Naturalized plants are plants that have become established as a part of the flora of a locale other than their place of origin. So to qualify for such status, two conditions must be met:
- The plant in question must be foreign ("exotic," "introduced," and "alien" are other names used to indicate that a plant is of foreign origin).
- It must be able to grow on its own and propagate itself, without human aid (for example, without any artificial irrigation, fertilizing, dividing, pest control, weed control , etc.). That is, it becomes a wild plant in its adopted homeland. Not all plants introduced from foreign lands are tenacious enough to naturalize.
When a plant naturalizes in an area, this can be either a "good" thing or a "bad" thing, depending on your opinion of the particular plant.
Matter of Perspective: Free Plants Versus Invasive Plants
For instance, when we buy exotic bulb plants (such as the tiger lily) that have pretty flowers and plant them in our gardens, we, personally, may be delighted if these beauties become naturalized plants and spread, because that means more flowers to admire -- and for free. Likewise, gardeners have been mesmerized for decades by the magnificent fall foliage of burning bush, turning a blind eye when the plant starts spreading into the forest and getting along just fine without human aid.
But other people may come to a very different conclusion about such plants, regarding them as nuisances -- or worse. That is because, sometimes, alien plants that become naturalized plants are vigorous enough to spread out of control -- in spite of our attempts to control and/or eradicate them.
Such naturalized plants tend to acquire a pejorative designation: namely, "invasive." The naturalized plants in these cases can end up crowding out native, or "indigenous" plants. Organizations exist whose sole purpose is to lobby for action against invasive plants. But not all naturalized plants become invasive plants.
Naturalized plants can be grouped in a number of different categories; I furnish some examples pertaining to the North American continent in the lists below (in addition to the tiger lilies and burning bushes already mentioned). Note that, to make such a list, it is enough that the plant has naturalized in just certain parts of North America (that is, not all of these examples have naturalized in all regions of the continent).
Some naturalized plants are generally classified as weeds, which is, of course, a subjective term, as highlighted by the famous definition of "weed" advanced by Ralph Waldo Emerson. It is important to understand that not all of the following are necessarily noxious weeds. Many people, in fact, think of dandelions, for example, as being an herb:
Some of the perennials in this list are invasive, others are not. Research each plant before you begin growing it to determine what its status is in your area:
- Black-eyed Susans
- Yellow flag (Iris pseudacorus)
- Blue flag
- Hens and chicks
- Lenten rose
- Oriental poppies
- Vinca minor ground cover
These spring bulbs can sometimes naturalize in grassy areas. Snowdrops and Scilla bloom so early in the spring that their flowers have come and gone before the grass has even put on any height:
Shrubs and Vines
These plants are invasive. Because of their size, it is hard to miss the impact that they have had on the wild North American landscape:
To conclude and sum up, remember that, while all invasive plants are, by definition, also naturalized plants, not all naturalized plants are invasive plants.
A related distinction to keep in mind is that between "native plants" and "wildflowers." The latter is often used to indicate any plant growing wild that has pretty flowers. But not all wildflowers are native plants; some are naturalized (or even invasive).