Keystone plants are plants that feed the greatest number and diversity of insects. Like the wedge-shaped keystone that holds an arch together, keystone plants hold entire ecosystems together. Plants are, of course, primary producers that capture the sun’s energy and make that energy available to every other organism on Earth. Without plants, animals and fungi simply could not exist. Because animals and fungi must feed on plants for survival, many plants evolved elaborate chemical defenses to make them unpalatable or toxic to herbivores. Nevertheless, native insects have hundreds of thousands (often millions) of years of co-evolutionary history with native plants to overcome their host plants’ chemical defenses – making the sun’s energy available to a much wider diversity of life – including insectivorous birds, reptiles, amphibians, mammals. Without insects, the sun’s energy would not be able to cascade down the food web.
When exotic horticultural plants are introduced to North America, they generally leave behind their insectivorous predators, while native North American insects lack the co-evolutionary history required to metabolize their toxins. This is the reason so many exotic ornamental plants are “insect resistant” and also the reason such exotic plants have the potential to wreak havoc as invasive species. The lack of insect relationships turns areas dominated by invasive species into ecological deserts.
For this reason, it is critically important to include as many keystone plants as possible in your home landscape. Oak trees, for example, can support 500+ species of caterpillars (which are juicy hamburgers to birds)! Fortunately, there is now more than a decade of science underpinning the identification of keystone plants, which you can find on websites like Homegrown National Park and the National Wildlife Federation.
Native Plant lists and Butterfly Host Plants (mostly native)
Some of our members have been kind enough to compile and share lists of plants that do well in our area.