I’ve been using the preemergent herbicide Preen (active ingredient trifluralin) to help reduce weeds in the rose garden. There are lots of forum posts about the use of trifluralin and oryzalin for controlled chromosome doubling of roses. These herbicides are not very water soluble and when put on the soil they interfere with cell division in the upper crust of soil stunting and killing germinating weed seeds.
Over the years it is interesting to find what appears to be chromosome doubled weeds- seedlings that didn’t die, but may have been stunted by the chemical and grew out of it as a doubled plant. I wonder if we looked closely in gardens where preen was used what the rate would be of finding doubled plants of volunteer seedlings of desired plants. I wonder too what examples we could find of unintended ploidy manipulation of weeds or native plants and how that may alter competitiveness/fecundity/crossability, etc. of them in natural settings.