Hybridized and Native Cultivar Plants
I love native plants because of the value they provide to our pollinators. Natives provide more nectar and pollen than hybridized plants.
While hybrids are not detrimental to honeybees like neonicotinoids and other pesticides are, they are not beneficial either. Hybrids are bred in such a way that they produce very little nectar or pollen, so they would be useless in a garden intended to provide honeybees and pollinators in general with food. When you create a garden for bees and pollinators, it allows nature to claim the garden for its own.
Several studies suggest that wild bees prefer to forage—but not necessarily exclusively—on the nectar and pollen from native plants. Native plants are also typically well-adapted to local soil, climate, and other environmental conditions, making them more durable in the landscape. For these reasons, native plants are frequently recommended for pollinator habitat restoration and pollinator garden projects.
The growing demand for native plants in ecological landscaping, including pollinator habitat gardens, has led to the selection and breeding of native cultivars. A native cultivar or “nativar” is a cultivated variety of a native plant, that has been selected by humans (in nature or through repeated selections in a breeding program), cross-bred, and/or hybridized by botanists and plants breeders seeking desirable characteristics that can be maintained through propagation.
The flowers of native cultivars may vary from the native species in size, shape, abundance, color, and bloom time—all attributes known to influence pollinator visitation. In addition to floral traits, native cultivars are sometimes selected for disease resistance, and more predictable sizes and shapes than their wild relatives, making them more desirable landscape plants. But native cultivars can also be less hardy and may prefer different soil moisture and fertility than the species, and most serious of all, may not be as attractive and useful to pollinators.
Some of the traits that humans find attractive in native cultivars, such as a double flowers or an unusual color, may make the flower less attractive to pollinators, and furthermore, may decrease the quantity, quality, and accessibility of the nectar and pollen rewards.
The use of strongly selected cultivars is generally discouraged in ecological restoration projects, but native cultivars are widely available and widely used in the landscape industry. In fact, when gardeners visit their local garden centers, it’s often impossible to find true native species. Gardeners can find echinaceas (coneflowers) in every color, size, and shape possible, but will struggle to find a non-cultivated variety of Echinacea purpurea or Echinacea pallida.
With the National Pollinator Garden Network aiming to register one million pollinator gardens; the Pollinator Health Task Force aiming to enhance seven million acres of land for pollinators; and bee habitat on private farms remaining a priority of all conservation programs under the U.S. Farm Bill, it’s important that we understand if native cultivars are comparable substitutions for native species, and if they can perform the same ecological functions in pollinator habitat gardens.
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.
One clear trend was observed across all species; the more manipulated the cultivars became, the less attractive they became to pollinators. Cultivars such as Achillea millefolium ‘Strawberry Seduction’ and Symphyotrichum novae-angliae ‘Alma Poetschke’, which are the result of repeated selections in breeding programs, attracted significantly fewer pollinators in nearly all pollinator groups. The same held true for hybrid varieties from breeding programs such as Baptisia x varicolor ‘Twilite Prairieblues’ and Tradescantia ‘Red Grape,’ Echinacea ‘Sunrise’ Big Sky and Echinacea ‘Pink Double Delight.’ (I have these double-coneflowers throughout my landscapes to add color, and just because I love them. However, I can validate the research stated in White's article - the pollinators avoid these plants - I have a mass planting, and can attest to NO pollinators visiting these flowers.)
Although our research doesn’t answer why some pollinators strongly preferred the native species, we hypothesize that color differences and decreased nectar and pollen production in hybridized cultivars are the leading factors.
Results may vary in other regions and with other native species and native cultivars, but this research highlights that in some cases, pollinators (bees, in particular) exhibit strong floral preferences for native species. If evaluating native cultivars for use in a pollinator habitat garden, try to limit the use of cultivars to open-pollinated seed-grown “selections” or “sports” of the native species. Cultivars that differ significantly in color and morphology from the native species should be used cautiously and cultivars with hybrid origins should be avoided in the context of pollinator habitat restoration.
SHOPPING FOR PLANTS
As you start shopping for plants, 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. Before I was more educated on native plants versus nativars, I had bought a Pow Wow Wild Berry coneflower. I have this planted in with the native purple coneflower Echineacea Purpurea; and they had naturally spread throughout my planting. These are planted right in front of my porch, so I can sit on my porch and observe the pollinators that visit both types of plants. The pollinators (mostly honey bees, bumble bees and native bees) ONLY go to the native coneflower; if they happen to land on the Pow Wow coneflower, they move on very quickly, whereas they linger on the native coneflower. The Pow Wow coneflower is more vibrant - and has been selected for that characteristic; however, it does not serve the purpose that I need, but I am glad that I have a few sprinkled in my landscape - they had a little sizzle!
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.
When shopping for native plants at nurseries and garden centers, you will find that there are numerous cultivars available for native plants. For example if you are looking for purple coneflower (Echinacea purpurea), you may find dozens of cultivars such as Echinacea purpurea ‘PowWow Wild Berry’ and Echinacea purpurea ‘White Swan.’ Research has shown that some cultivars are not as attractive to pollinators as their wild ancestors, so choose cultivars carefully. As a general rule of thumb it is best to avoid hybrid cultivars, double-flowered cultivars, and cultivars that have a dramatic change in color or flower shape.
Ask your nursery if the plants you are buying have been treated with a systemic insecticide, such as neonicotinoids, within the last year. Scientists are currently studying and debating how dangerous these common insecticides are for bees, especially honeybees. But here is what we already know: systemic insecticides are absorbed into the plant’s tissues and can be transported to the nectar and pollen. High concentrations can be fatal to bees, butterflies, and other insect pollinators, and lower concentrations may affect their health and well-being. If your gardening efforts are motivated by a desire to support pollinator populations, it is best to avoid buying plants that have been treated with systemic insecticides, and of course, avoid applying insecticides in your landscape as well.
In addition, you will need to determine your plant hardiness zone in the region of the United States that you reside. For example, in 1996, when I moved to Des Moines, the hardiness zone was zone 4. In recent years, I suspect due to climate change, our hardiness zone was upgraded to zone 5. This opens up many more plants that can be used by a landscaper or gardener. Go to the USDA Plant Hardiness website to determine your zone.
If you are open to ordering plants online, and I have been very successful in doing so, I have two businesses to recommend: Prairie Nursery out of Westfield, Wisconsin and Prairie Moon Nursery out of Winona, Minnesota. They carry both live plants and seed.
I have talked a lady that walks our neighborhood that has a conservation effort on her farmstead. She recommended Allendan for native seed. I am hopeful to try their seed next year if our friend will plant Partridge Pea on his farm for our bees.
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