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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Publications at this Location » Publication #170702


item Harmon, Daniel - Dan
item Young, James

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/30/2004
Publication Date: 2/7/2005
Citation: Harmon, D., Young, J.A. 2005. Germination of Mexican whorled milkweed [abstract]. Weed Science Society of America. 45:119.

Interpretive Summary:

Technical Abstract: Mexican whorled milkweed (Asclepias fascicularis) is one of the most important species of concern in the Asclepias genus. This native but poisonous species is a ruderal species, spreading to fence runs and abandoned farmlands. It is now considered a valuable component of the western landscape because of its heavy use by butterflies, bees, and other insects. Mexican whorled milkweed is a perennial species. Establishment can occur by seed dispersal or vegetative propagation. Our purpose was to investigate seed germination of Mexican whorled milkweed at a wide range of constant and alternating temperatures. Seeds were incubated at 55 constant and fluctuating temperatures and the results were used to calculate quadratic responses. Mexican whorled milkweed germinates in warm temperatures from 30 through 40 C. Very little to no germination occurred at cooler temperatures. This germination strategy favors warm season establishment possibly aiding in avoiding interference from winter annual weeds. Mexican whorled milkweed's unique pattern of warmer temperature germination with a drastic decrease as the incubating temperature decreases warrants further seed ecology research. Future efforts should include examining cold dormancy, osmotic potentials, and root propagation.