Blue-eyed grass

Sisyrinchium bellum

small ground bush with long stringy green leaves and purple flowers
Blue eyed grass in the roof garden in the Nature Center | Nature Center | April 2009

Blue-eyed grass (Sisyrinchium bellum) is not a grass but an iris, native to California, western Oregon and northwestern Mexico. It is the only native iris in the Reserve. Unlike the showy garden iris, blue-eyed grass has a delicate flower with sepals and petals that look alike and that form a shallow, sometimes inverted saucer around the stamens and pistil. At the base of each blue petal is a bright yellow, fringed shape; together these form a yellow spot at the center of the flower. Blue-eyed grass might be better named “yellow-eyed non-grass.”

Blue-eyed grass is a popular plant in native plant gardens. In spring, it blooms cheerfully in the roof garden at the Nature Center as well as along the trails in East Basin.

Other Common Names:

western blue-eyed grass

Description 4,11,26,35,59

Blue-eyed grass is a short-lived perennial herb that arises from a shallow, horizontal stem (rhizome). Each rhizome produces one to several ascending or vertical shoots, up to 2 feet (60 cm) long. Each shoot consists of a few basal leaves and a terminal inflorescence. The green or blue-green, strap-like leaves are tightly folded at the midrib. Leaves are folded around each other at their bases, from which point all leaves fan out in a flat spray. The plant goes dormant in late summer.

Up to a dozen flowers occur in a loose compound cluster at the end of a strongly flattened, green peduncle. At a node where a lateral branch arises, the main axis is often angeled and a leafy bract may be present. Flowers open sequentially so that one or a few are open at any time. Flowers are radially symmetrical with diameters up to 1 1/4 inches (3.2 cm). The three petals and three sepals are similar (together called tepals). The tepals are obovate to lanceolate and dark blue/purple (occasionally pale or white) with a bright yellow fringed shape at the base and with radiating darker lines. At the outer end of each tepal is often a small point, arising from a shallow, rounded indentation. Tepals form a shallow or inverted saucer around the stamens and pistil. There are three stamens, their filaments fused into a column around the pistil; the anthers form a bright yellow scalloped umbrella on top. There is one pistil with an inferior, three-chambered ovary. The style is largely concealed by the filament column but can sometimes be seen as a tiny spire projecting from the top of the anther ring.3 Flowers bloom from Feb. to May.1

The fruit is a globular dry capsule that splits open at maturity to release numerous small, rounded seeds.

Field of grass with small purple flowers

Santa Carina trailhead | April 2015

6 petal purple flower with a yellow center

Stamens fused into a column around the pistil | Santa Carina trailhead | April 2011

5 small brown seed pockets on end of a stick

Globular, dry seed capsules | Santa Carina trailhead | April 2015

Distribution 2,7,89

Blue-eyed grass is native to California, western Oregon, and north-western Mexico, primarily below 4000 ft. It is associated with a number of vegetation types from yellow pine forest and oak woodland to grasslands, chaparral, coastal sage scrub and riparian and wetland areas. In spite of its occurrence on the sandy soils of the Reserve, blue-eyed grass is reported to prefer heavy clay soils.8,59

Blue-eyed grass occurs sporadically throughout the Reserve, especially east of the freeway. The best concentration is in a field northwest of the Santa Carina trailhead. It is a spectacular sight on a sunny day, visible but not accessible from the trail. Plants are also abundant near the Santa Inez trailhead and they have been planted around the Nature Center.

Classification 23,44,59,143

Blue-eyed grass is a monocot angiosperm in the iris family (Iridaceae). As distinguished from dicots (the other traditional group of angiosperms, or flowering plants), monocots have flower parts in multiples of three (instead of five or four) and there is only one cotyledon or “seed-leaf” in the embryo (instead of two); there are also differences in pollen morphology and in the arrangement of the vascular tissue.176 Although not always accepted by modern taxonomists, the simplicity of these groups makes them useful for general purposes.

Members of the iris family are perennial plants, arising from a bulb, corm or rhizome. The plants grow erect, and have leaves that are grass-like, with a tight central fold. The iris family contains many well known ornamental garden plants such as gladiola, crocus, freesia and, of course, iris, “one of the most recognizable plants in the world.”44

Blue-eyed grass is the only native iris in the Reserve; four other members of this family are escaped garden plants.48 Plants in the blue-eyed grass genus, Sisyrinchium, differ from the typical garden iris in that the sepals and petals are similar;81 in iris the sepals look like petals but flare outward and downward (the “falls”) while the petals stand upright (the “standards”).

Alternate Scientific Names:

Sisyrinchiume astwoodiae, Sisyrinchium greenei, Sisyrinchium hesperium, Sisyrinchium maritimum

Jepson eFlora Page
close up of purple flower with 6 petals

Santa Carina trailhead | March 2015

close up of green string leaves coming out of dirt

The bases of the leaves fold tightly around each other | April 2015

field filled with purple flowers

Santa Carina trailhead | April 2011

Ecology 257,258

Flowers of blue-eyed grass close at night,35 and sometimes during a cloudy day. This is a response seen in diverse flowers including tulips, crocuses, and dandelions, but most flowers remain open day and night until they are pollinated. It makes sense for a flower to be open when its pollinators are active, but why close when they are not? Darwin thought that flowers might close at night to protect the reproductive organs from frost. Over the years, other reasons have been proposed: to keep the pollen dry and powdery so that is it more easily dispersed, to retain the flower’s scent, to protect the flower parts from night-time grazers, to reduce the chance of contact with pathogens. Any, or all of these reasons may be, or may have been, important for some plants, somewhere, sometime. We may never know the exact combination of adaptations that produced this response in blue-eyed grass. Whatever the reasons, a spectacular field of blue-eyed grass may vanish completely on a cloudy morning.

Light green grass

Photo taken at 6am | April 2016

Field of green grass with purple flowers

Photo taken at 1pm | April 2016

field filled with purple flowers

Stonebridge Mesa | April 2012

Human Uses  

The Spanish in early California called blue-eyed grass “azulea.”23 They boiled the roots into a tea to relieve fevers and believed that a person could subsist for days on azulea tea alone.

In modern California, blue-eyed grass is a popular plant in native plant gardens.24,59 It is one of the plants in the roof garden of the Nature Center.

bush of purple flowers

Santa Carina trailhead | April 2010

2 purple flowers

Santa Carina trailhead | March 2015

Long green grass with purple flowers

In the roof garden at the Nature Center | April 2008

Interesting Facts 41,259

The opening of a flower during the day and closing at night (or vice versa) is called “nyctinasty”. Blue-eyed grass is nyctantistic. Among nyctanistic flowers, there is a wide variety of opening and closing times, and the timing may be very precise. In the mid-18th Century, Linnaeus proposed a “flower clock”, a flower bed designed as the face of a clock, planted so that the flowers in each hourly segment opened at the correct time according to the true clock. It is uncertain whether this was ever created successfully.

close up of purple flower on stick

Santa Inez trailhead | April 2016

close up side profile of purple flower leaves and pollen

Santa Carina trailhead | April 2015

Bundle of purple flowers

Photo credit: Barbara Wallach | March 2003

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