What Are Keystone Plants? The Science Behind Nature's Most Powerful Native Species

If you've spent any time researching native plants, you've probably come across the term "keystone plants." But what does it actually mean — and why does it matter so much for the wildlife in your backyard? This guide explains everything, from the research that defined the concept to why choosing the right native plants is one of the most impactful things you can do for local biodiversity.

The Short Answer

A keystone plant is a native plant species (or genus) that supports a disproportionately large share of local wildlife — especially caterpillars and specialist bees — relative to how many plant species exist in a region.

Think of it like the keystone in a stone arch: pull it out, and the whole structure collapses. Keystone plants function the same way in local food webs. Remove them, and populations of insects, birds, and other wildlife begin to unravel — even if you've filled your yard with other plants.

Who Coined the Term? The Research Behind Keystone Plants

The concept of keystone plants was popularized by Dr. Douglas W. Tallamy, a professor and chair of Entomology and Wildlife Ecology at the University of Delaware. Tallamy is widely regarded as one of the most influential voices in the modern native plants movement and is the author of acclaimed books including Bringing Nature Home, Nature's Best Hope, and his 2025 title How Can I Help?: Saving Nature with Your Yard.

Tallamy's interest is rooted in a deceptively simple question: which plants actually support wildlife, and which ones are basically ecological dead weight?

To answer it, he and his research team — including Dr. Desiree Narango and Kimberley Shropshire — compiled and analyzed data on 12,072 native Lepidoptera species (butterflies and moths) and 2,079 native plant genera across the United States. Their findings, published in Nature Communications in 2020, revealed a striking pattern:

Just 14% of native plant species support 90% of caterpillar species. Only 5% of native plants account for 75% of all caterpillar food.

In practical terms: you could plant a yard full of native plants and still provide almost nothing for wildlife — if you pick the wrong natives. The ecological value of plants is not distributed evenly. A small group of "powerhouse" genera does the heavy lifting for the rest of the food web.

Why Caterpillars? The Food Web Connection

You might be wondering: why the focus on caterpillars? Aren't pollinators like bees and butterflies more important?

Caterpillars are, in Tallamy's words, "the most important link in the food chain." Here's why:

Caterpillars are the primary food source for birds raising young. Research shows that 96% of terrestrial bird species in North America feed insects — primarily caterpillars — to their nestlings. Seeds and berries simply can't provide the protein density that growing chicks require.

To put that in concrete terms: a single pair of Carolina chickadees needs between 6,000 and 9,000 caterpillars to successfully raise just one brood of nestlings. And caterpillars can only survive on the plants they've co-evolved with — mostly native species.

The math is stark. A native oak (Quercus species) can host over 500 species of caterpillars in the Mid-Atlantic, and up to 897 across the U.S. A non-native ginkgo tree, equally large and equally green, supports just 5. Landscaping with ornamental non-natives doesn't just fail to help — it actively starves the food web.

Caterpillars are also uniquely efficient energy converters. They transfer more energy from plants to other animals than any other type of plant-eating insect. When caterpillar populations collapse, the ripple effects are felt all the way up to birds, bats, and larger predators.

The Keystone Concept: It's About Ecology, Not Just Beauty

One of the most important things to understand about keystone plants is that being native isn't enough on its own. Not all native plants are equal.

As Tallamy himself has said: "You can have a landscape comprised of 100 percent native plants and still support little because you've chosen natives that don't make a lot of food."

This is what separates a keystone plant from just any native plant. A keystone species or genus has co-evolved with local insects so deeply that dozens, hundreds, or even thousands of species of Lepidoptera depend on it as a host plant. Many of those insects are specialists — they can only eat one genus or even one species of plant. Without that plant, they vanish entirely from an area.

The same principle applies to bees. Research by pollinator conservationist Jarrod Fowler found that 15–60% of North American native bee species are pollen specialists — they collect pollen from only a narrow range of native plant genera. This reinforces the urgency of identifying and planting the keystone genera that support the most specialists.

What Makes a Plant "Keystone"? The Key Criteria

A plant earns keystone status when it meets most or all of these conditions:

1. It's native to the specific ecoregion — not just to the country or state, but to the local ecosystem where it evolved.
2. It hosts a high number of Lepidoptera (caterpillar) species — typically dozens to hundreds.
3. It supports specialist bees — providing pollen that specialist bee species require.
4. It is ecologically irreplaceable — no non-native substitute performs the same function, even if it looks similar.
5. Its removal would destabilize the local food web — reducing caterpillar diversity, bird breeding success, and insect abundance.

Top Keystone Plant Genera in the U.S.

