We like to put plants into categories. Categorizing a plant under one of the above categories can help us decide if we want to add that species to our yard or not. Understanding how a category is defined can help give meaning to the label. Additionally, knowing that the label is subjective to the experience of the gardener can add flexibility to your choice of plants.
A native plant is a species that is local to this area. Native can be subject to how large of an area one considers to be local and what period of time we are looking at. Usually the area considered is the state of Missouri and the time period is when European settlers first came to the area because that is the first detailed record available of the flora. However, in the St Louis area it makes more sense to consider east central Missouri and west central Illinois to be the local area.
Exotic plants are non native plants. Many exotic plants can not withstand our climate and die during the winter. An exotic plant is also a plant out of place, one without natural predators. Exotic plants that are able to handle the extreme climate of Missouri often earn the title exotic invasive because they take over our natural areas without any control to stop their reproduction.
The invasive plant is the type to avoid. Being categorized as invasive is a big warning label that you do not want this plant in your yard. Even if you have an invasive plant in your garden that is well behaved it still can be harming natural areas if a bird picks up a seed and deposits it in a new place. Invasive plants are the biggest environmental threat to our existing nature reserves. Stop the spread of invasive species by eliminating them from our home gardens and educating friends and neighbors to do the same.
Aggressive plants can be garden worthy if they receive enough care. Aggressive plants are often found in nature colonizing recently disturbed sites. They are the healers of natural areas and give way to more established plants over time. In our gardens aggressive plants can be problematic because a garden area is constantly being disturbed with our obsessive tinkering. Methods for gardening with aggressive plants include dead heading, root barriers, isolation, keeping low in the watershed, and pairing with equally aggressive plants. Limit opportunities for seed dispersal and root travel. Be careful to keep your composting area clear of viable plant parts. Categories like aggressive can be very subjective to the experience of the gardener.
Well stated, Besa. I learned much in your paragraph on aggressives.