Herbicides are chemicals used to kill plants.
A chemical used to kill plants. These can vary from "kill everything" types through to selective types (e.g. broadleaf lawn weedkillers).
Herbicides are usually applied with water soluble sprays, but they can also be granular salts (eg. lawn "weed & feed" mixes; and copper sulphate) or solid (native copper can be an effective tree-killer).