Allium platycaule

Common Names

Broadstemmed Onion, Flat-Stemmed Onion

Summary

Broad-stemmed onion is a bulb-forming perennial herb native to the western United States, including California, Oregon, and Nevada, typically found on slopes at elevations of 1500–2500 m. It grows to 6–12 inches tall with a gray bulb 2–3 cm wide, a thin, strongly flattened scape up to 25 cm long, and long flat, sickle-shaped leaves; the umbel atop the stem may contain up to about 90 flowers, each pink to magenta with yellow anthers, creating a dense ball of filaments and a striking display in late spring.

In cultivation it prefers full sun to partial shade and well-drained soils, is drought-tolerant, and hardy in USDA zones 5–9; it occurs on dry flats, screes and slopes and suits rock gardens, alpine gardens, and naturalized plantings; it forms bulbs in clusters along a rhizome and attracts bees and butterflies; leaves, bulbs, and seeds are edible and were used by the Paiute.

Lifecycle

Perennial

Height

4-12 inches

Spread

10-24 inches

Hardiness Zones

Zones 5-9

Sunlight Requirements

Ideally full sun. Tolerates partial shade

Soil Type

Well-drained soil, ranging from sandy to loamy.

Soil Drainage

Well-drained

Soil pH

Mildly acidic, neutral, or mildly alkaline soils.

Bloom Color

Bright pink to magenta

Bloom Time

Spring

Foliage Color

Blue-green

Seasons of Interest

Spring and Summer

Propagation Methods

Seed, Division

Attracts Wildlife

Attracts bees, Attracts butterflies