Weed Wisdom Feb. 2018

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Russian thistle

with files from Dr. Charles Geddes

Russian thistle could come back to Alberta through glyphosate-resistant biotypes coming from northern United States

 Alberta weed watchers are alert for Russian thistle because a glyphosate-resistant biotypes showed up recently in Montana (in 2015) and Oregon (in 2016).  Russian thistle dropped to 27th most abundant weed in Alberta since 1980, but in fall 2017, Hugh Beckie (AAFC, Saskatoon) led a post-harvest kochia and Russian thistle survey in Alberta because he expects these biotypes to move into Alberta. Results of Beckie’s survey should be out this spring.

Russian thistle is an annual weed that spreads via seed distributed by a tumbleweed.  The plant has a red stem and long needle-like leaves. It can be a meter tall and gobbles nitrogen from the soil. It is drought tolerant. In fact, New Mexico State University researchers determined that “Russian thistle is one of the most efficient plants in the world at creating biomass per unit of water used.”

Russian thistle flowers

The plant has spine-tipped leaves and is bristly when mature. Its seeds are brown/grey, cone shaped and 2mm long. The flowers are unspectacular and bloom close to the leaf axils. Russian thistle can germinate at a wide range of temperatures and supports some agricultural insect pests.

It is best to control it by mowing prior to flowering or early season chemical control.

Be on the watch for this weed, control it and report it to local weed inspectors.