In just three years, this self-sown clump has grown to 45 cm (18 in) wide and 25 cm (10 in) tall.
Sisyrinchium idahoense var. bellum is much shorter than its cousin S. striatum, putting it in the small-perennial or alpine category. In my garden, plants rarely grow to more than 15 cm – 20 cm (6 – 8 in) tall, although the self-sown clump shown above managed closer to 30 cm (12in) by leaning against an adjacent raised bed.
There is a great deal of variation amongst wild Blue eyed grass with some growing up to 30 cm such as S. idahoense (illustrated here). These medium-height Sisyrinchiums are rather rare in cultivation, whereas the smaller (10-15 cm) varieties are relatively common in nurseries, often found in the alpine section.
These short cultivars are often derived from S. bellum or S. angustifolium, although the original parentage is often difficult to find. These ‘alpine’ cultivars include blue and purple flowered E.K Balls, Marion, Devon Skies, Moody Blues, Lucerne and Rocky Point; Pinkish-brown Biscuitella and bright yellow S. californica. All of them have foliage approximately 5-10 cm (2-4 in) long and flower at 10-15 cm (4-6 in) high.
Despite its small stature, the flowers of these miniature sysirinchiums are almost the same size as those of their bigger cousin S. striatum, being approximately 1.5-2 cm (½-¾ in) across. Individual flowers only last for a day or two, but appear in succession for several weeks in summer. The flowers are nyctanistic, meaning they close up at night and open again the next morning.
The foliage of blue-eyed grass is a good bright green. Individual tufts are arranged in the iris-like fan of flat blades with asymmetric knife-shaped tips. Partly evergreen, a clump can look quite neat in the spring as new foliage emerges (see bottom photo, below). After flowering, however, the clumps tend to lose this tidy appearance and by winter can best be described as untidy.
Each clump expands by two methods: first by stolons (underground stems) producing new foliage fans close to the main clump. The second is via offsets, whereby miniature plants grow on the end of thin, arching stem (see top photo, below).
These little offset plants are sometimes held aloft for a few days, floating above the main plant, until gravity brings them down to earth, at which point they eventually take root (see photo below). These offset stems can be over 10 cm (4 in) long, allowing blue-eyed grass to slowly weave itself between other low-growing plants. You can see the effect of this in the featured background image at the top of this post.
Narrow leaved blue-eyed grass has many quirky and charming botanical details that will appeal to those who are happy to get up close and personal. In many cases, this will mean getting down on hands and knees to properly observe them. Growing it in pots can make close observation easier; or you can rely on macrophotography, like the shots below.
REQUIREMENTS — To succeed S. angustifolium needs a sunny open site where it is not too crowded, although it will manage in part shade too. Keep it moist until it is established, after which it will be fairly drought tolerant. That said, it seems to need more consistent moisture than S. striatum, especially in the spring.