Discovering the Superior Pollinator Support of Native Plants

In a groundbreaking investigation conducted by researchers at Oregon State University, native plants have been shown to provide significantly broader benefits to bees compared to their cultivated counterparts, known as cultivars. This study, centered at the university's Oak Creek Center for Urban Horticulture in Corvallis, Oregon, spanned four years from 2020 to 2023 and meticulously compared wild native species with 11 derived cultivars. The findings reveal that pollinators, particularly bees, interact more favorably with native plants, supporting greater diversity and functional richness in bee communities.

The research highlights how breeding for ornamental traits—like vibrant colors, compact growth, or extended bloom times—can unintentionally alter critical floral characteristics such as nectar volume, sugar concentration, and pollen nutrition. These changes often result in cultivars attracting fewer bee species or supporting less varied bee populations, underscoring the ecological advantages of sticking with straight species natives in gardens and landscapes.

The Critical Role of Bees in Ecosystems and Agriculture

Bees, as key pollinators, are indispensable for the reproduction of approximately 80 percent of flowering plants worldwide, including a substantial portion of our food crops. In the United States alone, pollination services contribute an estimated $15 billion to $20 billion annually to the agricultural economy, enhancing crop yields and quality for fruits, vegetables, nuts, and seeds. Native bees, which number over 4,000 species in North America, outperform managed honeybees in many contexts due to their efficiency and specialization on local flora.

However, pollinator populations face severe threats. Recent reports indicate that more than 52 percent of native U.S. bee species with sufficient data are declining, with over 22 percent at elevated risk of extinction. Factors like habitat loss, pesticides, climate change, and disease have led to staggering losses—up to 40 percent of commercial honeybee colonies in recent years. This decline not only jeopardizes biodiversity but also food security, as pollinators underpin one-third of the food we consume daily.

Defining Native Plants Versus Cultivars: A Key Distinction

Native plants are species that have evolved and coexisted with local wildlife in a specific region for thousands of years, such as the Pacific Northwest's Clarkia amoena (farewell-to-spring) or Symphyotrichum subspicatum (Douglas aster). They offer precisely tuned resources—nectar, pollen, and nesting sites—that match the needs of regional bees, including specialists with long tongues or narrow dietary preferences.

Cultivars, short for cultivated varieties, are selectively bred or hybridized versions of these natives, often labeled as 'nativars.' Bred primarily for garden appeal, they might feature double flowers, variegated leaves, or sterile pollen to prevent seeding. While aesthetically pleasing, these modifications can disrupt their pollinator appeal. The OSU study demonstrated this through direct comparisons, showing how even subtle breeding shifts impact bee visitation and community structure.

Methodology Behind the OSU Breakthrough

The Oregon State University team, led by postdoctoral scholar Jen Hayes from the Garden Ecology Lab, employed a rigorous common garden experiment. They planted replicates of five Pacific Northwest native plants alongside 11 cultivars derived from them, monitoring interactions over multiple growing seasons. Observations included pollinator visitation rates, species richness, and functional traits like bee body size, tongue length, and diet breadth.

Additionally, researchers quantified floral traits step-by-step: measuring nectar volume per flower using microcapillary tubes, assessing sugar content via refractometers, analyzing pollen protein and lipid levels in labs, and recording morphological features like corolla depth and inflorescence density. This multi-faceted approach provided comprehensive data, published in two parts in the journal Environmental Entomology, revealing causal links between plant modifications and pollinator responses. For full details, explore the OSU Extension summary.

Key Findings: Natives Outperform Cultivars Across Metrics

In the first phase, pollinators preferred native plants in 37 percent of comparisons, versus just 8 percent for cultivars, with no preference in over half the cases. Native plants consistently hosted higher total pollinator and bee richness. For instance, wild Clarkia amoena drew more visits from diverse bees due to its prolonged, abundant blooms.

The second phase uncovered trait shifts: nine of 11 cultivars exhibited reduced nectar, lower sugar, or altered pollen nutrition compared to natives. Bee communities on these cultivars were distinctly different, often lacking specialist species. Only a white-flowered Eschscholzia californica (California poppy) cultivar matched its native counterpart, while minimally selected Douglas aster varieties retained strong specialist support.

• Natives supported 20-30 percent more bee species on average.
• Cultivars showed narrower functional diversity, impacting ecosystem resilience.
• Ornamental breeding inadvertently reduced rewards by 10-50 percent in key traits.

Specific Plant Examples from the Study

The study spotlighted several pairs:

• Clarkia amoena (farewell-to-spring): Native bloomed longer, attracting five pollinator groups more frequently than its compact cultivar.
• Achillea millefolium (yarrow): Cultivars drew more honeybees but fewer native solitary bees.
• Symphyotrichum subspicatum (Douglas aster): Wild type supported unique specialists; seed-selected cultivars performed nearly as well.
• Eschscholzia californica (California poppy): Most cultivars underperformed except one color variant.

These examples illustrate that the degree of breeding modification correlates with pollinator support—minimal changes preserve value, heavy hybridization diminishes it.

Implications for Home Gardeners and Landscapers

For everyday gardeners aiming to bolster local bees, the message is clear: prioritize straight native species. They provide reliable, broad-spectrum support without the risks of reduced rewards in cultivars. Start by assessing your ecoregion—Pacific Northwest gardeners might plant goldenrod, milkweed, or lupine alongside OSU-recommended picks like Camas (Camassia quamash) or self-heal (Prunella vulgaris).

OSU's earlier research identifies top natives: vine maple for early spring, tall Oregon grape for berries and bees, and pearleverlasting for late-season nectar. Transition gradually: replace lawn with pollinator meadows, avoid neonicotinoid pesticides, and provide bare ground for ground-nesting bees (70 percent of native species). Check the OSU native plant picks list for regionally tailored options.

Agricultural and Breeding Perspectives

Farmers benefit too—native hedgerows boost wild bee populations, improving crop pollination efficiency by up to 50 percent in studies. Breeders can use these insights to develop 'pollinator-plus' cultivars, selecting for both beauty and bee-friendly traits like deeper corollas or higher nectar yields.

Stakeholders from conservation groups to nurseries emphasize balanced approaches: cultivars offer disease resistance and urban adaptability, but natives ensure resilience. Multi-perspective views, including from the Xerces Society, advocate integrating both while prioritizing wild types in critical habitats.

OSU's Leadership in Pollinator Research

Oregon State University's Garden Ecology Lab, under Gail Langellotto, pioneers urban pollinator studies, bridging academia and practice. This work builds on prior efforts like screening 23 Willamette Valley wildflowers, yielding top-10 lists still guiding gardeners today. As higher education drives solutions, OSU exemplifies how university research translates to actionable conservation.

Photo by Hiroko Nishimura on Unsplash

Actionable Steps and Future Outlook

To act now:

1. Source natives from reputable nurseries or seed swaps—verify non-hybrid status.
2. Plant in clusters for continuous bloom from spring to fall.
3. Monitor with apps like iNaturalist to track local bee diversity.
4. Advocate for native plant policies in communities.

Looking ahead, ongoing research promises pollinator-smart breeding and policy shifts amid climate pressures. With 2026 projections showing intensified bee declines, university-led innovations like OSU's offer hope for sustainable landscapes.