Allium unifolium


American onion
A compact perennial to 30cm in height, with short grey-green basal leaves and umbels of relatively large, star-shaped rose-pink flowers in late spring
Synonyms
Allium grandisceptrumAllium murrayanum misapplied
Buy this plant
Size
Ultimate height
0.1–0.5 metresTime to ultimate height
2–5 yearsUltimate spread
0–0.1 metreGrowing conditions
Moisture
Moist but well–drained, Well–drainedpH
Acid, Alkaline, NeutralColour & scent
Stem | Flower | Foliage | Fruit | |
Spring | Pink | Green Grey Silver | ||
---|---|---|---|---|
Summer | Green Grey Silver | |||
Autumn | ||||
Winter |
Position
- Full sun
Aspect
South–facing or West–facing or East–facing or North–facing
Exposure
Sheltered Hardiness
H5Botanical details
- Family
- Amaryllidaceae
- Native to the UK
- No
- Foliage
- Deciduous
- Habit
- Columnar upright
- Genus
Allium are bulbous herbaceous perennials with a strong onion or garlic scent, linear, strap-shaped or cylindrical basal leaves and star-shaped or bell-shaped flowers in an umbel on a leafless stem
- Name status
Correct
- Plant range
- USA Oregon to W California
How to grow
Cultivation
Easy to grow in fertile well-drained soil. Add grit when grown in clay soils to improve drainage. See allium cultivation for further advice
Propagation
Propagate by seed, sowing seeds in containers with bottom heat when ripe and grow on under glass. Remove offsets in spring and grow on under glass for 2 seasons
Suggested planting locations and garden types
- Gravel garden
- Rock garden
- Flower borders and beds
Pruning
No pruning required
Pests
Generally pest free
Diseases
Generally trouble-free: Onion white rot and a downy mildew may occur
Get involved
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.