As we dream of our summer gardens, it’s time to consider adding some milkweeds. Milkweed flowers look like something from another planet: Sputnik-like bundles of little blossoms with curved prongs in pink, orange, purple and white. At least five milkweed species connect Flagstaff to the annual migration of monarch butterflies up and down North America. In fact the Southwest Monarch Study pinpoints Flagstaff as a “monarch hotspot.”
Butterflies are universal symbols of hope, transformation and joy. Monarch butterflies are especially inspiring, as millions of these fragile creatures complete their astonishing migrations over thousands of miles each year. They have a practical purpose, too, as vital pollinators of asters, goldenrods, native thistles and many other plants.
Monarch migrations begin on the coast of California and in central Mexico, where the butterflies have spent seven months or more overwintering in a state of suspended animation called diapause. With spring they revive, mate, and flutter north and east to find milkweed plants on which to lay their yellow eggs. These adults die soon afterwards but after four days, their caterpillars hatch.
All caterpillars are eating machines that grow quickly. They molt several times, wriggling face-first out of their old exoskeleton and then resting while their new one hardens. They have six pairs of simple eyes that detect shadows but not shapes, and sensitive little hairs all over their bodies.
Most caterpillars are easy prey for birds to feed to their nestlings, but birds avoid the conspicuous monarchs with their yellow, black and white bands. Monarch caterpillars eat only milkweed leaves, which contain a mild toxin that makes them — and the butterflies they will become — taste bitter, and can even make birds vomit.
After two weeks or so, monarch caterpillars attach themselves to a twig or leaf and shed their skin once more. This time, the new skin underneath hardens into a blue-green capsule called a chrysalis. It takes about two weeks before the caterpillar’s cells reorganize into an adult butterfly. Finally it emerges, plumps and dries its wings, and flutters off to feed by unrolling its long tongue to sip nectar from many different flowers.
Unlike the generation that overwinters in California or Mexico, adult monarchs on migration live less than two months. It takes at least four generations of monarchs to make the complete round-trip between their southern wintering areas and patches of milkweeds as far north as Canada.
As autumn approaches, cooler temperatures and shorter days trigger changes, preparing monarchs to make their long journeys to the south and west. They rely on cryptochromes — proteins in their antennae — to sense the Earth’s magnetic field and the violet-blue range of sunlight to guide them. Recently, new tracking methods indicate that monarchs on the western side of the Rockies emigrate to both California and Mexico, some of them via travel corridors through Arizona.
This is where we in Flagstaff enter the picture.
Monarchs lay their eggs only on milkweeds and cannot survive without them. Nectar-rich flowers are also essential to sustain monarchs as each flies hundreds or thousands of miles. Flagstaff’s native milkweeds are beautiful and three of them — spider, butterfly, and showy — are available locally as seeds or plants. Spider and butterfly milkweeds thrive where they are protected from wind and receive full sun for part of the day, while showy milkweed does best in more shady areas. Including milkweeds as well as nectar-rich native flowers in our gardens helps sustain monarchs on their amazing journeys across America.