Growing your results…
In 2021, the National Wildlife Federation launched a formal keystone plant framework based on years of research by entomologist Dr. Doug Tallamy at the University of Delaware. The program identified the native plant genera with the highest ecological impact in each major North American ecoregion — and made that data publicly accessible through tools, regional plant lists, and a searchable native plant finder.
It's one of the most practically useful conservation resources available to home gardeners. But navigating its components — the research base, the ecoregion structure, the different tools, and how they connect — takes some explanation.
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The NWF initiative is built on two bodies of research.
Dr. Doug Tallamy's lepidopteran host plant data, developed through the University of Delaware, quantifies how many butterfly and moth caterpillar species each native plant genus supports. Published in Nature Communications in 2020, the research analyzed 83 U.S. counties and found that a small number of plant genera — approximately 14% — support 90% of butterfly and moth species in any given region.
These are the keystones. The remaining 86% of native plant genera are ecologically valuable, but they're not the load-bearing structures of the food web. The keystones are.
Jarrod Fowler's native bee pollen specialist research identified which native plant genera are required by pollen specialist bees — the 15–60% of North American native bee species that can only eat pollen from specific plant families or genera. For these bees, the right host plant isn't a preference; it's a survival requirement.
Together, these two datasets define what a "keystone plant" is in the NWF framework: a plant that serves as both a Lepidoptera host plant and a pollen specialist bee host, at outsized levels relative to other native plants in the region.
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The NWF organizes its keystone plant data by EPA Level I Ecoregions — broad geographic zones defined by shared ecological characteristics: climate, soils, vegetation, and wildlife. There are 12 Level I ecoregions in North America, ranging from Eastern Temperate Forests to the North American Deserts.
This matters because native plant ranges often extend across multiple ecoregions, but the wildlife relationships — the specialist insects, the caterpillar communities — are more locally specific. A plant native to the Eastern Temperate Forests is not automatically the right choice for someone in the Northwestern Forested Mountains ecoregion, even if both regions technically overlap the plant's distribution.
The 12 NWF ecoregion plant lists are:
Each list identifies the top keystone plant genera for that ecoregion, the number of Lepidoptera caterpillar species each supports, and the number of specialist bee species. The lists are downloadable as PDFs from the NWF website.
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The Eastern Temperate Forests ecoregion covers most of the eastern US — from Maine to Georgia, west to the edge of the Great Plains. It includes some of the most heavily populated and most ecologically degraded landscapes in North America.
The NWF's top keystone plant genera for this region, with caterpillar and specialist bee counts:
The pattern is consistent across ecoregions: trees (especially oaks, cherries, and willows) dominate for caterpillar support, while perennial wildflowers (goldenrod, asters, sunflowers) dominate for specialist bee support.
A landscape that includes at least one keystone tree, one keystone shrub, and one keystone perennial in each bloom window covers the essential bases.
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Native Plant Finder (nwf.org/nativeplantfinder) — Enter a zip code to get a ranked list of native plants for that location, sorted by the number of Lepidoptera caterpillar species each supports. Built in partnership with the U.S. Forest Service. Covers ~4,000 plant genera supporting over 11,000 Lepidoptera.
Keystone Plants by Ecoregion (nwf.org/keystoneplants) — Downloadable PDF lists for each ecoregion, including specific species recommendations and wildlife support data. More detailed than the Plant Finder.
Garden for Wildlife Certification — The NWF's certification program for home habitats. Certifying your yard requires native plants, water, shelter, and places to raise young. The program has certified over one million habitats since its founding.
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The NWF framework has inspired several complementary tools that extend or improve on its approach:
Homegrown National Park Keystone Tool (homegrownnationalpark.org/keystone-plants) — Uses EPA Level II ecoregions (more precise than Level I) for plant recommendations. Founded by Doug Tallamy himself. Useful for gardeners near ecoregion boundaries or in ecologically diverse states.
KeystonePlants.com Native Plant Finder (keystoneplants.com/search) — Our directory integrates the same underlying research with added filters for growing conditions, ecosystem type, nursery availability by state, and specific pollinator groups. Find keystone plants for your zip code plus local sources.
Xerces Society Pollinator Plant Lists (xerces.org) — Regional lists focused on pollinator support, particularly native bees. Complements the NWF framework with additional specialist bee data.
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The NWF initiative focuses on plants that support Lepidoptera and specialist bees. It doesn't explicitly cover:
Wetland keystone plants — species like cattail, bulrush, and sedges that perform critical water filtration and wetland habitat functions. See our wetland plants guide for this.
Invasive species avoidance — knowing which plants not to plant is as important as knowing which to choose. The NWF lists don't address invasives directly. See our native vs. invasive guide.
Nursery sourcing — the NWF identifies what to plant but doesn't help you find where to buy it locally. Our state nursery directory fills that gap.
Local ecotype sourcing — even within the right species, plants grown from regionally appropriate seed perform better and support more local wildlife. Seek out nurseries that specify seed provenance.
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The NWF initiative's most important practical implication is this: you don't need a lot of plants to make a big difference — you need the right plants.
A single white oak (Quercus alba) in a suburban yard, allowed to grow to maturity, supports more wildlife than an acre of well-maintained ornamental landscaping with no keystone species. The 14% of plants that support 90% of the food web are knowable, obtainable, and plantable in almost any landscape.
That's what the initiative makes possible — translating decades of ecological research into a list you can bring to a nursery.
Use our Native Plant Finder to find your ecoregion's keystone species, filter to your site conditions, and locate a local source.