Just think of Palmer amaranth as the Johnsongrass of the 1980's before effective herbicides came along, only on steroids. Or you can think of it as the "pigweed species that ate Chicago," a take on the old science fiction myth "the tomato that ate Chicago."
Compared to Johnsongrass of 30 years ago, Palmer amaranth is at its worst so far in Indiana in the northwestern counties, and in some other counties across northern Indiana. It's also showed up in pockets elsewhere, and in southwest Indiana. Farmers in southwest Indiana also felt the brunt of dealing with Johnsongrass all those years ago.
The problem with Palmer amaranth is many-faceted, but one trait that causes headaches is its ability to produce thousands upon thousands of seeds per plant. Once mature, the seedhead can easily be 20 inches long, much longer than the seedhead of other pigweed species.
If someone thinks they will mow down Palmer before it goes to seed and therefore prevent further spread, there's a twist that makes mowing a poor strategy.
In the coffee shop, it is known as Palmer pigweed. In university circles, it is referred to as Palmer amaranth. Whatever you want to call it, this weed is the No. 1 weed to watch. Stay on top of your control plan with our new free report, Palmer Amaranth: Understanding the Profit Siphon in your Field.
Kelly Barnett, regional manager for DuPont, recently demonstrated that Palmer amaranth plants that are only a couple feet tall, and half-grown, can begin to form seedheads.
"They can be several inches long even at a young stage," she says. "And once they form, they begin making seeds right away. I've found viable seeds in some of those seedheads on relatively small Palmer plants, compared to what they will be in size at maturity.
"If you wait to knock them down until when plants are bigger, the likelihood is that you've already allowed some to go to seed and drop seed. The volume of seed produced won't be as great as if the plant matures and has a full seedhead, but you still would be adding to the seed bank."
Seeds are small and plentiful. They are one reason the plant is hard to eradicate.