Click for previous Image Image 1 of 2 Click for next Image
Asclepias tuberosa

Asclepias tuberosa

Natives vs. Native Cultivars

Published March 10, 2017

Which are most valued by pollinators?

By: Debbie Hamrick NewTerrain 

It’s an argument undertaken by thousands of horticulturists, ecologists, entomologists and others that seek to maximize pollinator health and habitat: Natives vs. native cultivars. Plant lists online and in books abound. Philosophical opinions on all sides of the topic plant poles for the discussion: Natives are best for native pollinator species -- going further, natives of the provenance are gold standard. But does that mean that selections of natives have no pollinator benefit? Cultivars of native plants are marketed as natives and have been bred for aesthetics, but do they offer high-quality habitat? Thankfully, the discussions are increasingly being informed by structured, scientific observation.

Annie White, newly minted PhD from the University of Vermont, conducted her research on the question of natives vs. native cultivars. She asked the question: Are cultivars ecologically equivalent to native species? She worked at two sites in northern Vermont in Franklin and Essex counties to document pollinator visits on hundreds of plants.

Rather than thinking in absolutes, she developed a spectrum of flower benefits based on how much breeding a selection has undergone. Unmodified natives, she says, are best for pollinators followed by minimally modified natives and moderately modified natives, two types of selections that she terms good for pollinators. However, highly modified natives (think semi-double or double flowers) have variable value to pollinators.

She also takes into consideration flower shapes and sizes and their value to pollinators. The U.S. sports thousands of native bees from small to large, some with short tongues and others with long ones. It’s no surprise then that not all bees find all flowers attractive for foraging. Likewise, pollinators and gardeners do not necessary value the same things in flowers: Gardeners want flowers that look good, meet their height and plant habit expectations, are hardy and produce an abundance of flowers, among other criteria. Pollinators seek plants that first, require a pollinator, then those flowers must have the right corolla length, flower color and flower abundance.

Annie’s top performing native perennials are: Symphyotrichum novae-angliae; Veronicastrum virginicum; Agastache foeniculum; Asclepias tuberosa; Helenium autumnale; and Eutrochium maculatum.

The main body of her research is being published and not yet available, so stay tuned. In the meantime, if you’d like to reach out, you can contact Annie at Nectar Landscape Design Studio at annie@nectarvt.com.