Keystone Trees & Shrubs

• Quercus (Oaks) — 897 Lepidoptera species hosted
• Prunus (Cherries, Plums) — 456 species
• Salix (Willows) — 456 species
• Betula (Birches) — 400+ species
• Acer (Maples) — 285+ species
• Pinus (Pines) — 200+ species
• Ulmus (Elms) — 200+ species

Keystone Herbaceous Plants

• Solidago (Goldenrods) — top caterpillar host and major late-season nectar source
• Symphyotrichum (Native Asters) — hosts 100+ Lepidoptera; critical fall food for monarchs
• Helianthus (Sunflowers) — host plant and pollen source for specialist bees
• Rudbeckia (Black-Eyed Susans) — strong pollinator and Lepidoptera support
• Coreopsis (Tickseeds) — important for specialist bees
• Asclepias (Milkweeds) — sole larval host for monarchs; also supports specialist bees

For detailed profiles of all 20 keystone genera — including caterpillar counts, regional species recommendations, and growing notes — see our Top 20 Keystone Plant Species for Wildlife guide.

Why "Native to Your Ecoregion" Matters More Than You Think

One of the most important nuances in keystone plant research is that keystone status is local, not universal. The same genus can have wildly different ecological value depending on where you live.

The National Wildlife Federation and Homegrown National Park have organized keystone plant data by EPA Level II Ecoregions — geographic areas with similar ecosystems, climate, and plant communities. A goldenrod that's a top keystone plant in the Eastern Temperate Forest ecoregion may be a different species than what's native to the Mediterranean California ecoregion, and the insects that rely on each are also different.

This is why planting "native plants" in a general sense isn't enough. A plant native to Virginia may have limited value if you're gardening in Washington. The right question isn't "Is this plant native to the U.S.?" but "Is this plant native to my specific ecoregion, and does it have high keystone value for the insects and birds that live here?"

The Bigger Picture: Why This Matters Now

Insect populations in North America are in serious decline. Flying insect abundance has dropped by an estimated 78% over the past 40 years in some regions. The cause isn't a single villain — it's a combination of habitat loss, pesticides, light pollution, and the widespread replacement of native plants with ornamentals that support almost no insects.

The landscapes we choose to create around our homes, businesses, schools, and public spaces are now the primary driver of whether local food webs persist. There simply isn't enough undisturbed natural land left to compensate for insect-hostile suburban and urban areas.

This is the premise behind Tallamy's Homegrown National Park initiative: if every landowner in the U.S. converted even half of their lawn to native plants — with an emphasis on keystones — it would create a connected web of habitat larger than all national parks combined.

Keystone plants are the starting point of that restoration.

How to Find the Right Keystone Plants for Your Location

Ready to plant? Here's how to find the most ecologically impactful native plants for your specific location:

1. Use the NWF Native Plant Finder — enter your zip code at nwf.org/nativeplantfinder to see which plants support the most Lepidoptera in your area.
2. Check the NWF Keystone Plants by Ecoregion page — downloadable PDF lists by EPA Level II ecoregion, organized by top trees, shrubs, and perennials.
3. Use the Homegrown National Park Keystone Tool — search by zip code to find keystone genera for your specific ecoregion, including container-friendly options.
4. Find a native plant nursery near you — not all nurseries carry true-native keystone plants. Our regional directories list nurseries that specialize in keystone and native species.

Summary: The Case for Keystone Plants in 5 Numbers

• 14% — the share of native plant species that support 90% of caterpillar species
• 5% — the share of native plants that account for 75% of all caterpillar food
• 96% — the share of terrestrial bird species that feed insects to their young
• 6,000–9,000 — caterpillars needed to raise one brood of baby chickadees
• 500+ — caterpillar species a single native oak can support

Frequently Asked Questions

Are keystone plants the same as native plants?

No — all keystone plants are native plants, but not all native plants are keystones. Keystone plants are a specific subset that support a disproportionately large share of local caterpillar and bee diversity.

Can I grow keystone plants in a container or small yard?

Yes. Many keystone herbaceous plants like goldenrods, asters, and coneflowers grow well in containers. Homegrown National Park's keystone tool specifically includes container-friendly options.

Do keystone plants require special care?

Generally not. Because they're native to your ecoregion, keystone plants are adapted to local rainfall, soils, and temperatures. Once established, most require less water and maintenance than traditional ornamentals.

What if I rent and can't change the landscape?

Container gardens with keystone herbaceous plants (goldenrods, native asters, milkweeds) can still make a meaningful difference. Even a few keystone plants on a balcony or patio adds to the larger habitat network.

Do keystone plants attract "pest" insects?

Yes — and that's the point. Caterpillars that feed on keystone plants are primarily eaten by birds before they cause significant leaf damage. Tallamy's research consistently shows that functional ecosystems with abundant caterpillars and birds are visually indistinguishable from conventional ornamental landscapes.

Ready to start planting? See our [Top 20 Keystone Plant Species for Wildlife](/resources/top-20-keystone-plants) guide for ranked profiles of the highest-impact genera, then [browse nurseries near you](/nurseries) that carry them.