- Barbara Murphy
Are Native Plants Always the Best?
The gardening world is buzzing with articles encouraging everyone to garden for pollinators. Creating spaces that support insects, pollinators, and birds allows everyone to be a conservationist. Together, our small spaces help replace the lost habitats of monarch butterflies, native bees, and hummingbirds. Sign me up! I, too, want to feel like my actions make a difference. This message is being heard. For example, in just three years, the National Pollinator Garden Network registered over one million pollinator gardens. Doug Tallamy's Homegrown National Park has also captured the imagination of many.
Blended into these conversations is strong encouragement to use native plants since some studies suggest that native bees prefer native plants (but not exclusively) for pollen and nectar gathering. This is easier said than done, especially if you are looking for herbaceous perennials. In the spring, most of us head to a local greenhouse or nursery to make our purchases. There, the array of plant choices is stunning and could include species, cultivars, and nativars. What isn't clear is whether these plant types are equally good for pollinators?
There are many definitions of "native plant" that often contradict each other. One that seems to cover the important points is “native plants are those that have evolved and adapted to a specific location and have remained genetically unaltered by humans.” This definition avoids some of the current confusion with plants being labeled, native to the United States, but aren't necessarily native to a particular state. Or, plants that are native to a particular state, but not to your region. This definition implies that plants have adapted to local soil, moisture, and weather conditions and may have specific relationships with some pollinators. Taking this idea to its most stringent level, plant choices would be limited to what occurs/occurred naturally in your region, or abit more broadly, in your state.
Native plants are not widely available. Instead, cultivated varieties of native plants, commonly called cultivars or nativars, are abundant. Nativars are plants that have been selected by humans and cross-bred or hybridized by plant breeders seeking desirable characteristics such as different flower color, petal number, disease resistance, or leaf color, that can be maintained through propagation. They are identified by having a name included in a single quotation for example, Echinacea 'White Swan'.
Nativars are plants that have been selected by humans and cross-bred or hybridized by plant breeders seeking desirable characteristics such as different flower color, petal number, disease resistance, or leaf color, that can be maintained through propagation.
If your goal is to garden for pollinators, how important is it to focus your gardening efforts solely on native plants? As with everything in life, the answer is complicated. To begin with, there is very little long-term data comparing pollinator benefits of native flowers to non-native flowers or cultivars. One small study often cited, conducted in Vermont compared pollinator visits to 14 native species and 12 native cultivars. The results were mixed. For seven of the twelve species tested, pollinators had a clear preference for the straight species. For four of the species, there was no difference between the cultivar and the straight species in terms of pollinator attraction. And in one case, pollinators actually preferred the cultivar to the straight species.
Also part of the native plant discussion is the point that some pollinators have evolved specific relationships with native plants. A good example of this is monarch butterflies. Yes, milkweed is required for egg-laying and larva development. However, in the limited experience we have had in the Pollinator Garden at Valentine Farm, monarchs also lay eggs on a cultivar, 'Ice Ballet'. Also, the adult butterfly doesn't feed on milkweed. They need nectar flowers, the more types the better.
And what about the generalists, the insects that collect pollen and nectar from a variety of flowers? Research indicates that flying insects of all types are experiencing population declines. To counteract this trend, planting flowers with different colors, bloom times, heights, and shapes could benefit insects in general in addition to specific pollinators.
Another consideration is how close to native is native enough? Is a plant that is native to Vermont close enough geographically to be considered native to Maine? Importantly, if this plant were planted in Maine, would it attract fewer pollinators than in its native state of Vermont?
Finally, none of us are gardening in a native environment. All of us live on altered ground - trees were removed, land was excavated, lawns installed. A place that once supported mature trees with moist, shady understory and soils now has a neighborhood of houses in full sun with lawn as the dominant crop. Climate change is altering everything in ways we can’t imagine or can plan for…warmer temperatures, shortened and lengthened seasons, more rain at times, drought spells, earlier flowering, later frosts…sigh.
So what is a gardener to do? There are no clear answers yet again, but here are some suggestions:
Cause no harm. Don't knowingly plant invasive species. Even this relatively simple statement is tricky as the invasive species list seems to expand daily.
Don't use pesticides. Just don't.
Ask questions. Is the plant you are considering purchasing grown without pesticides? The tag says "bee-friendly" which bees benefit? Only by demanding more, better information will the garden industry change its practices and plant offerings.
Include some native plants in your garden. The insects that are dependent on this class of plants need them to continue to survive. But…
Include a diversity of plants in your landscape. Diversity begets diversity and don't forget to include trees and shrubs. Often, it is the woody plants that provide food for caterpillars that feed our birds.
Finally, just garden both for food and flowers. Gardening opens a window into the background of life. Lingering in the garden allows us to notice the small things that buzz and hum, the timing of flowers, the way light filters through leaves, the ripening of a tomato. It is also a skill that is disappearing, so share your knowledge and enthusiasm with others.