"Noxious" weeds are so called because they are harmful (from the Latin, nocere, to harm). But harmful to whom and using what criteria to measure damage? Since in the broadest sense, quite a variety of unwanted plants can be so classified, I try to approach the subject from a number of perspectives in these pictures.
For instance, some people use the terminology "noxious weeds" as if it were almost synonymous with "invasive plants." And what criteria is used to measure the damage caused by invasive plants? Well, here are two sets of criteria:
- The amount of money wasted by farmers in trying to battle such noxious weeds, as they encroach upon farm land
- The number of native plants threatened as such noxious weeds encroach upon their wild habitats, out-competing them for resources
In either of those 2 cases, after enough data is in, the noxious weeds in question will end up on one of the popular plant "blacklists," often organized by state (in the U.S.). Some states have even banned the importation of certain invasive plants, including Oriental bittersweet.
But there are other senses in which unwanted plants may be classified as "noxious weeds." To name just 3 of them:
- If they are poisonous plants
- If they are plants that cause rashes
- If they cause allergies, as does common ragweed.
Use the pictures of noxious weeds presented on the following pages to aid you in identification. On Page 2, we'll start with a noxious weed that causes allergies....