"The more diversified the descendants from any one species become in
structure, constitution and habits, by so much will they be better enabled to seize on
many widely diversified places in the polity of nature, and so enabled to increase in
Although Charlie's prose was a little stiff, what I think he was trying to say was the more ecotypes or biotypes a weed species has (or the more species present in a field), the better it will be in taking advantage of opportunities left open by our weed management systems, and thus able to produce seed ensuring future survival. Charlie was no weed scientist, but he knew then what I want you to know now: weeds are diverse; their diversity allows them to have at least a few variants (if not many) in the seed bank ready to take advantage of any opportunities left open in our weed management systems. These opportunities mean crop losses, and more weed seed returned to that field.
Biodiversity within plants and weeds can be defined narrowly or broadly. Broadly, weed biodiversity includes genetic, somatic, habitat, temporal (time) and floral community diversity. To know more about habitat diversity go and look at the material in that section. Temporal diversity is covered in our section on weed life cycles.
To give you a favor of the biodiversity of one important weed, take The Foxtail World Tour.