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Is Your Bird Feeder a Weed Seeder?

Consumers encouraged to take simple steps to protect farms and gardens

Are weeds sprouting beneath your backyard bird feeder? If so, researchers say the type of feed you use may be to blame.

In studies at Oregon State University, scientists examined 10 brands of wild bird feed commonly sold in retail stores. The samples contained seeds from more than 50 weed species – including 10 ranked among Oregon’s most noxious weeds. Each brand tested contained weed seeds, with six different weed species found in half or more of the samples.

“Once a weed seed drops from the feeder to the ground and sprouts, it has the potential to flower and spread,” said Dr. Jed Colquhoun, associate professor at the University of
Wisconsin – Madison, formerly with Oregon State University. “In fact, when we informally questioned landowners and farmers to investigate the spread of a relatively new weed in the Pacific Northwest – velvetleaf (Abutilon theophrasti) – we found it is growing in the soil beneath backyard bird feeders.” In a short-term study of what happens when stray bird feed drops to the soil, about 30 weed species sprouted in just 28 days. Between three and 17 weed species grew from each of the 10 brands of feed tested.

So how can you minimize the spread of new or invasive weeds that originate in bird feed? There are several simple strategies to consider:

  • Use a tray attachment under your feeder to keep seeds off the ground.
  • Select foods that won’t sprout, such as sunflower hearts, peanuts, peanut butter, raisins, mealworms and plain suet cakes.
  • Look for treated wild bird food mixtures. Many manufacturers are now baking their products to kill weed seeds, using guidelines established by the U.S. Department of Agriculture. So read product labels carefully to make certain you buy a treated brand.
  • Keep an eye out for weeds under your feeder and pull them before they can flower and spread.
  • If you use a wild bird food blend that contains a variety of seeds, contact the producer or talk to your local retailer to discuss what measures are taken to ensure the product is free of invasive weed seeds.

Jed Colquhoun was lead researcher for the bird feed study in cooperation with Carol
Mallory-Smith, a professor at Oregon State University. The work was funded by the Agricultural Research Foundation at Oregon State University.

About the Weed Science Society of America:
The Weed Science Society of America, a nonprofit professional society, was founded in 1956 to encourage and promote the development of knowledge concerning weeds and their impact on the environment. The Weed Science Society of America promotes research, education and extension outreach activities related to weeds, provides science-based information to the public and policy makers, and fosters awareness of weeds and their impacts on managed and natural ecosystems. For more information, visit http://www.wssa.net.


Ten Noxious Weeds Found in the Bird Seed Evaluated in the Oregon Study:

Buffalobur (Solanum rostratum Dunal)
Bull thistle (Cirsium vulgare)
Canada thistle (Cirsium arvense)
Common ragweed (Ambrosia artemisiifolia)
Dodder (Cuscuta spp.)
Field bindweed (Convolvulus arvensis)
Jointed goatgrass (Aegilops cylindrica)
Kochia (Kochia scoparia)
Puncturevine (Tribulus terrestris)
Velvetleaf (Abutilon theophrasti)