It doesn’t take much for a Palmer pigweed to come back from the dead – or at least from what you consider to be its demise. To say that it’s tenacious is an understatement.
Compared to other weeds, Palmer possesses an immense ability to regrow from what seems to be almost nothing. Even worse, it can still generate plenty of viable seed that will bedevil farmers well into the future.
One University of Georgia study examined what are termed “hand-weeding failures” where enough of the plant remains in the field to rebound before the end of the season. The study shows just how strongly this weed wants to survive.
In the project, researchers waited until Palmer began to flower in cotton plots. At that point, they cut back a sample of Palmer pigweed to 3 heights – at the soil line, about an inch above the soil line and about 6 inches above the soil line.
That was 8 weeks after the cotton had been planted, and the team monitored weed height for up to 6 weeks after the cutting. After cotton was defoliated, seed were collected from the surviving female plants.
In a nutshell:
Close clipping did matter. The closer to the ground the weeds were cut, the fewer survived. However, even with cutting at ground level, 5% of the weeds made it through. Where stems were slashed at one inch above the soil surface, 36% survived. At the 6-inch cutting height, 65% made it through.
Survivors still managed to gain height. While surviving plants clipped at ground level grew less than an inch, those cut at 6 inches and 1 inch grew to heights of 40 inches and 15 inches, respectively. The uncut check plants reached 86 inches.
Seed production continued. Plants cut at 6 inches and 1 inch still produced 100,000 and 35,000 seeds, respectively. Even those cut at ground level still managed to eke out 700 seeds per plant. Uncut plants averaged about 400,000.
Seeds remained viable. Despite their mother plant’s rough life, seed across all treatments had a mean germination rate of 76%.