Gardening: Plant milkweeds to help monarch butterflies

Yes, we have monarch butterflies in Spokane. We hear more about the plight of the monarchs in the Midwest than here, but they are here and need our help to survive and flourish.

The Turnbull Wildlife Refuge in Cheney and the Xerces Society teamed up June 23 for a workshop on the monarch’s lifecycle and what gardeners can do to help strengthen our small Eastern Washington population. The workshop was led by Candace Fallon, a senior conservation biologist with the Xerces Society. Based in Portland, the Xerces Society works to build and preserve habitat and raise awareness of the plight of many insect species.

According to Fallon, there are several reasons for the decline of monarch populations. Development and disturbance of habitat is reducing populations of native milkweed, the only plant that the monarch larvae feed on. Herbicides and insecticides sprayed in gardens and on open land are killing the milkweed as well as the monarch larvae. Mowing and spraying roadsides and overgrazing fields also contribute to the loss of milkweeds.

Scientists also say climate change is affecting the insects, their ability to travel to their wintering grounds and the stability of milkweed meadows.

Most of the western U.S. population of monarchs overwinters along the coast of Southern California, especially around Pismo Beach south of San Luis Obispo. This contrasts with the Midwestern monarchs that traditionally travel to southern Mexico. As the weather warms in the spring, the adult monarchs begin their trip north. They generally arrive at the Turnbull Refuge about now but because the weather has been colder than normal they have not shown up yet.

Once the females arrive, they will lay a few eggs on the underside of showy milkweed leaves. The caterpillar hatches and then goes through four instar stages before the fifth stage’s large, black, yellow and cream-colored caterpillar spins a green cocoon from a small branch.

While the caterpillars are in the instar stages, they can eat up to two to three milkweed leaves a day. The caterpillar will take about two weeks to transform into an adult monarch. Adults are orange with black stripes through their wings.

An adult monarch born early in the season will live two to five weeks, laying eggs before it dies. At the end of the season however, adults born just before migration don’t breed – allowing them to live eight to nine months, enough time to go south and then return in the spring.

If you want to encourage monarchs to come into your garden, you must plant milkweeds. They need full sun and prefer damper areas of the garden. Once established they can spread with underground runners.

While our native showy and narrow leaf milkweeds are the best choice, species from other parts of the country will work. Our native milkweeds are available as plants or seed from Northwest native plant nurseries or in some specialty nurseries in the spring.