Types of Competition
Exploitative: Competition between two species through the effects they both have on the same resource
Interference:When competitors aggressively defend resources from others
Allelopathy: Chemical competition, i.e. toxic chemicals in plants
Resembles exploitative or interference, but represents the result of different mechanisms, i.e. consumption and pathogens
A personally relevant example: garlic mustard! I've been pulling it up in wooded areas and neighborhoods where I live, and I had done research, and it in fact has an allelopathic chemical, and the deer do in fact ignore it.