Calochortus gunnisonii aka Gunnison's Mariposa Lily

Calochortus gunnisonii is a bulb-forming perennial in the lily family. Gardeners know it as Gunnison's mariposa lily or sego lily. It grows wild in the central and western United States. Its range includes the Rocky Mountains and the Black Hills. It lives in meadows, sagebrush country, and open woods. Wild plants also grow on sandy slopes and rocky hillsides. These sites range from moist ground to dry gullies.

The plant grows upright from an underground bulb. Thin green stems have smooth surfaces and may branch above. Its narrow green leaves look much like grass blades. Leaves at the base often fade before the flowers open. Leaves along the stem alternate and clasp the stalk. They can reach 1 foot (0.3 metres) in length. Their edges are smooth, and their surfaces lack hairs. The plant grows at a moderate rate.

Flowers open from May to July and attract bees. Each stem bears one to four cup-shaped blooms. Flowers measure about 1.5 to 2 inches across. Three broad petals sit among three slender sepals. Petals range from white to purple, with yellow hairs inside. A broken purple or maroon band marks the petal bases. A darker blotch also marks the narrow petal base. The fruit forms a capsule with three angled sides. These capsules hold flat seeds and appear in summer or fall.

Give this lily full sun and soil that drains well. It grows in loam, sand, and rocky ground. Cool, moist springs and dry summers suit its needs. Keep the bulbs dry from midsummer through late autumn. Sources place its hardiness within USDA zones 4–8. Wet winters make it hard to grow in Britain. Hot, humid parts of the southeastern United States also pose problems. Use it in rock gardens, meadow plantings, borders, or slopes. Small groups or mass plantings can show off the flowers.

Most plants have few pest problems, but excess moisture causes trouble. Bulb rot and powdery mildew can develop in wet conditions. Voles and gophers may eat the bulbs. Indigenous peoples and early settlers used the plant for food. Sources list bulbs, leaves, seeds, and flower buds as edible. Reports differ on whether raw bulbs are safe to eat. PFAF warns that raw bulbs may cause stomach upset. ASPCA lists this species as non-toxic to cats and dogs.