Working together to strengthen and support noxious weed management efforts in Montana.

Weed of the Week – Sulfur Cinquefoil

Wednesday, October 6th, 2010

Sulfur cinquefoil was introduced into North America in the 1900’s.  It began by populating eastern Canada and the Great Lakes region in the U.S.  In 1947, sulfur cinquefoil was discovered in Ravalli County, this was the first sighting in Montana.  Since the 1980’s, the sulfur cinquefoil population has exploded across the west.  This weed has been reported in 33 counties in Montana and occupies approximately 278,000 acres with in the state.

Concerns This weed is adapted to a variety of environmental conditions, it can grow in grasslands, shrubby areas, open forests, roadsides, ditches, and logged areas.  It often grows in association with spotted knapweed.

Sulfur cinquefoil is not very palatable to grazing animals.  Therefore, in grasslands where this weed occurs grazing will further reduce native grass production.  A sulfur cinquefoil plant has the ability to produce up to 1,650 seeds per year.  This plant can completely take over a site, creating a monoculture of sulfur cinquefoil.

Identification Sulfur cinquefoil is most recognizable for its yellowish green palamate compound leaves. The 5-7 leaflets are serrated and look similar to marijuana leaves or native strawberries. The plant is 12-28 inches tall and the stem is covered in sparse course, stiff hairs.  The flowers of this plant have five, pale yellow petals.

Sulfur cinquefoil is a long-lived perennial that has been documented to live up to 30 years.  Sulfur cinquefoil can be confused with the native northwest cinquefoil.  They can typically be differentiated among by the backside of their leaves.  The native cinquefoil has a silvery-green back side, where the non-native is green.  Also, the hair on the stem of the native lays flat against the stem and the non-native has hair that is stiff and perpendicular to the stem.

What can you do? As with any weed management there is no one solution, sulfur cinquefoil is best managed by integrating multiple controls.  An effective mechanical method for removing sulfur cinquefoil is hand digging or chopping the root crown out of the ground.  Cultivation on crop grounds is also an effective method of removal.  There have been a variety of herbicides that have proven to be very effective on controlling sulfur cinquefoil infestations.  It is important to revegetate once the sulfur cinquefoil has been removed.  There has not been any effective form of bio-control discovered yet because it is closely related to some of our native plants.  Getting infestations of sulfur cinquefoil under control takes time and diligence on the part of the landowner.  Please call your local weed district, with any questions regarding infestations on your property.

Visit the MWCA Weed ID pages for additional information and pictures of sulfur cinquefoil.

This series of articles was developed by Ravalli County.  If you would like to use these articles please contact Ravalli County Weed District Weed Coordinator at (406) 777-5842.


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