The Four-leaved Milkweed is a perennial plant that is one of the smallest in the milkweed plant family. This plant grows up to only 80 cm tall, with four light green leaves that grow in opposite pairs. They also grow clusters of small, white-pink flowers at the top of their stems. Seed pods are brown and narrow, and they have tufts of silky white hairs for wind dispersal.
Habitat and Biology:
This species is found in North America, but it is only restricted to the Eastern United States in two distinct regions, with its northern range only extending up into southern Ontario. The far eastern region in the United States ranges from Alabama, Georgia, and South Carolina up to eastern Indiana, Ohio, Pennsylvania, and New York. The slightly more western region can be found from eastern Oklahoma and western Arkansas northward through Missouri, western Illinois and eastern Iowa. In Ontario, there are only two known populations, both of which occur in Prince Edward County. Historical populations occurred in the Niagara River gorge area, as well as up into eastern parts of The Land Between in Lennox and Addington County.
The Four-leaved Milkweed species prefers habitat that was once fairly common throughout North America, but since colonization, agricultural booms, and urbanization, this habitat is now rare. The Four-leaved Milkweed prefers dry, open, rocky, and Oak-Hickory tree dominated deciduous forests. The two populations in Prince Edward County can be found on shallow soils with flat or gently sloping areas near steep limestone escarpments. They are in open and relatively dry forests dominated by Bur Oak, Shagbark Hickory, Ironwood, Easter Red Cedar, Sugar Maple, Basswood, and White Ash trees. These areas also have a fair amount of shrubby understories with Dogwoods, Juniper, and Sumacs.
Milkweed species reproduce only from seeds that are dispersed in the wind or by disturbance. Seeds do not last long in the soil and must germinate quickly in order for this species to survive. Plants are slow to mature, only reaching about 10 cm in the first 3 years of growth. Plants must reach about 33 cm in length in order to be able to produce seeds, which can take anywhere from 7 to 10 years. In order to produce viable seeds, the Four-leaved Milkweed must be pollinated by flying insect species such as bees, wasps, butterflies, and moths.
Conservation and recovery strategies:
The long-term goal for recovery of this species is to protect the two populations currently in Ontario, and re-establish new populations where possible. The Government of Ontario aims to identify and protect current populations through stewardship and conservation efforts, prioritize important research, implement a long-term monitoring program, confirm known and potential threats, develop Best Management Practices (BMPs), reintroduce populations to their historical ranges, and develop communication and education programs.
Government of Ontario. 2014. Four-leaved milkweed. Retrieved from: https://www.ontario.ca/page/four-leaved-milkweed
COSEWIC. 2010. COSEWIC assessment and status report on the Four–leaved Milkweed Asclepias quadrifolia in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. x + 40 pp. https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/four-leaved-milkweed-2010.html
Government of Ontario. 2018. Four-leaved Milkweed Recovery Strategy Executive Summary. Retrieved from: https://www.ontario.ca/page/four-leaved-milkweed-recovery-strategy-executive-summary
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