We all know planting natives is great for wildlife, but are some plants better for the environment than others? As a source of food for over 450 insects, common milkweed is at the top of the list.
Butterflies, moths, bees and wasps have all adapted to use milkweed for sustenance. Some of these insects have even learned to use the plant’s toxicity as a survival technique.
All milkweed species contain cardigan glycosides, organic compounds that make them toxic in large quantities for many species. However, several insects have evolved to not only be able to consume milkweed but become toxic to predators once they do.
Insects who take part in this survival technique have evolved to have similar physical features. If you sit and watch the insects on a milkweed plant, you will notice that many of them, although different in size and shape, have patterns of orange and black. Known as Müllerian Mimicry, the colors act as a warning sign to predators that they contain toxins. Examples of this coloring can be found on monarch butterflies, viceroy butterflies and milkweed bugs.
Although all milkweed species contain some of the toxic compounds, they don’t all have equal amounts. Species found in the southern United States tend to have much higher concentrations than those in the north, but regardless of toxicity levels found in each species, the bright orange coloring tricks predators around the country.
The monarch butterfly is the most popular of these insects and is known for evolving to exclusively use milkweed as a host plant. The caterpillars of the monarch butterfly can only eat milkweed. This relationship with the milkweed plant keeps monarchs safe from predators, but as milkweed has become less common due to development and overuse of herbicides, the monarch populations have suffered.
In the past 30 years, the monarch butterfly population has declined by 88%. In 2020, the U.S. Fish and Wildlife Service determined that monarchs are in need of endangered species status, but have not yet been listed due to work on higher-priority listings. Monarchs can travel up to 3,000 miles during their fall migration and need habitat covering the entire length of their migration routes to fuel their journey.
Planting more milkweed for caterpillars and more nectar plants for adult butterflies can have a dramatic impact on supporting monarch butterflies and other insects. Every plant counts and home gardens can serve as a bridge between larger areas of habitat. Planting the correct regional species or milkweed and other native wildflowers is particularly important for helping wildlife. Before planting, check to find the species of milkweed that grow in your area and the appropriate nectar plants. One of the best things about adding these plants to home gardens is that they continuously bloom throughout the season so they are beautifying the landscape while providing long-term benefits to wildlife.