Tall central Asian ornamental allium with stems reaching 1.5 m and dense 15 cm spheres of small lilac-purple star flowers above broad strap-like leaves. A dramatic vertical accent for the late-spring border.
Hardiness ratings
| System | Rating | Temperature range | How to read it |
|---|---|---|---|
| USDA hardiness zone | Zone 5–9 | −28.9 °C to −1.1 °C | Plant tolerates down to this zone |
| RHS hardiness rating | H6 | −20 °C to −15 °C | Plant needs at least this level of cold tolerance |
| Canadian plant hardiness zone | Zone 5–8 | −23 °C to −1 °C | Plant tolerates down to this zone |
| Australian (ANBG) zone | Zone 1–5 | −15 °C to 10 °C | Plant tolerates down to this zone |
Growing notes
- Plant in mid-to-back sunny borders — flower stems reach 1.5 m, the spheres held high above accompanying perennials
- Strap leaves are large and yellow as the flower opens — site with later-emerging perennials in front to mask the foliage
- Outstanding bee forage — flowers May–June
- Dried flower heads persist as long-lasting garden structure
Pet caution: Giant onion is listed as potentially harmful to cats and/or dogs. Keep pets from grazing on it, and contact a vet if you suspect your animal has eaten some.
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Related plants
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