Keystone Plants by Ecoregion

ME, NH, VT, MA, RI, CT, NY, NJ

The Northeast's dense deciduous and mixed forests support some of the highest caterpillar diversity in North America. Oaks, cherries, and willows anchor the food web; goldenrod and asters sustain the late-season pollinator community.

PA, MD, DE, VA, WV, DC

The Mid-Atlantic sits at a biodiversity crossroads — northern forest species overlap with southern Coastal Plain communities across the Appalachians, Piedmont, and tidal shores. Native oaks support more caterpillar species here than anywhere else on the continent.

NC, SC, GA, FL, AL, MS, TN, KY

The Southeast's longleaf pine savannas, Appalachian coves, and Coastal Plain wetlands harbor more plant species than almost anywhere else in North America. Native oaks, cherries, and willows provide the same keystone function here as in the North — but a richer understory layer adds milkweed, pawpaw, and spicebush to the food web.

OH, IN, MI, WI, MN, IA, MO

The Midwest transitions from the eastern deciduous forest to tallgrass prairie — the most biodiverse grassland ecosystem that ever existed in North America. Keystone oaks and willows anchor the forest edges; native sunflowers, goldenrod, and big bluestem anchor the prairie remnants.

ND, SD, NE, KS, OK, TX (western), MT (eastern)

The Great Plains once supported the largest grassland ecosystem on Earth. Today it's among the most endangered. Keystone perennials — native sunflowers, goldenrod, gumweed, and prairie clover — support up to 89 specialist bee species each and are the foundation of grassland food webs.

MT, WY, CO, UT, ID, NM (northern)

The Rocky Mountain ecoregion spans dramatically different elevations — from dry sagebrush valleys to subalpine meadows and spruce-fir forests. Native willows dominate riparian corridors; aspen groves support the highest caterpillar diversity at mid-elevations.

WA, OR

The Pacific Northwest's maritime climate supports some of the most productive temperate rainforests on Earth. Native willows top the keystone rankings here; conifers (Douglas fir, western hemlock, Sitka spruce) support hundreds of caterpillar species in old-growth and second-growth forests.

CA

California's Mediterranean climate is unique in North America — long dry summers, mild wet winters, and exceptional plant biodiversity. Native willows top the caterpillar rankings; coast live oak and valley oak support 270+ wildlife species. Ceanothus, found almost nowhere else, supports 120 caterpillar species.

AZ, NM, NV, UT (southern), TX (western)

The desert Southwest hosts a distinct and specialized native plant community adapted to heat, drought, and intense solar radiation. Native sunflowers support the most specialist bees of any plant genus in this ecoregion; desert willows and mesquite anchor riparian and wash habitats.