Anyone who feeds birds in the backyard has had the experience of weeds -- even tiny sunflowers -- popping up in the grass beneath the feeder. Usually they're readily mowed down. But you need to watch out, says the Weed Science Society of America (WSSA), because some of those weeds can be pretty aggressive.
In fact, when researchers at Oregon State University looked at 10 brands of wild bird feed commonly sold in retail stores, they found that they contained seeds from more than 50 species of weeds. including 10 that are on their state's list of most noxious weeds.
Not all of them grew, but plenty did. When they studied the weed seeds that fell to the ground beneath bird feeders, Dr. Jed Colquhoun and the other researchers found that "30 weed species sprouted in just 28 days. Between three and 17 weed species grew from each of the 10 brands of feed tested."
The 10 noxious weeds were buffalobur, bull thistle, Canada thistle, common ragweed, dodder, field bindweed, jointed goatgrass, kochia, puncturevine , and velvetleaf (a relatively new weed in Oregon that was found mostly growing under bird feeders).
So how can you minimize the spread of new or invasive weeds that originate in bird feed? There are several simple strategies to consider to avoid having your bird feeder become a weed seeder, the WSSA says:
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.
Buy only treated wild bird food mixtures. Many manufacturers are now baking their products to kill weed seeds, using guidelines established by the US Department of Agriculture. So read product labels carefully to make certain you select a treated brand.
Keep an eye out for weeds under your feeder and pull them before they can flower and spread.