Growing Native Plants is for the Birds … and the Bees!
Two research studies published in 2018 demonstrate the importance of growing native plants to sustaining biological diversity, whether in our gardens, along roads and highways, in public and commercial plantings, or adjacent to crops.
Backyards Need 70 Percent Native Plant Species
The first study, ground-breaking work by Doug Tallamy and other scientists at the University of Delaware and the Smithsonian Institution, found that non-native plants in backyard gardens endanger insectivorous birds (which include over one third of native bird species in the U.S.). Most plant-eating insects can eat only species with which they have coevolved; non-native plants often are toxic to them. Fewer insects mean reduced survival numbers for most bird species, which feed insects to their young. (See University of Delaware article.)
“The UD and Smithsonian research found the key threshold is 70 percent. If the yard has more than 70 percent native plants biomass, chickadees have a chance to reproduce and sustain their local population. As soon as the number of native plants drops under 70 percent, that probability of sustaining the species plummets to zero. To promote sustainable food webs and support wildlife, urban planners and private landowners must prioritize native plant species.” (1)
Which Native Species Best Support Beneficial Insects?
The second study was by UC Davis researchers who tested California native plant species (and one non-native) to determine which species best support beneficial insects. The goal was to “identify California native plants … suitable for the coordinated management of pollinators (wild bees and honeybees), insect herbivores and arthropod natural enemies.” (2)
Planting non-crop flowering plants adjacent to crops is a strategy to support an integrated ecosystem services, attracting pollinators while reducing the need for pesticides and herbicides. These plants also will enhance home-grown pollinator gardens.
Use Local Natives That Have Co-Evolved with Beneficials
The researchers identified 42 California native plants and one non-native that excelled in attracting and supporting beneficial insects. The result was a list of 42 California native plants and one naturalized non-native that are drought tolerant, bloom at different times throughout the season, are attractive both to pollinators and to insect predators, and are commercially available either as seed or plants. These plants can play similar roles in home gardens, whether the goal is to attract pollinators to your vegetable garden, create wildlife habitat, or restore the native ecosystem.
Plants that are locally native are specifically adapted to our climate and soils, and thus can thrive with less water and care than plants from other regions. Locally native plants have co-evolved with local beneficial insects, and provide the right food and habitat to sustain an integrated ecosystem. Redbud found that 32 of the 43 plants in the UC Davis study are native to Nevada County, Placer County, or both, but 11 are not.
Because of the clear advantages of local native plants, we created an adapted list that includes the 32 local natives from the study, plus recommendations for additional local native plants. We chose plants with characteristics similar to those that were not native here.
See Redbud’s list of our local natives supportive to birds, bees, and other beneficials.
___
(1) Narango, Desirée L., Tallamy, Douglas W., and Marra, Peter P. “Nonnative plants reduce population growth of an insectivorous bird.” Proceedings of the National Academy of Sciences of the United States of America (PNAS). Nov 6, 2018.
(2) Garvey, Kathy Keatley. “The Big 43: The California Native Plants, Plus One, Studies in UC Davis Research.” Bug Squad: Happenings in the Insect World. University of California, Agriculture and Natural Resources. https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=29036. Accessed Dec. 27, 2018.