Plant Origin Terms, by Bill Stringer.
Reprinted from the Journal of the South Carolina Native Plant Society, and used by permission.

Native plant – A plant species that is found in a region because it developed and evolved in that region over thousands of years. Plants that existed in a region prior to settlement.

Exotic (introduced) plant – A plant species that exists in a region because it was brought to that region by man, during and since settlement of the region. We are still introducing exotic plants, by intention or by accident.

Naturalized plant – An exotic plant that was introduced into an area, escaped from cultivation and reproduces on its own (includes exotic invasive plants). Many plants commonly thought to be natives were actually introduced by early settlers.

Exotic invasive plant – An exotic plant species that is able to invade and overrun native ecosystems. Some native plants can become invasive under certain conditions, but most invasive species are introduced (exotic).

Ornamental plant – A plant species or cultivar that is grown for its beauty (in its end use), rather than commercial or production reasons.

Variety – Within a species, a naturally occurring sub-group of plants that have one or more minor characteristics that set it apart from the rest of the species. Ex.: Solidago odora var. chapmanii.

Cultivar – Short for "cultivated variety." A plant “variety” developed by man via plant selection and/or genetic manipulation to exhibit a set of plant characteristics. Cultivars are maintained via controlled pollination or vegetative means, so that cultivar characteristics are passed to ensuing generations.

Ecovar – Short for “ecological variety.” A plant “variety” developed by man from a collection of plants of a native species that were selected from several to many natural populations in a specific region. The purpose is to have high genetic diversity in the parent collection, that reflects the natural diversity within that species in the defined region. To maintain genetic diversity in ensuing generations, little to no selection is done during the ecovar development process. An ecovar is an intermediate step between a wild-growing plant and a cultivar.

Source-identified seed – Off-spring of plants collected from a single defined natural population of a native species for production of seed. No selection is done during the collection and subsequent seed increase steps, so as to conserve genetic diversity. The genetic diversity is less than for an ecovar.

NOTE: Cultivars, ecovars, and source-identified seed are usually "named," and that name is used to denote any plant material subsequently marketed from these seed parent sources.