Monarch Waystation Plants: Milkweed and Nectar Sources

title: "Monarch Waystation Plants: Milkweed and Nectar Sources"

The monarch butterfly (Danaus plexippus) was listed as threatened under the Endangered Species Act in December 2024, following a decades-long population decline that the US Fish & Wildlife Service documented as a greater than 85% decrease in the overwintering eastern population since the mid-1990s. The causes are habitat loss — specifically the loss of native milkweed throughout the breeding range — combined with loss of nectar plants along migration corridors and degradation of the overwintering sites in central Mexico and coastal California.

A "monarch waystation" is a habitat patch, however small, that provides the two things monarchs require: milkweed for breeding and larval development, and nectar plants for adults fueling their migration. The Monarch Watch Waystation program has registered over 40,000 sites as of 2024, and a waystation can be as small as a 100-square-foot backyard planting.

The milkweed imperative

Milkweed loss is the primary driver of monarch decline. Per a 2012 study in Insect Conservation and Diversity by Pleasants and Oberhauser, milkweed abundance in the Midwest agricultural landscape declined approximately 58% between 1999 and 2010, primarily due to the adoption of herbicide-tolerant corn and soybean crops that eliminated field-edge and in-field milkweed. That loss correlates directly with the monarch population decline during the same period.

The good news is that garden and restored habitat milkweed genuinely matters. Per Monarch Watch research, milkweed planted in residential areas, roadsides, and restored habitats contributes measurably to monarch reproductive success. The scale of what would be needed to reverse the trend is large — millions of acres — but individual gardens collectively add up, particularly along migration corridors.