You may expect this article to be about planting red, white, and blue flowers for the Fourth of July. For me, patriotic gardening is using American plants in your home landscape to provide food for American wildlife. The term American plants is synonymous with native plants.
The important difference between native plants and plants that originate in other parts of the world is their chemistry and how a plant’s chemistry relates to American insects. The massive number of insects is the key to transferring the sun’s energy from plants through the food web to higher forms of animals.
These insects are a major source of protein for wildlife from chickadees to grizzly bears. Parent chickadees do not feed their babies berries or sunflower seeds. They must find 400 to 575 caterpillars a day to feed their nestlings. These caterpillars are found primarily on native plants.
Over millions of years, our American plants and insects have worked out chemical relationships. Plants develop toxins such as latexes, alkaloids, terpenes, and tannins to make their tissues unpalatable. Over time, insects develop enzymes capable of breaking down these chemicals.
Plants from other continents have chemicals that most American insects cannot break down and thus cannot sustain them. A well-known example is the monarch butterfly. Its caterpillar stage of life can eat only milkweed, tolerating the toxins in the leaves and actually incorporating them into its body to make it safe from predation by birds.
Landscape plants from other parts of the world such as azalea, camellia, boxwood, crape myrtle, and ligustrum serve very little function for American insects and thus wildlife farther up the food web. They may provide nectar for a hummingbird or butterfly or berries for birds, but for the most part native insects cannot utilize these landscape plants.