Prairie Onion (Allium stellatum) - pink flowers, illustrated plant card

Illustration

Prairie Onion

Allium stellatum

Also called autumn onion and cliff onion

Also comes in red and purple.

Prairie Onion blooms from July through September.

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Bloom calendar

Bloom time

Jul–Sep

checked

Hardiness

Zones 3–8

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Sun

Full sun

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Water

Low water

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Mature size

16 in × 12 in

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Type

Bulb

house classification

Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.

Plant it in full sun. It prefers low water. It is hardy in USDA zones 3–8. Expect it to reach about 16 in tall and 12 in wide at maturity, in roughly 1 year (a house reading).

Is Prairie Onion toxic to dogs or cats?

Listed as toxic to dogs and cats by University of Florida IFAS Extension.

Lists differ and none is complete. If a pet eats a plant and seems unwell, call a veterinarian or a pet poison helpline.

Verification

Planting record checked

What was checked

Nine facts were checked against named botanical sources, each recorded beside the sources that carried it: mature height and spread, hardiness zones, sun, water, bloom months and color, the trait tags, and years to mature size, which rests on a recorded house rule where no publisher states one and is marked so. Soil, diseases, pests, toxicity and the plant's own names have not yet been read for this plant, and its trait tags are the ones a feature uses rather than every word a page prints. Each fact above carries its own mark. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.

See the 6 sources it was checked against

When to plant Prairie Onion

Prairie Onion is a summer bulb planted in spring: get it in after the last frost, once the soil has warmed, May or June in zone 5, the middle of its hardy zones 3 to 8. It is hardy in zones 3 to 8, where it can stay in the ground over winter; colder than zone 3, lift and store it before the ground freezes. Expect flowers from July to September.

Month-by-month timing for your zone is on the planting calendar; if you garden near zone 5, the middle of this plant's hardy range, start with zone 5 in May. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.

How big does Prairie Onion get?

Illustration of Prairie Onion drawn to scale beside an adult — About 16 in tall and 12 in wide at maturity: knee-high beside an adult.

See Prairie Onion in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.

Where these facts come from

Prairie Onion's height, spread, hardiness zones, sun, water, bloom months and color and trait tags were checked against 6 published sources on October 25, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.

Missouri Botanical GardenPlant Finderheight, spread, hardiness zones, sun, water, bloom months and color and trait tags
Prairie Moon Nurseryheight, hardiness zones, sun, water, bloom months and color and trait tags
Chicago Botanic GardenPlant Finderhardiness zones, sun, water, bloom months and color and trait tags
greenroofplants.comEmory Knoll Farms, Green Roof Plantsheight, spread, hardiness zones, sun and bloom months and color
tnyards.utk.eduUniversity of Tennessee Institute of Agriculture, Tennessee Smart Yardsheight, sun, water, bloom months and color and trait tags
openprairie.sdstate.eduSouth Dakota State University, Open PRAIRIE Native Plant Collectionheight, sun, water and bloom months and color