Yup after the floods of 93 I had problems with Cockle Burrs in a bottom field with a creek through the middle. I never had cockle burrs before.
Couple of years latter I was 2 miles upstream hunting. The field was loaded with cockle burrs.
I then knew where all my cockle burrs came from a couple of years earlier.
I am still fighting those damn cockle burrs.
They like to come up late as well.