When it comes to the birds and bees, native plants are typically more valuable than their cultivars
by Nicole Rivard
We know you are reading Action Line because you care about animals and the environment, and we know that, like us, you are concerned about the sixth great extinction the world is facing.
The good news is you actually have the power to slow the rate of extinction by what you do in your own garden and backyard, and that’s empowering!
The best thing you can do for animals and the environment is plant flowering plants, shrubs and trees that are native to the area in which you live, according to Dr. Douglas Tallamy, author of Bringing Nature Home, and a professor at University of Delaware.
Native plants are the indigenous terrestrial and aquatic species that have evolved and occur naturally in a particular region, ecosystem and habitat. Species native to North America are generally recognized as those occurring on the continent prior to European settlement.
Tallamy lectures all over the country about how specialized relationships between animals and plants are the norm in nature rather than the exception. Of course native species will differ according to where you live in the United States. But overall his message is simple: Plants that evolved in concert with local animals provide for their needs better than plants that evolved elsewhere.
“He argues that almost all birds need to feed their young on insects. He talks about things like the importance of growing native plants that will attract native caterpillars, because birds need caterpillars to rear their young,” said Dr. Kimberly Stone, a bee researcher at the Connecticut Agricultural Experiment Station who, on Jan.1, 2017, published A Citizen’s Guide to Creating Pollinator Habitat in Connecticut.
“In his book he shares statistics on how many caterpillars a chickadee needs to eat in order to successfully raise a clutch of young. And he talks about which native plants attract the greatest diversity of caterpillars and presents that as a good thing, because of course gardeners for a long time have been wanting plants that don’t have caterpillars feeding on them. They saw that as a bad thing. His research is changing that whole mindset.”
Tallamy’s research has shown that alien ornamentals support 29 times less biodiversity than do native ornamentals. He points out that in the United States gardeners often plant Kousa dogwood, a species from China that supports no insect herbivores, instead of our native flowering dogwood (Cornus florida) that supports 117 species of moths and butterflies alone.
“In hundreds of thousands of acres we have planted golden raintree from China instead of one of our beautiful oaks and lost the chance to grow 532 species of caterpillars, all of them nutritious bird food,” Tallamy writes.
THE MOVEMENT TOWARDS NATIVE—AVOIDING THE PITFALLS
As a bee researcher, Stone is thrilled that Tallamy has developed a constituency over the last several years, and says that when you combine that with the fact that initiatives to address pollinator decline are widespread and growing in the United States—there truly is a movement towards cultivating habitats that foster pollinators.
However, while a growing demand for native plants and ecological landscaping sounds fantastic, there is more to the story. The demand has led to the selection and breeding of native cultivars by the nursery and landscape industry.
A cultivar is a human-bred variety of a native plant that has been selected, cross-bred, or hybridized for more “desirable” characteristics. In fact, cultivars are becoming more readily available for purchase at garden centers than true “straight” natives.
The problem is that some of the traits humans find attractive in cultivars when they try to create that jaw-dropping garden that is the envy of their neighbors—such as larger flowers, double flowers, shorter stems, or unique color—can actually make the plant less attractive to pollinators, according to research like that from PhD. candidate Annie White at the University of Vermont, and Penn State’s Pollinator Trial, a study that took place from 2012-2105.
“There are several different people who are doing research on this, but its research in progress, so there’s not really a simple story to tell,” Stoner said.
In some cases, the research is showing these forced characteristics may actually decrease the quantity, quality and accessibility of the nectar and pollen rewards. Research at the University of Vermont indicated that of the 13 plant pairs being evaluated, seven of the cultivars attracted significantly fewer bee pollinators than the straight species. There was no significant difference in pollinator visits in five of the pairs, and one cultivar attracted significantly more native bee pollinators than the straight species.
One clear trend was observed across all species; the more manipulated the cultivars became, the less attractive they became to pollinators. Although the research didn’t answer why some pollinators preferred the straight native species, researchers hypothesized the color differences and decreased nectar and pollen production in hybridized cultivars were leading factors.
