When non-native or exotic invasive plants are introduced to an area and have no natural predators, they can displace native species. Many of these were intentionally brought to North America as ornamentals from other continents. They often have attractive flowers, foliage, or fruit, but “invasives” disrupt natural ecosystems, wildlife food sources and habitats, water flow, and soil health. Invasive exotic plants may also produce lots of seeds that can spread into woodlands. Some examples are Callery/Bradford pear, Chinese privet, Chinese and Japanese wisteria, and Chinese elm. Others produce a thick canopy and shade out native species or substances that prevent seed germination, like Asian Honeysuckles and Oriental Bittersweet.

In the past we gardened for food consumption, then aesthetics. Now, with changing climate and loss of habitat beauty alone should not be the only justification for selecting a plant for the landscape. Native shrubs, vines, and trees support insects, such as adults and larvae of beetles, butterflies, moths, ants, and flies. Certain insects depend on native flora as hosts for the larval stage and the berries and seeds for adults. Studies have shown that birds need a lot of insects to feed and fledge their chicks, with at least 70% native vegetation. Food webs depend on plants for energy, oxygen, and carbohydrates. Decomposing leaves build soil; the leaf litter and humus are essential to the microbes that recycle those nutrients.