Home/Species/ Swamp Onion

Allium madidum

S. Wats.

Swamp Onion

G3Vulnerable (G3G4) Found in 1 roadless area NatureServe Explorer →

G3VulnerableGlobal Rank

Medium - lowThreat Impact

Identity

Unique IDELEMENT_GLOBAL.2.142787

Element CodePMLIL021E0

Record TypeSPECIES

ClassificationSpecies

Classification StatusStandard

Name CategoryVascular Plant

Endemicendemic to a single nation

KingdomPlantae

PhylumAnthophyta

ClassMonocotyledoneae

OrderAsparagales

FamilyAmaryllidaceae

GenusAllium

Concept Reference

Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

Conservation Status

Rank Method Rank calculation - Biotics v2

Review Date2023-02-09

Change Date2023-02-09

Edition Date2023-02-09

Edition AuthorsStoner, N., rev. L. Morse (1994), rev. J. Beckman (1996), rev. C. Nordman (2023).

Threat ImpactMedium - low

Range Extent20,000-200,000 square km (about 8000-80,000 square miles)

Number of Occurrences21 - 300

Rank Reasons

Swamp Onion is endemic to the northwestern United States, occurring only in the Blue Mountains in Oregon and Idaho. There are at least 50 and perhaps more than 80 occurrences, and a total at least several thousand plants. Threat impacts are probably medium to low, including from recreation, timber harvest, and extreme or long-term drought, such as may be more common with climate change.

Range Extent Comments

The Swamp Onion (Allium madidum) occurs in the northwestern United States. It is endemic to the Blue Mountains of eastern Oregon, and to a lesser extent nearby western Idaho, occurring near Payette Lake in Valley County, and near New Meadows in Adams County, Idaho. The range extent is estimated to be about 34,000 square kilometers (Flora of North America Editorial Committee 2002, Meyers et al. 2015, NatureServe 2023, SEINet 2023, Spahr et al. 1991).

Occurrences Comments

The number of occurrences is uncertain, but could be 60 - 80, or more (NatureServe 2023, SEINet 2023).

Threat Impact Comments

The overall threat impact to Swamp Onion is likely medium to low, threats include recreation and timber harvest impacts (Spahr et al. 1991). The mountain wet meadows and seep habitat where it occurs could be impacted by reduced rainfall, reduced mountain snowpack, and extreme drought such as may become more frequent with climate change.

Ecology & Habitat

Habitat

Swamp Onion occurs in the Blue Mountains in open mixed conifer woodlands, gravelly seeps, seasonally wet meadows (along low ground water courses and vernal pools), and scablands. Soils include gravelly, rocky, clay, or sandy soil with humus, it occurs at 1000-2200 m (3300-7200 feet) elevation (Flora of North America Editorial Committee 2002, Meyers et al. 2015, SEINet 2023, Spahr et al. 1991). It also has been found in disturbed areas and in a meadow heavily grazed by cattle and sheep (Steele et al. 1981).

Reproduction

Swamp Onion flowers from early May through early July. In addition to reproduction through seed production, small bulblets form underground with the bulbs, and can develop into new plants (Spahr et al. 1991).

Terrestrial Habitats

Woodland - ConiferGrassland/herbaceous

Palustrine Habitats

TEMPORARY POOLHERBACEOUS WETLANDBog/fenRiparian

Other Nations (1)

United StatesN3

Province	Rank	Native
Oregon	S3	Yes
Idaho	S3	Yes

Threat Assessments

Threat	Scope	Severity	Timing
5 - Biological resource use	Restricted (11-30%)	Moderate or 11-30% pop. decline	High (continuing)
5.3 - Logging & wood harvesting	Restricted (11-30%)	Moderate or 11-30% pop. decline	High (continuing)
6 - Human intrusions & disturbance	Restricted (11-30%)	Moderate or 11-30% pop. decline	High (continuing)
6.1 - Recreational activities	Restricted (11-30%)	Moderate or 11-30% pop. decline	High (continuing)
11 - Climate change & severe weather	Pervasive (71-100%)	Moderate - slight	High (continuing)
11.2 - Droughts	Pervasive (71-100%)	Moderate - slight	High (continuing)

Plant Characteristics

DurationPERENNIAL

Economic Value (Genus)Yes

Roadless Areas (1)

Oregon (1)

Area	Forest	Acres
Potamus	Umatilla National Forest	5,389

References (7)

<div>Meyers, S.C., T. Jaster, K. E. Mitchell, and L.K. Hardison, editors. 2015. Flora of Oregon. Volume 1: Pteridophytes, Gymnosperms, and Monocots. Botanical Research Institute of Texas, Fort Worth, TX. 608 pp.</div>
Flora of North America Editorial Committee (FNA). 2002a. Flora of North America north of Mexico. Vol. 26. Magnoliophyta: Liliidae: Liliales and Orchidales. Oxford Univ. Press, New York. xxvi + 723 pp.
Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
NatureServe. 2023. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
Southwest Environmental Information Network (SEINet). 2023. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2023).
Spahr, R., L. Armstrong, D. Atwood, and M. Rath. 1991. Threatened, endangered, and sensitive species of the Intermountain Region. U.S. Forest Service, Intermountain Region, Ogden, UT.
Steele, B., F. Johnson, and S. Brunsfeld, eds. 1981. Vascular plant species of concern in Idaho. Forest, Wildlife and Range Experiment Station, Moscow, ID. 161 pp.

Allium madidum

Habitat

Reproduction

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