Brandon Smith (Redwoodtwig)
There are several kinds of plants which are out of harmony with either the natural plant population of the area or not in harmony with human usage.
The Missouri Department of Conservation has an excellent article on problem plants and animals in this part of the country.
Invasive species are the worst, threatening to turn the place into a mono-culture. Heading the list of those on this place are winter creeper, bush honeysuckle, and multiflora rose.
Some of the thorn bearing plants may be bothersome to humans, but worth their presence for food or as protective borders around less well defended food plants.
I'm not sure what outputs poison ivy provides to the local ecology, but it certainly does thrive in some areas. In other areas, where I expect people to visit, I treat it like an invasive species and get rid of it.
Bush Honey suckle and poison ivy, when young, under a half inch stalk, can usually be pulled up by the roots. Lay the pulled up plant so the roots are up in the sun and dry out. DO NOT throw poison ivy on a fire!
The basic control is to cut the larger ones close to the ground and apply one of the herbicides in strong concentration directly on the freshly cut stem. Carefully.
I've also found that bush honeysuckle will die if after cutting a big one close to the ground, completely cover it so no light can get in. Takes longer than poison. I've found a pair of standard gallon size plastic plant pots slipped together so no light shows inside works well.