By Valerie Boss
GNPS is pleased to introduce blue-eyed grass (Sisyrinchium angustifolium) as our 2025 Plant of the Year. Blue-eyed grass is a low- growing monocot, with straight, flat, narrow leaves. It can look a lot like a clumping grass, especially when the foliage becomes thick and crowded (figure 1), but grass is a misnomer. Blue-eyed grass is a member of the iris family, Iridaceae. The resemblance to irises becomes more apparent when few leaves are present (figure 2), revealing foliage that is fan-shaped, having equitant leaves.
Figure 1 (left) – Blue-eyed grass has a similar appearance to a clumping grass, but is not a grass (Photo by V. Boss). Figure 2 (right) – Blue-eyed grass is part of the iris family, as apparent in this presentation of this foliage (Photo by M. Strickland).
Blue-eyed grass blooms from March through May. Leafless, branched stalks poke up from the base, each bearing multiple 6-parted flowers. Only one flower per stalk blooms at a given time, but clumps can have many stalks and are often decked with flowers (figure 3). Flower buds emerge from within a single spathe (papery covering), which is typical for members of the Iridaceae family. Each flower is less than 1” across, with identical sepals and petals, called tepals. These are oval, with pointed tips that jut out from the terminal end. The flower color is bright blue or sometimes violet. The hue darkens close to the center, which is vivid yellow (figure 4). In late spring, the flowers of blue-eyed grass develop into seed heads shaped like round balls. Figure 5 shows a plant in May with both a flower and single green seed head. By late summer, the seed heads turn deep brown and split open, spilling out tiny dark seeds.
Figure 3 – Only one flower per stalk blooms at a given time, but clumps can have many stalks (Photo by E. Honeycutt).
Unlike grasses, which have fibrous roots, plants in the Iridaceae family have either underground storage organs (corms or bulbs) or rhizomes. Blue-eyed grass is no exception; the genus Sisyrinchium is rhizomatous. However, there is one aspect in which blue-eyed grass diverges from the general Iridaceae phenotype. Microscopically, a hallmark of the Iridaceae is the presence of calcium oxalate crystals, particularly styloids, within the tissues. Sisyrinchium is one of only 3-4 genera in a family of over 300 genera that lack calcium oxalate crystals entirely.
The genus name Sisyrinchium appears to be derived from the species name for a different member of the Iridaceae family, Barbary nut iris (Morea sisyrinchium). This plant has a corm tunic resembling shaggy goat hair (Greek word “sisyra”), so the appellation makes sense. Why Sisyrinchium was chosen as the genus name for a group of plants without a corm is a mystery. The species name angustifolium means “narrow-leafed”, which is a fitting description for a plant with grass-like foliage.
Figure 4 (left) – The hue of the flower darkens close to the center (Photo by E. Honeycutt). Blue-eyed grass in May with both a flower and single green seed head (Photo by M. Strickland).
Both foliage and flowers of blue-eyed grass lend character to a planted area; it is a lovely garden plant. In the wild, the species favors open forest, water edges, and meadows. Tolerant of full or partial sun, it can handle some dryness, but won’t thrive in arid environments. Plant blue-eyed grass in conditions that mimic the natural habitat and it will do fine. It can be found in native plant nurseries and online. Take care not to mistake the non-native, white-flowered, S. iridifolium, aka S. microcanthum, for a variant of the native S. angustifolium. Blue-eyed grass can be propagated by seed, as well as by division. Plants should be divided every few years to maintain vigor; otherwise, clumps may die out. The species makes a great ground cover—consider it as an alternative to liriope–and its flowers attract many bees and butterflies.
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Plant of the Year shirts are available in our online store. The 2025 design should be ready to order in March, so stay tuned!
