winter protection, but you may want to cut down the plants to remove seed heads, which can cause undesirable self-seeding. But leave the seed heads in place if you want to attract birds.

How to Get Blue-Eyed Grass to Bloom

Blue-eyed grass is normally quite generous with its flowers, provided it is getting plenty of sun and moisture. But keep these elements in mind for maximum flower production:

  • Blue-eyed grass prefers a relatively lean soil, and it may paradoxically resist blooming if growing in soil that is too rich. If your plants fail to bloom, try withholding fertilizer to see if this helps. Even excessive mulch can make the soil too rich, so neglect is often the best strategy for robust blooming.
  • Blooming may slow down if plants become overly root-bound, so lifting and dividing the plants every two or three years may help keep them flowering.
  • Deadheading spent flowers may also prompt the plant into a longer bloom period, since it nudges the plant into producing additional flower buds.

Common Problems With Blue-Eyed Grass

When growing in favorable conditions, there are very few complaints with blue-eyed grass. Plants that collapse at the soil line may be experiencing root rot, which most often happens if the soil is covered with a dense layer of mulch or plant debris. If you mulch at all, make sure to keep an open area about 3 inches around the base of the plants, which will prevent moisture from rotting the crowns.

FAQ
  • How can I use this plant in the landscape?

    Blue-eyed grass is not an extremely showy plant, so it is favored mainly by native plant enthusiasts. The flowers are only about 1/2 inch across, and they tend to pucker up later in the day as conditions warm. But it is a plant that naturalizes well and can make a good ground cover plant for moist, sunny areas, such as rain gardens, low-lying meadows, sunny woodland gardens, and other natural areas. It is also sometimes used in rock gardens.



  • How long does blue-eyed flower live?

    Individual plants are relatively short-lived (a few years), but once colonized, the spreading roots and self-seeding habit will keep a patch of blue-eyed flower growing almost indefinitely. Don't be surprised if the clump "travels" and moves around the garden as it spreads out from the original location while the original plants die out.

    You can also perpetuate the colony by lifting and dividing the roots every couple of years.

  • Does this plant attract wildlife?

    Like most wildflowers, blue-eyed grass has flowers that are appealing to a wide range of bees, butterflies, and other pollinators. Seed-eating birds will also enjoy the tiny black seeds that are found in the brown or black seed pods left behind after the flowers have faded. If you want to encourage birds, avoid deadheading and leave the flower stalks in place into the winter.