The Iris Family (Iridaceae) in the Park

Mountain iris (Iris missouriensis) are among the most striking and beautiful of Rocky Mountain National Park's late spring wildflowers. They bloom from late May till late June, and are often found in meadows with golden banner (Thermopsis divaricarpa). Mountain iris are sky blue to lilac in color and golden banner are a bright chrome yellow, so the combination is breath-taking.

There are three members of the Iris family (Iridaceae) reported from Rocky Mountain National Park. All have long narrow leaves with parallel veins, three petals, and three sepals. Mountain iris have the form most people associate with the name iris, with their petals standing upright (called standards in cultivated iris), and sepals hanging downward (called falls in cultivated iris). The dark purple and yellow veins on the sepals or falls are honey guides directing insects to the nectar and to doing their jobs as pollinators. The mountain iris is by far the most showy member of the iris family in the park.

Blue-eyed grass (Sisyrinchium montanum) and pallid blue-eyed grass (Sisyrinchium pallidum) are much smaller, yet charming early summer-blooming (late June to early July) wildflowers. In both species, flowers are generally smaller in diameter than a dime. What blue-eyed grass lacks in size, it more than makes up for in appeal. It is generally close to a true medium blue in color, though a few flowers in most populations may have a more purple cast. All have bright yellow centers. Blue-eyed grass flowers only open in bright sunlight, so afternoons are a better time than mornings to enjoy them.

Pallid blue-eyed grass is a very rare species. It is listed by the Colorado Natural Heritage Program as "G2 Imperiled globally, and G3 Vulnerable through its range or found locally in a restricted range." It is also listed by Colorado Natural Heritage Program as "State Imperiled because of rarity (six to 20 occurrences, or 1,000 to 3,000 individuals), or because other factors demonstrably make it very vulnerable to extinction throughout its range." While these rankings should not be interpreted as legal designations, they certainly indicate that pallid blue-eyed grass is extremely rare. Fortunately, populations in Rocky Mountain National Park appear to be healthy. Pallid blue-eyed grass flowers are a very pale blue, appearing almost white. If you are in the park in late June or July, you may get a chance to see and photograph this lovely and very rare flower.

Last updated: March 31, 2012

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