Front Range Biodiversity: Keystone Native Plants for Ecological Garden Design
Did you know that just 14% of native plant species support 90% of the caterpillars that birds depend on to feed their young? These crucial plants are called keystone species.
Fresh from the Best Practices for Pollinators summit, I'm convinced that education about keystone plants is our most powerful tool for restoring biodiversity. Understanding these ecological MVPs transforms how we see our landscapes.
A single oak tree can host over 500 species of caterpillars. A native willow supports more than 450. These aren't just plants—they're entire ecosystems in themselves, and knowing the difference between a high-impact native and a low-value ornamental changes everything.
What Are Keystone Plants?
Keystone plants, a term popularized by renowned entomologist Dr. Douglas W. Tallamy, are native plant species that form the foundation of local food webs. Just as the keystone in an arch is essential to the structure's integrity, these plants are vital to the survival of numerous wildlife species.
According to research from the University of Delaware, a mere 14% of native plant genera support an astounding 90% of butterfly and moth species. Similarly, research by horticulturist Jarrod Fowler reveals that 40% of native plants feed 15% to 60% of North American native bee species that are pollen specialists.
In the simplest terms, keystone plants are the most productive plants that support the most species. Landscapes without these critical plants will have failing ecosystems, even if they contain many other types of plants.
Why Native Plants Matter
Native plants have co-evolved with local wildlife over millions of years, forming intricate relationships that non-native plants simply cannot replicate. Here's why they're irreplaceable:
1. Specialized Relationships
Many insects, particularly specialist pollinators, can only feed on specific native plants. For example:
Monarch butterflies rely exclusively on milkweed (Asclepias species) as host plants for their caterpillars
Spring beauty mining bees collect pollen only from spring beauty flowers (Claytonia)
Squash bees are specialized to pollinate plants in the Cucurbita genus (squash, pumpkins)
These specialized relationships mean that without the right native plants, these insects cannot survive, reproduce, or fulfill their role in the ecosystem.
2. The Biodiversity Cascade
The relationship between plants and insects affects the entire food web:
Native plants feed specialist insects
These insects feed birds, reptiles, amphibians, and mammals
These animals, in turn, become food for larger predators
When we replace native plants with non-native ornamentals, we disrupt this cascade at its source.
3. Plant Productivity
Native keystone plants are incredibly productive in supporting wildlife. For instance:
A single native oak tree can support over 500 species of caterpillars
Native willows can host more than 450 species
Native cherries can support over 400 species
By contrast, non-native ornamentals like Ginkgo biloba (native to China) may support only a handful of insect species in North America.
Why Asian Ornamentals Fall Short
Many popular landscaping plants originated in Asia and other distant regions. While they may be prized for their ornamental value, resistance to deer, or low maintenance requirements, they often fail to support local wildlife for several key reasons:
Evolutionary History: Our local insects haven't evolved with these plants and often can't recognize them as food sources
Chemical Defenses: Many non-native plants have unfamiliar chemical compounds that make them indigestible or toxic to native insects
Specialist Limitations: Specialist pollinators physically cannot utilize the pollen or nectar from plants they didn't evolve with
Timing Mismatches: Non-native plants may flower or produce leaves at times that don't align with the life cycles of local insects
Even popular "pollinator-friendly" non-natives like butterfly bush (Buddleja davidii) provide nectar for adult butterflies but cannot serve as host plants for their caterpillars – making them essentially "ecological traps" that look helpful but don't support complete life cycles.
Specialty Pollinators: The Hidden Workforce
While honeybees get much of the attention, they're actually non-native to North America. Our ecosystems evolved with thousands of native bee species, many of which are specialists:
Oligolectic bees: These bees collect pollen from only a limited range of plant genera or families
Monolectic bees: These highly specialized bees collect pollen from just one plant species
For example:
Squash bees (Peponapis pruinosa) visit only plants in the Cucurbita genus
Pickerelweed specialist bees (Dufourea novaeangliae) collect pollen only from pickerelweed
Evening primrose bees (Lasioglossum oenotherae) are dependent on evening primrose
Without their specific host plants, these specialized pollinators simply cannot survive.
Building Biodiversity: How to Support Keystone Species
Ready to make your landscape a biodiversity hotspot? Here's how:
Know Your Ecoregion: Different parts of North America have different keystone plants. The National Wildlife Federation's Native Plant Finder (nativeplantfinder.nwf.org) can help you identify keystone plants for your specific zip code.
Prioritize Top Performers: Focus on these keystone genera that support exceptional numbers of wildlife:
Oaks (Quercus)
Cherries/Plums (Prunus)
Willows (Salix)
Birches (Betula)
Poplars/Cottonwoods (Populus)
Maples (Acer)
Goldenrods (Solidago)
Asters (Symphyotrichum)
Sunflowers (Helianthus)
Plant in Layers: Include trees, shrubs, perennials, and groundcovers to create a complex habitat structure
Reduce Lawn Areas: Replace portions of traditional turfgrass with native plant communities
Leave the Leaves: Allow fallen leaves to remain as natural mulch and habitat for overwintering insects
Avoid Pesticides: These chemicals kill not only target pests but also beneficial insects that form the base of the food web
Small Actions, Big Impact
You don't need a large property to make a difference. Even a small balcony container garden with native plants can provide crucial resources for local wildlife. Every square foot converted from non-native ornamentals to native keystone species helps restore the ecological relationships that sustain biodiversity.
By incorporating keystone native plants into our landscapes, we're not just creating beautiful gardens – we're rebuilding the ecological foundations that support entire food webs. The hummingbirds, butterflies, bees, and songbirds that bring joy to our outdoor spaces depend on these plant relationships that have evolved over millions of years.
So the next time you're selecting plants for your landscape, remember that your choices have the power to collapse or support your local ecosystem. Choose native keystone plants, and watch your garden transform into a vibrant hub of biodiversity!
Larkspur Landscaping specializes in ecological garden design. We create beautiful landscapes that support local ecosystems through thoughtful use of keystone native plants. Contact us to transform your yard into a vibrant habitat for wildlife.
Want to learn more? Check out Dr. Douglas Tallamy's books "Bringing Nature Home" and "Nature's Best Hope," or visit the National Wildlife Federation's Native Plant Finder at nativeplantfinder.nwf.org to discover the best keystone plants for your specific region.
