Support Native Wildlife by Planting Keystone Perennials

Keystone species are native plants that provide the maximum habitat benefit to local wildlife. Research shows that just 5% of a region's native plants host 70–75% of butterfly and moth species and supply essential pollen to specialist bees. Because these insects form the foundation of the local food web—feeding birds, bats, and other wildlife—keystone plants have an outsized ecological impact compared to other native species. Keystone designations are made at the ecoregion level because these relationships shift across the continent, meaning the right species varies by area.

Keystone plants will vary from region to region, but several genera of perennials are found throughout much of North America. These include asters, sunflowers, black-eyed Susans, and goldenrod, which are all part of the daisy family (Asteraceae).

Asters (Symphyotrichum spp. and Eurybia spp.) are estimated to be larval host plants for 112 species of Lepidoptera and provide pollen for many specialist bees. In the 1990s, following DNA testing, there was a reclassification within the Aster genus. Currently, the majority of native North American asters fall into two genera, Symphyotrichum and Eurybia. Their daisy-like flowers are composed of white-to-yellow disc floret centers surrounded by white, pink, blue, or purple ray florets, most blooming from late summer into the fall. They will have better growth and flowering when planted in full sun, but can tolerate some light shade.

Goldenrod (Solidago spp.) is the larval host plant for around 110 species of Lepidoptera and supports around 42 species of specialist bees. Erect, often woody stems are generally clump-forming. They grow well in full sun and will tolerate poor soil. Plume-like panicles or clusters of tiny, bright yellow flowers bloom from midsummer to fall. Unfortunately, goldenrod has been mistaken for ragweed, which blooms at the same time, and has earned an erroneous reputation for causing seasonal allergies. Goldenrod's pollen differs from ragweed's light, airborne pollen, and is heavy and not easily wind-borne.

Sunflowers (Helianthus spp.) are the larval host plant for around 73 species of Lepidoptera, and provide pollen for at least 50 species of specialist bees. There is a total of 56 annual and perennial Helianthus species native to North America, of which 38 are perennial. Perennial sunflowers have smaller flower heads than their annual relatives. Their daisy-like flowers bloom late summer into the fall and have bright yellow ray florets surrounding a central cone composed of yellow or brown disc florets. The perennial species are typically erect and clump-forming. They will bloom best in full sun but can tolerate partial shade.

Black-eyed Susans (Rudbeckia spp.) are estimated to be the larval host plant for around 31 species of Lepidoptera and a pollen source for 29 specialist bee species. There are 31 species of Rudbeckia native to North America, and they may be perennial, biennial, or annual, depending on the species. They will grow in full sun to partial shade and are typically tolerant of poor soil conditions. A long summer bloomer, most species have a black, brown, or green raised central cone of disc flowers surrounded by yellow or orange ray flowers. Deadheading will encourage more blooms.

The plants described above are just an example of some of North America's keystone perennials. If your goal is to support pollinators and the local food web, plant choice matters. Make wise plant choices and support the most insects with the fewest amount of plants by adding a keystone perennial to your garden.