In Penn State’s experiment, there were 14 direct comparisons and about 50 percent of the time the straight native species was better than the cultivar. For example, Monarda fistulosa, was substantially better than the cultivar, Monarda ‘Claire Grace’. On the other hand the cultivar Symphyotrichum ‘October Skies’ was substantially better than the straight native species Symphyotrichum oblongifolium.
Researchers concluded it was not possible to generalize that cultivars are always poorer than straight native species when it comes to being attractive to pollinators. Since research is just in the beginning stage of what needs to be more scientific evaluations of native species and all their cultivars, what’s a gardener to do?
Stoner advises gardeners who want to guarantee their plants will fit into their native ecosystem in a natural way and will attract pollinators should ask nurseries and garden centers for straight native species as opposed to cultivars.
“Asking for straight species will ensure you have a plants that fit into your local ecosystem that the animals in your area have evolved with. You may have to go to smaller more specialized nurseries in order to find the straight species,” Stoner said.
“I know, for example, that in Connecticut there are some really small nurseries focused on straight species of native plants that are native to Connecticut that don’t ship their plants to other places. I assume there are other nurseries like that around the country if you do some investigating.”
In terms of future research, Tallamy is currently looking at the straight species of woody plants and comparing them to cultivars that have been selected for interesting foliage, increased fruiting, disease resistance and plant habit.
He and other researchers are comparing the diversity and abundance of caterpillars in the food webs of straight species to their cultivars. Tallamy is forgiving when it comes to people who don’t realize their yards are wildlife preserves that represent the last chance we have for sustaining plants and animals that were once common throughout the United States.
“If this is news to you, it’s not your fault,” he writes. “We were taught from childhood that gardens are for beauty; they are a chance to express our artistic talents, to have fun with and relax in. And, whether we like it or not, the way we landscape our properties is taken by our neighbors as a statement of our wealth and social status. “
But no one has taught us that we have forced the plants and animals that evolved in North America to depend more and more on human-dominated landscapes for their continued existence. We have always thought that biodiversity was happy somewhere out there ‘in nature;’ in our local woodlot, or perhaps our state and national parks.
We have heard nothing about the rate at which species are disappearing from our neighborhoods, towns, counties and states. Even worse, we have never been taught how vital biodiversity is for our own well-being.”
Websites to visit for research on native plants and pollinators
NATIVE PLANT SOCIETIES: These organizations promote preservation, conservation, and knowledge about native plants. Most include a wide array of activities and information including field trips, wild wildflower walks, wildflower presentations, seed exchanges, native plant gardening, restoration information, photo galleries, botanical references, newsletters, plant lists, information about invasive plants and plant classes. www.fs.fed.us/wildflowers/links.shtml
THE XERCES SOCIETY: The Xerces Society is a non-profit organization that protects wildlife through the conservation of invertebrates and their habitat. Established in 1971, the Society is at the forefront of invertebrate protection worldwide, harnessing the knowledge of scientists and the enthusiasm of citizens to implement conservation programs. Their website is loaded with information including plant lists, identification guides, videos and more. The Xerces Society is a great resource hub for gardeners and landscapers seeking information on creating pollinator and beneficial insect-friendly gardens. www.xerces.org
WILD ONES: Wild Ones: Native Plants, Natural Landscapes promotes environmentally sound landscaping practices to preserve biodiversity through the preservation, restoration and establishment of native plant communities. They are a national non-profit organization with local chapters educating about the many benefits of growing native wildflowers in people’s yards. www.wildones.org
THE POLLINATOR PARTNERSHIP: The Pollinator Partnership’s mission is to promote the health of pollinators, critical to food and ecosystems, through conservation, education, and research. Their signature initiatives include the NAPCC (North American Pollinator Protection Campaign), National Pollinator Week, and Ecoregional Planting Guides. www.pollinator.org
UNIVERSITY OF VERMONT: PhD. candidate Annie White under advisor Dr. Leonard Perry is conducting research at the University of Vermont focused on evaluating flowering plant selection for pollinator habitat enhancement on open-pollinated natives vs. native cultivars. This project is funded in part through a Sustainable Agriculture Research & Education grant. More information: mysare.sare.org/ sare_project/ONE12-169/ and Annie’s website: pollinatorgardens.org