Cultivar Landscape Design
As you start shopping for plants this spring, please emphasize regional native plants that support your local ecosystem. That sounds easy, doesn’t it? Well, it’s actually a bit more complicated. Sometimes the only native plants you can find are native cultivars, not open-pollinated, “straight species” natives. These native cultivars are often referred to as “nativars.”
For those of you who are newer to gardening, here is an example. The straight species of Purple Coneflower is Echinacea purpurea. Echinacea purpurea ‘Magnus’ is a cultivar, a plant that has been selected by man for certain traits and propagated to keep those traits.
Why does this distinction matter? For one thing genetic diversity is the foundation for biodiversity, which is the foundation for healthy ecosystems. Open-pollinated, straight species natives provide this genetic diversity; native cultivars do not. Finding locally grown straight species natives, is another key to supporting local ecosystems.
When you visit large wholesale growers, retail nurseries, or big box stores, the selection of native plants may be quite limited, and often a cultivar may be your only option. This is troubling, since it seems like the same cultivars of the same plants are offered absolutely everywhere. So much for genetic diversity!
Besides diminishing the genetic pool, there is another concern: do native cultivars provide the same ecological function in nature? We can figure some of this out through logic. For example, a sterile cultivar that does not produce seeds, will not feed seed-eating birds. It gets trickier when we start to factor in pollinators. We can often see which plants attract more insects, but that is the tip of the ecological iceberg.
There is exciting new research being conducted by Annie White, a PhD student in Ecological Landscape Design at the University of Vermont. Under the guidance of Dr. Leonard Perry, White is comparing what she calls “true open-pollinated native wildflowers” to native cultivars, in terms of their ability to attract and provide nectar and pollen resources to pollinators.
It appears that Annie White may be the first person to ever research this topic. Very timely research it is, with native bees, honey bees, and other pollinators facing serious challenges. White started her data collection in 2013, utilizing two research sites she established in Vermont. She has been studying 14 flowering perennial plants that are native to the Northeast, comparing each to a native cultivar. In the case of Echinacea purpurea, three cultivars were studied.
White observed pollinating insects visiting these plants. She recorded visits by native bees, honey bees, wasps, beetles and butterflies. White is most interested in bees, of which there are 275 species in Vermont.
Here is the list plants which Annie White is currently researching:
Achillea millefolium Common Yarrow Achillea millefolium ‘Stawberry Seduction’ Strawberry Seduction Yarrow Agastache foeniculum Blue Giant Hyssop Agastache foeniculum ‘Golden Jubilee’ Golden Jubilee Hyssop Aquilegia canadensis Wild Columbine Aquilegia canadensis ‘Corbett’ Wild Columbine Asclepias tuberosa Butterfly Weed Asclepias tuberosa ‘Hello Yellow’ Butterfly Weed Aster novae-angliae New England Aster Aster novae-angliae ‘Alma Poetschke’ New England Aster Baptisia australis Wild Indigo/Blue False Indigo Baptisia ‘Twilite’ Prairie Blues False Indigo Echinacea purpurea Purple Coneflower Echinacea purpurea ‘White Swan’ Coneflower Echinacea ‘Sunrise Big Sky’ Coneflower Echinacea purpurea ‘Pink Double Delight’ Pink Double Coneflower Helenium autumnale Common Sneezeweed Helenium autumnale ‘Moerheim Beauty’ Sneezeweed Lobelia cardinalis Cardinal Flower Lobelia cardinalis ‘Fried Green Tomatoes’ Cardinal Flower Monarda fistulosa Wild Bergamot/ Bee Balm Monarda fistulosa ‘Claire Grace’ Wild Bergamot/ Bee Balm Penstemon digitalis Beardtongue Penstemon digitalis ‘Husker Red’ Beardtongue Rudbeckia fulgida Black-eyed Susan Rudbeckia fulgida ‘Goldsturm’ Black-eyed Susan Tradescantia ohiensis Spiderwort Tradescania ‘Red Grape’ Spiderwort Veronicastrum virginicum Culver’s Root Veronicastrum virginicum ‘Lavender Towers’ Culver’s Root
To date, the research results are species-specific, with some plant pairs showing dramatic differences in each plant’s ability to attract pollinators. Echinacea purpurea ‘Pink Double’ did poorly compared to the straight species, while Echinacea purpurea ‘White Swan’ did rather well. For complete results on all the plants, please watch the accompanying video or listen to the podcast.