Kingdom: Plantae

Phylum: Magnoliophyta -- flowering plants

Class: Magnoliopsida -- dicots

Family: Fabaceae -- pea

Common Name: Canadian or Canada milkvetch

Species Code: ASCA11

Origin: The species is widespread over much of North America. The Palouse phase is usually var. mortonii, which has a much more limited distribution from open pine forests to sometimes in shrub-steppe of British Columbia, Washington, Oregon, Idaho, and Montana.

Rare: no

Form: forb, perennial, erect to decumbent, rhizomatous, 30-80 cm tall, not silvery pubescent.

Duration: perennial

Longevity: short

Habitat Type: prairie, forest

Wetland Indicator Status: FACW-

Leaves: Alternate, pinnately compound, 10-20 cm long; leaflets 13-29, ovate-lanceolate or elliptical, 1.5-4 cm long, glabrous above, lepidote beneath, 1-4 cm long, peduncles equaling or exceeding the leaves.

Mature height: 08-20 inches

Flowers: borne in a dense spike-like raceme, flowers drooping, corolla 12-18 mm long, greenish-white, yellowish-white or white, the wings as long as the banner, the keel frequently purple-tipped.

Flower color: white, pale yellow

Bloom: June, July

Bloom starts on: mid June

Bloom ends on: late July

Fruit: pods erect, crowded, 8-23 mm long, sessile, divided into 2 parts by the suture; seeds brown, 2 mm long, reniform.

Characteristics:
Worldwide, Astragalus is the largest genus of vascular plants, numbering around 2500 species. Around 400 of these occur in North America. Most are narrow endemic species specifically adapted to a particular set of habitat conditions (Hu et al 1999). A. canadensis, however, has a broad ecological amplitude. It ranges across northern North America and as far south as Texas. 3 varieties are commonly recognized, of which var. mortonii is the common Palouse species. It differs in lacking the silvery pubescence of the other 2 varieties, the plants appearing greenish rather than grey-green.
A. mortoni in St. John 1963, Piper & Beattie 1914.
Reproduces both sexually by seed and vegetatively by rhizomes.
120,000 seeds/lb (USDA NRCS PLANTS Database 2009).
n=16 for var. mortonii, n=8 for var. brevidens (Hu et al 1999).
Insect pollinated. Platt et al (1974) found an Iowa population to be mostly pollinated by bumblebees (Bombus spp.).
Flowers are perfect.
Flowers are self-incompatible (Platt et al 1974).
var. mortonii is a tetraploid while var. brevidens is a diploid.
The plants were used medicinally by some native peoples.
Fruit is a legume.
Some Astragalus species are toxic to livestock.
Larva of the clouded sulfur (Colias philodice), the silvery blue (Glaucopsyche lygdamus), the western tailed blue (Everes amyntula), and the arrowhead blue (Glaucopsyche piasis) butterflies feed on Astragalus species. While they prefer alfalfa, larva of the orange sulfur butterfly (Colias eurytheme) may also feed on Astragalus species (Pocewicz 2005). Larva of a snout weevil (Curculionidae: Tychiinae) feed on the seeds (Platt et al 1974).

Sun requirement: partial to full sun

Soil moisture: mesic

Precipitation: 20-50 inches for the species (USDA NRCS PLANTS Database 2009).

Fire: Some Astragalus spp. resist fire by having deep taproots and the ability to form new shoots from the taproot. The new shoots will produce seed the year following a fire (McLean 1969).

Hazards: Some Astragalus species are toxic to livestock.

Sowing time: fall or spring

Transplant time: spring

Stratification: seed should be scarified.

Seed yield: high

Seed harvest: July

Seed first harvest: second season

Seed cleaning: easy

Planting duration: short

Seed shatter: medium

Seed size: medium

Seed harvest date: July

Herbaria: Specimen data and digital resources from The Consortium of Pacific Northwest Herbaria

Propagation:
1 protocol in the Native Plant Network
University of Kentucky

Other Propagation Information:
Scarification increases germination (Sorenson & Holden 1974).
Scarification and cold, moist stratification increase germination (Greene & Curtis 1950).
Seed production is higher at higher plant densities (Platt et al 1974).
Reproduces both sexually by seed and vegetatively by rhizomes.

Notes: Astragalus canadensis seed needs to be scarified. It is one of the most widely adapted species of Astragalus. Weakly rhizomatous, blooms in June (Skinner et al 2005).

References:
Greene, H.C., and J.T. Curtis. 1950. Germination Studies of Wisconsin Prairie Plants. American Midland Naturalist 43:186-194.

Hu, Jer-Ming, Michael J. Sanderson, and Martin F. Wojciechowski. 1999. Website for the Largest Genus of Vascular Plants, Astragalus. University of California, Davis. Online at http://ginger.ucdavis.edu/astragalus/astragalus_home.htm Accessed 10/29/06.

McLean, Alastair. 1969. Fire Resistance of Forest Species as Influenced by Root Systems. Journal of Range Management 22:120-122.

Piper, C.V., and R.K. Beattie. 1914. The Flora of Southeastern Washington and Adjacent Idaho. Lancaster, PA: Press of the New Era Printing Company. 296 pp.

Platt, William J., Gerald R. Hill, and Suzanne Clark. 1974. Seed Production in a Prairie Legume (Astragalus canadensis L.): Interactions Between Pollination, Predispersal Seed Predation, and Plant Density. Oecologia 17:55-63.

Pocewicz, Amy. 2005. Host Plants of Palouse Butterfly Species. 2 page handout to accompany the April 2005 presentation to the Palouse Prairie Foundation.

Skinner, David M., Paul Warnick, Bill French, and Mary Fauci. 2005. More Palouse Forbs for Landscaping. USDA NRCS Pullman Plant Materials Center and Palouse Prairie Foundation. Online at http://www.wsu.edu/pmc_nrcs/Docs/More_Forbs_for_Landscaping.pdf

Sorensen, J.T., and D.J. Holden. 1974. Germination of Native Prairie Forb Seeds. Journal of Range Management 27:123-126.

St. John, Harold. 1963. Flora of Southeastern Washington and of Adjacent Idaho. 3rd edition. Outdoor Pictures. Escondido, CA.

USDA NRCS. 2009. The PLANTS Database (http://plants.usda.gov, 13 July 2009). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Links:
Plant Profile from the USDA PLANTS Database
Species information from the University of Washington Herbarium