Provide Them a Good Meal
Monarch butterflies cannot survive without milkweed. The leaves of these native wildflowers are the only things their picky caterpillars will eat. If a Monarch accidentally lays its eggs on another plant, like the similar-looking but invasive dog-strangling vine, the caterpillars will not live.
Monarchs have evolved with milkweed. The caterpillars have developed an immunity to the toxic sticky white sap the leaves produce. The toxin even stays in their body as they grow and helps protect them from predators.
Milkweed is the Monarch’s host plant. There are three species of milkweed native to the watershed: Butterfly, Swamp and Common. Like the Monarch, many other moth and butterfly caterpillars have host plants of their own. The Great Spangled Fritillary only feeds on violets, and the Coral Hairstreak only eats plants in the genus Prunus, like Choke Cherry and Black Cherry. The Eastern Tiger Swallowtail and the Red Spotted Purple, on the other hand, feed on a variety of trees including oaks, willows and birch.
Some host plants support only a few caterpillar species, while others can support a great number. Milkweed supports 12 different caterpillars, for example, whereas oak trees can support 521 different species found in Southern Ontario.
Native host plants aren’t just important for butterflies. They’re also important to the animals that rely on caterpillars for food. If you’re a hungry bird scouring the leaves of our native Sugar, Red, or Silver Maples, you would likely find an abundance of caterpillars. If you landed in a non-native Norway Maple, you may find only one.
Some birds need thousands of caterpillars to raise one brood. Choosing to grow native host plants will not only attract butterflies to your yard, but also support a diverse and resilient landscape.