Best gardening practices to benefit Arizona’s struggling monarch butterfly population

Everybody loves a monarch butterfly. The brilliant orange and black beauties, looking like they might have been crafted in Tiffany’s stained-glass studio, are one of the most recognizable insects in the garden. 

Over the past few decades, however, butterfly lovers, both amateur and professional, have sounded an alarm about the demise of the species. Some studies have shown that the monarch population in California plummeted from about 4.5 million in the 1980s to mere tens of thousands by 2018 (although preliminary counts from 2021 show a heartening rebound in the numbers).

Here in Arizona, entomologist Richard Hofstetter says it can be tough to gauge the health of the monarch population, because the numbers vary from year to year. However, the professor of forest entomology at Northern Arizona University says, “We’ve done a good job of tracking them, and last year was a pretty good year.” 

Hofstetter, who’s also active with Arizona Milkweed for Monarchs, a nonprofit group that raises and distributes the milkweed plants that monarch caterpillars feed on, says the colorful species can be spotted nearly year-round, especially in the southern part of the state. In the autumn months, they’re migrating toward Mexico, while come spring, they’re heading back to cooler climes. Along the way, female monarchs are searching for milkweed, the only plant on which they lay their eggs and the only food their larvae eat. 

The odds are stacked against the caterpillars. In the wild, only about 10 percent of eggs make it to butterfly stage. Birds love to feast on a fat, juicy caterpillar, and any number of insects enjoy the pinhead-size eggs.

If you want to help, the experts say, rethink your yard. Ryan Trudell, vice president of landscape architecture at Creative Environments, a Tempe-based landscape design firm, offers advice for designing a garden to promote monarchs and other pollinators. Butterflies are attracted to color, so be sure to include plenty of flowering annuals and perennials in bright hues.

Milkweed is a must, and Trudell says desert milkweed (Asclepias subulata) is a good choice. “It’s a reedy, grassy-looking plant with a nice vertical form,” he says. “I like to mass them in a nice drift.”

Once a butterfly has emerged, it needs nectar to thrive, so Trudell suggests a variety of flowering plants, from low-growing lantana and verbena to taller specimens such as daisies and red bird of paradise, to bushy plants such as Baja fairy duster (Calliandra californica) or wooly butterfly bush (Buddleja marrubiifolia). “Diversity is the key,” he says.

As much as we all hate weeds and pests, Hofstetter says working with nature is the best way to go. “Not using herbicides and pesticides can promote high biodiversity,” he says. Even so-called “natural” products will hurt butterflies, so if you value them—and other pollinators such as bees, birds, moths and bats—learn to put up with less-desirable species. The beautiful monarch is worth it.

More than Monarchs

There are literally hundreds of butterfly species that call Arizona home. See if you can spot any of these in your own garden.