Dichelostemma congestum aka Fork Tooth Ookow

Dichelostemma congestum is a perennial wildflower in the asparagus family. Gardeners also call it ookow or fork-toothed ookow. It grows in western North America, from British Columbia south to California. Kew gives a narrower range, from Washington to north-central California. Its wild sites include grassy hillsides, mountain slopes, and open meadows. The plant grows upright and forms clumps. Over time, seed and underground bulbs can help it form colonies.

Garden plants reach about 1.6–3.3 feet (0.5–1 metre) tall. The RHS describes flowering plants around 3 feet (0.9 metre) tall. Published widths differ a great deal between sources. The RHS gives a spread of 0.3 feet (0.1 metre). NC State lists 3–4 feet (0.9–1.2 metres). Narrow green leaves grow near the base and look like grass. They die back as the flowers begin to open. The tall, thin stems have smooth surfaces and no scent. Flowering stems can curve or twist rather than stand straight.

Small flowers crowd together at the ends of long stems. Each dense raceme can hold six to fifteen flowers. The tubular blooms reach about 0.8 inches (0.02 metre) long. Their colours include blue, lilac, purple, and pink. NC State also records pale purple to green blooms. Flowering dates vary with place and growing conditions. Chicago Botanic Garden lists March through June. NC State gives April through June; the RHS gives early summer. Bees visit the flowers, which also work as cut stems.

Give this plant full sun and soil that drains well. It can also cope with some shade and poor soil. Sources list sand, loam, chalk, and clay as suitable soil types. Their pH guidance spans acid, neutral, and alkaline soils. The plant tolerates drought, though Chicago lists moderate water needs. Soil should dry out after the flowers fade. The RHS advises autumn planting, about 0.3 feet (0.1 metre) deep. It also calls for warmth and dryness after bloom. Chicago lists USDA zones 7–9; NC State extends this to 10a. The RHS rates it H3 for mild parts of Britain.

Use ookow in borders, containers, patio plantings, or drought-tolerant gardens. NC State describes it as easy to grow with little upkeep. The RHS says it needs no pruning. Both sources report few or no pest and disease problems. Grow new plants from seed or separate offsets in late summer. Seedlings may take several months to appear. NC State lists it as non-toxic to cats, dogs, and horses.