prairie wildflower
Swamp Onion
Allium validum
Also known as Pacific Onion, Tall Swamp Onion
Native to California, Idaho, Nevada, Oregon, and Washington and southern Canada
Mountains from Lake county, California to southern British Columbia, east to western Idaho and northeastern Nevada
- Light Full sun Sun tolerance
- Moisture Moist Moisture preference
- Zones 3–9 Cold to heat range
- Bloom Jun–Aug Flowering time
- Height up to 3 ft to 0.9 m
- Life cycle Perennial Annual to perennial
In the garden
A prairie wildflower for full sun and evenly moist soil. Its pink flowers peak in July. At up to 3 ft, it suits meadows and sunny borders. Hardy in USDA zones 3–9.
Growing conditions
Light
Full sun Partial shade Full shade
Moisture
Dry Moist Wet
Hardiness zones
Find your zone:
When it blooms
The Swamp Onion's pink flowers bloom June to August, peaking in July. This midsummer display draws bees and butterflies.
Swamp Onion blooms pinkFoliage
Pollinators & wildlife
- Bees Common Eastern Bumble Bee
also Red-belted Bumble Bee, Fuzzy-Horned Bumble Bee, Two-form Bumble Bee +4 more
Yellow-fronted Bumble Bee, Nevada Bumble Bee, Yellowish Cuckoo Bumble bee, Indiscriminate Cuckoo Bumble Bee - Butterflies California Tortoiseshell
also Clodius Parnassian, Sonoran Skipper, Nevada Cloudywing +2 more
Incisalia eryphon, Greenish Blue - Moths Wild Forget-me-not Moth
Butterflies that use this plant
Documented host and nectar records. Each links to a planting guide for that butterfly.
- Eastern pine elfinnectar
Full plant details
Where it grows
- Habitat
- PrairieThe wild plant community it grows in.
- Native range
- California, Idaho, Nevada, Oregon, and Washington and southern CanadaUnited States (5): CA, ID, NV, OR, WA. Canada (1): BC. Where it grows wild on its own, by state and province.
- Native distribution
- Mountains from Lake county, California to southern British Columbia, east to western Idaho and northeastern NevadaThe same native range, usually more exact than the state list, and often noting where it has spread beyond it.
Growing conditions
- Light
- Full sunHow much sun it takes, from full sun to full shade.
- Moisture
- MoistThe soil dampness it prefers, from dry to wet.
- Hardiness zones
- USDA 3–9 · Canadian 2–9The cold-to-heat climate range it survives.
- Soil
- Moist soilsThe soils it grows in naturally.
- Soil texture
- Light to medium (sandy to loamy)The soil grade it prefers, from sand to clay.
- Soil pH
- 6.2–8.0The acidity to alkalinity it tolerates (7 is neutral).
- Soil quality
- MediumHow rich a soil it needs. Many natives prefer lean soil and flop in rich beds.
- Water use
- HighHow thirsty it is, a rough guide to how often to water.
- Salinity tolerance
- NoneHow well it copes with salty soil, near roads or the coast.
- Lime (CaCO₃) tolerance
- MediumHow well it copes with chalky, lime-rich soil.
Growth & form
- Height
- up to 3 ft (to 0.9 m)Typical mature height.
- Life cycle
- PerennialWhether it lives a single season (annual), two (biennial), or returns for years (perennial).
- Growth rate
- ModerateA relative ranking versus other plants of the same type (USDA), not an absolute rate.
- Shape
- ErectIts overall silhouette.
- Root depth
- 8+ in (20+ cm)How far the roots reach, a guide to drought resilience and transplanting.
Flowers, foliage & fruit
- Type
- WildflowerWhat kind of plant it is.
- Bloom
- Jun–AugWhen it flowers.
- Flower color
- PinkThe bloom color, or colors.
- Fruit/Seeds
- ripens Jul–OctThe seed or fruit it sets after flowering.
- Toxicity
- None knownWhether any part is poisonous to people or pets.
Propagation & seed
- Cold stratification
- Not requiredWhether seed needs a cold, moist spell before it will germinate.
- Propagation
- Bulb, seedHow to start new plants.
- Seed spread rate
- SlowHow readily it self-sows. Slow or none means well-behaved, not a spreader.
- Seedling vigor
- LowHow strongly young seedlings establish.
- Vegetative spread
- SlowWhether it creeps outward or stays put in a clump.