Ornamental Onions

You'll know they're in the onion family from the mild pungent odor when leaves are cut, but they won't bring tears! Many species/cultivars add color from spring through fall. All have spherical flower heads atop single stems rising from clumps of narrow, onion-like leaves.

About This Plant

All in genus Allium. Late spring/early summer bloomers form bulbs planted in fall (like daffodils). Later bloomers develop rhizomes, sold as container perennials (chives fall here). Early bloomer foliage fades quickly; later bloomers' foliage stays attractive longer. Most hardy Zones 4–8.

Notable Varieties

• A. aflatunense 'Purple Sensation': 4–5 inch violet-purple globes on 2–3 ft stems, mid-late spring.
• 'Globemaster': Volleyball-sized silvery purple heads on 3 ft stems, weeks of bloom, foliage holds well.
• A. schubertii (Tumbleweed Onion): 12 inch rose-pink spidery heads, late spring, Zones 7–9.
• A. sphaerocephalon (Drumstick Allium): 1–2 inch oval reddish-purple heads, midsummer.
• A. senescens subsp. glaucum (Corkscrew Onion): Rhizomatous, 2 inch lavender-pink heads mid-late summer, distinctive corkscrew foliage.
• A. triquetrum: Part shade, 2 inch nodding white flowers, late spring.
• A. thunbergii 'Ozawa' (Japanese Onion): 1 inch rosy-pink globes on 1 ft stems from September, rhizomatous, container-sold.

Site Selection

Well-drained soil, full sun (exceptions noted). Place early bloomers where surrounding plants hide fading foliage.

Planting Instructions

Bulbous types: mid-fall, cover bulbs with 2x diameter soil (3–5 in small, 6–8 in large). Space 3–4 in (small) to 12 in (large). Container alliums anytime. Loosen soil 12–15 inches, add 2–4 inches compost.

Care

Deadhead to prevent self-sowing. Feed bulbous types in fall with organic fertilizer (roots active even without foliage). Poor soil: second light feed in spring as foliage emerges. Feed rhizomatous types early spring. Spring: thin compost + 2-inch mulch. Water if rainfall <1 inch/week. If flowering declines, divide bulbous types as flowering finishes/foliage ripens. Divide rhizomatous types early spring.