Last week, the International Union for the Conservation of Nature (IUCN) added the iconic monarch butterfly to their list of endangered species, and our friends at KGW8 News stopped by to talk to our pollinator expert, Sara Finkle, about their plight. You can watch the video with Sara here, then keep reading to learn more about these fascinating pollinators and what we as gardeners can do to support them.
Although monarch butterflies aren't the most common sight in Portland gardens, Oregon is certainly on their migratory route. And this migration is part of what makes these butterflies so special in the first place! North American monarchs are one of the few insects known to make a long-distance annual migration — a trait far more often associated with birds. And in fact, there are two distinct populations of butterflies that make these trips. The better-known eastern population moves between Mexico and Canada each year, but the monarchs that visit Portland are part of a western population that spreads throughout the states west of the Rockies before retiring to eucalyptus groves in California each winter.
Part of the reason for monarchs' peril is the destruction of important habitat across their migratory range. While adult monarchs, like most butterflies, can feed on most any nectar-rich flower, the same can't be said for their larvae, which eat a diet of 100% Milkweed leaves. While these leaves are toxic to many other insects, monarchs have evolved to not only overcome these plants' chemical defenses, but to put these compounds to use for themselves: The cardenolides they ingest actually make them toxic to predators! Their orange and black coloration coloration warns birds not to make a meal of them, and the association is so strong that other species of butterfly have evolved to mimic their appearance in order to enjoy the same benefit.
Although this strategy is an evolutionary marvel, it comes with a tradeoff: Monarchs are reproductively tied to their host plants. Although there are many Milkweeds in the genus Asclepias native to North America on which monarchs can successfully lay eggs and reproduce, many hail from prairies and meadows — areas that have been largely converted to agricultural use or that have been tarnished by long-term pesticide and herbicide applications.
This leaves monarchs vulnerable because they require access to stands of milkweed all along their migratory route in order to sustain their numbers. You see, their migration is a multi-generational trip: The butterflies that return to California in the winter are the grand-children and great-grandchildren of the ones that left in the spring! But if an adult butterfly fails to locate a suitable host for its larvae, it cannot successfully reproduce. Without successive generations to continue this epic journey, the cycle is broken.
If you want to help monarchs in your own backyard, plant Milkweed in your pollinator garden, and encourage others to do the same. Adult butterflies will benefit from other floral sources of food, but the Milkweeds are the key to reproductive success. With this, learn to recognize their distinctive striped caterpillars and be tolerant of a little damage to your milkweed patch when you find them. (It's for a good cause!) And as always, you should avoid pesticides and herbicides whenever possible — even organic remedies have the potential to harm butterflies and their larvae.
When choosing a Milkweed for your garden, there are many species and varieties available in the Nursery trade, but the best option is almost always the native one. There are several Asclepias species that grow in our region, but the most commonly cultivated is the Showy Milkweed (Asclepias speciosa). For gardeners in other regions, a quick internet search will reveal species native to where you garden. Together, we can support migratory monarchs and help their numbers rebound!
To learn more about the plight of monarchs, you can view the full original article from KGW8. And for more tips on making sure your garden meets the needs of your local pollinators, be sure to check out Sara's six tips for pollinator gardening. (Images of monarchs courtesy of the Midwest Region of the U.S. Fish & Wildlife Service.)