Bird Food

What Are the Weeds Under My Bird Feeder, and Is It Palmer Amaranth?

Almost every bag of mixed bird seed carries weed seed, and the commonest passenger is pigweed. One fold of a leaf stalk tells you whether yours is the pigweed that state agriculture departments want reported.

The weeds growing under a bird feeder are almost always pigweeds, the Amaranthus group that includes redroot pigweed, smooth pigweed, waterhemp and Palmer amaranth. Their seed arrives in the bag. When weed scientists examined 98 commercially available bird feed mixes, 94 of them contained pigweed seed, and 27 contained Palmer amaranth seed specifically.

So the honest answer to "is it Palmer amaranth?" is: probably not, but often enough to be worth two minutes of checking. It turned up in more than one bag in four in that study, and it is the weed on this page that agriculture departments ask the public to report.

Why bird seed grows weeds#

Bird seed is grain harvested from fields, and seed from the weeds growing in those fields ends up in the bag. The researchers behind the 98-mix study, Oseland and colleagues, writing in Invasive Plant Science and Management in 2020, recommended careful weed control in fields grown for bird feed and sieving during packaging to cut the contamination.

They found seed of 29 weed species across the mixes. Besides the pigweeds, the list included common ragweed, kochia, foxtails, wild buckwheat, common lambsquarters and large crabgrass. Not every seed is alive: in their greenhouse test, roughly 19 percent of the pigweed seed was readily germinable. That still adds up. In one recalled bag of birdseed sold in Washington and Oregon, inspectors counted 200 Palmer amaranth seeds.

Then the feeder does the planting. Birds sort through a mix for the sunflower and flick the rest onto bare, disturbed soil. That rejected fraction is also what makes cheap mixes poor value, as worked through in seed mix vs straight seed.

Which ingredient brought which weed#

The study's most useful finding for anyone buying seed is that contamination tracked specific ingredients. Read the label of the bag you have been using against this table, and you can usually predict what is coming up under the feeder.

Two things follow. The grains that raised pigweed contamination are the same cheap grains that bulk out bargain mixes, so the bag that wastes the most seed is also the one most likely to grow pigweed. Checking the first three ingredients, as set out in bird seed mixes: reading the label, does double duty. And a single ingredient is not a weed-free bag: sunflower and safflower each carried their own weed. What a single ingredient changes is how much seed birds throw on the ground.

Is it Palmer amaranth? The checks#

Palmer amaranth looks a great deal like waterhemp and the common pigweeds. The Minnesota Department of Agriculture separates them with these checks:

1. Fold the leaf stalk. Fold the petiole, the stalk joining leaf to stem, back along the leaf blade. On Palmer amaranth the petiole is longer than the blade. Waterhemp, redroot pigweed and smooth pigweed all have shorter petioles. This is the most useful check.
2. Feel for hairs. Every part of a Palmer amaranth plant is smooth. Fine hairs on the leaf, petiole or stem mean it is not Palmer amaranth.
3. Look at the leaf shape. Palmer amaranth leaves are diamond shaped. Waterhemp leaves run from long and narrow to oval. Redroot and smooth pigweed leaves are round to oval.
4. Look for a chevron. Some Palmer amaranth plants carry a whitish V-shaped mark on the leaf. Not all do, so its absence proves nothing.
5. Check the seedhead, if there is one. A female Palmer amaranth seedhead can reach 2 feet (60 cm) long and is very prickly to the touch.

A plant that fails the first or second check is not Palmer amaranth; deal with it like any other weed. A plant with long petioles and no hairs at all should be treated as a suspect.

Why anyone cares about one weed#

Palmer amaranth is a serious farm weed: 6 to 8 feet (1.8 to 2.4 m) tall by Minnesota's description, more than 10 feet in the Washington report, and resistant to many herbicides. In the 98-mix study, five mixes held waterhemp or Palmer amaranth seed that proved resistant to glyphosate in a greenhouse screen. The ScienceDaily summary of the study puts that at one in 10 mixes; the paper's abstract counts five of 98.

Bird feeders have already carried it into new states:

• 2021, Montana. The state's first Palmer amaranth appeared directly beneath a bird feeder.
• August 22, 2025, Spokane, Washington. Plants were found in landscaping islands at a Safeway store, near where birdseed had been spread. Washington and Oregon then recalled Signature Pet Care Songbird Blend Wild Bird Food in 7 pound bags sold at Albertsons, Safeway and Haggen stores, after 200 Palmer amaranth seeds were found in a single bag.
• By February 2026. A Spokane County Noxious Weed Control Board inspector had identified seven more birdfeeds sold in Washington and Oregon containing Palmer amaranth seed. Four also held waterhemp seed, never before found in Washington.

Montana State University agricultural ecologist Tim Seipel put it plainly: bird feed "falls somewhere between our seed and our feed laws, so it can be dirtier than you would expect it to be."

If it passes the Palmer checks#

These steps follow what the Washington and Oregon agriculture departments told buyers of the recalled seed.

1. Photograph it first: the whole plant, a folded leaf showing petiole against blade, and any seedhead.
2. Pull it carefully straight into a black plastic bag, and put the bag in the trash, so no seed shakes loose on the way.
3. Bin the seed you were feeding. Double bag loose seed and put it in the trash, not the compost. Return any recalled product for a refund.
4. Clean the feeder before refilling it, using the method in how to clean a bird feeder.
5. Report it. In Minnesota, the Noxious Weed Program takes reports at noxiousweeds.mda@state.mn.us or through the department's online form. Elsewhere, contact your state department of agriculture or, where your state has one, the county noxious weed board.
6. Keep checking the spot. One plant means the bag carried seed, and more of that seed may still be in the soil under the feeder.

Stopping the next crop#

None of this means you should stop feeding birds. It means keeping seed off bare soil.

Feed foods with nothing to throw out. Single-ingredient foods that birds eat completely, such as sunflower hearts and the hulled foods in no-mess and hull-free blends, leave far less on the ground than a mix that birds sort through.

Put a tray under it. A catch tray wider than the feeder stops spill before it reaches the soil, and its contents go in the trash. Serve millet on a ground feeder or catch tray rather than scattering it. The tray also removes the nightly meal that brings rodents under bird feeders.

Scout the drop zone in summer. Walk the ground under and around each feeder every couple of weeks from late spring to the end of summer, and pull anything you cannot name while it is small. Weeds under a feeder are easy to miss because nobody expects a crop there. If you rotate feeder positions, as described in moving a feeder, keep checking the old spot too.

Treat the sweepings as waste. Hulls and spilled seed raked from under a feeder hold the same weed seed the bag did. The wider cleanup is in seed mess, hulls and dead grass.

What this page cannot tell you#

The 98 mixes were bought in 2016 and 2017. The figures show how common weed seed is in bird feed, not what is in the bag on your shelf today.

The checks above separate Palmer amaranth from waterhemp and the common pigweeds. They are not a general weed key; ragweed, kochia and the grass weeds need their own identification.

None of the sources tested hulled foods for weed seed. Hearts and hull-free blends reduce how much seed reaches the ground; they do not certify the bag clean. The tray and the summer walk are what catch a problem early.