Make your garden support your local ecosystem
“It is tempting to garden only for beauty, without regard to the many ecological roles our landscapes must perform. All too often, such narrow gardening goals result in a landscape so low in ecological function that it drains the vitality from the surrounding ecosystem.”
— Douglas Tallamy, “Nature’s Best Hope,” 2019
During February, I’ll be writing about Tallamy’s New York Times bestseller, in which he asks landowners to apply David Attenborough’s message about increasing biodiversity in our own yards and gardens. An ecologist and entomologist, Tallamy tells us we cannot continue to separate our private landscapes from the natural world. He writes, “In short, we no longer have the right to ignore the stewardship responsibilities attached to land ownership.”
Tallamy agrees with Attenborough that the natural world can replenish itself if given the chance. It will require people to adopt conservation as a “culturally embraced imperative” and to collectively practice landscaping that restores ecological balance rather than further degrading local ecosystems. In particular, rather than choosing landscape plants only for their ornamental value, we could choose plants that participate in the ecosystem.
Most people still maintain landscapes that are 90% lawn, with only 10% of the tree biomass that originally stood on the site. Eighty percent of the trees, shrubs and herbaceous plants in our yards are non-native species that evolved in Europe, Asia and South America. These plants do not support native wildlife, so they create a landscape that is, as Tallamy puts it, “biologically depauperate.”
To turn this around, he recommends converting at least half of the area in our yards covered in turf grass into native plantings. Looking around my front yard, I’m pleased that we have replaced 80% of the lawn with garden beds and borders; about 20% of the yard is a grass pathway that winds around the beds. However, when I inventoried the 18 different species of trees and shrubs in my front yard, I realized that only six are North American natives and only three are Oregon natives: a white oak tree (Quercus garryana), two mock orange bushes (Philadelphus lewisii), and a kinnikinnick (Arctostaphylos uva-ursi).
Of about 30 kinds of herbaceous perennials in my front garden, eight are North American natives and four are native to our western region: goldenrod (Solidago canadensis), western joe-pye weed (Ageratina occidentalis), tickseed (coreopsis lanceolata) and showy milkweed (Asclepias speciosa).
I love my pollinator garden, but most of the plants in it are native to Mediterranean regions, central and eastern Europe and southwest Asia. Although I see tons of bees in my garden, the majority of them are European honey bees, rather than native species that would turn my front yard into a site that supports local ecosystems.
It’s clear that I have more work to do. Tallamy advises us to become familiar with our surrounding eco-regions and to incorporate some of the native plant communities into our home, business and school landscapes. My neighborhood in east Medford was built within a native oak savannah and grassland eco-region. My house is situated between the coniferous forests at the top of Roxy Ann Peak to the east and the riparian eco-region bordering Bear Creek to the west.
One of Tallamy’s graduate students at the University of Delaware built a database of native plants by local eco-regions, available online at www.nwf.org/NativePlantFinder/.
When I type in my ZIP code, the program provides a list of native trees, shrubs, flowers and grasses in my area, which helps take the guesswork out of identifying which native plants would grow well in my yard.
What is particularly fascinating about the Native Plant Finder is that it sorts native plants by the number of native butterflies and moths that use a particular plant as hosts. Tallamy points out that focusing on growing the number of caterpillars in our yard is an effective way to increase biodiversity. According to the NPF, if I added a native species of strawberry to my garden, such as Fragaria virginiana, the plants could attract 69 species of native butterflies and moths, in addition to native bees and beneficial insects.
The goldenrod in my garden attracts 49 species of native butterflies and moths. My white oak tree attracts 200 species of Lepidoptera. If I added a western chokecherry (Prunus virginiana var. demissa) to my landscape, it could attract 240 species of native butterflies and moths. The website provides pictures of the supported Lepidoptera at different stages of their lifecycle, which makes it easier to know what to look for in my garden.
What about our vegetable gardens? How can they help increase biodiversity in our landscape? It’s interesting to note that although bees are more likely to pollinate fruit crops, Lepidoptera are primary pollinators for many vegetables and herbs, especially those in the carrot, sunflower, legume, mint and Brassica family. Yes, caterpillars eat part of their host plant and can damage our vegetable crops; however, they also attract predators that will provide balance to a healthy garden ecosystem.
European honey bees are generalists, which means they collect pollen from a wide variety of flowering plants. However, plants in the Solanaceae family — tomatoes, eggplant, peppers, potatoes — as well as pumpkins, zucchini, blueberries and cranberries all require bees to stimulate the flower before it will release its store of pollen. This process is called buzz pollination. Honey bees don’t have the right stuff to get the job done, but our native bumblebees and solitary bees do.
Tallamy’s main point in “Nature’s Best Hope” is that one of the biggest mistakes we’ve made in our efforts to protect the natural world, and thus our planet, is that we’ve relegated the important work of conservation to the experts. But in order to effectively address our environmental crisis and restore biodiversity, we must all become conservationists. As Tallamy points out, “We must abandon our age-old notion that humans and nature can’t mix, that humans are here and nature is somewhere else. Starting now, we must learn how to coexist.”
Rhonda Nowak is a Rogue Valley gardener, teacher and writer. Email her at Rnowak39@gmail.com. For more about gardening, check out her podcasts at https://mailtribune.com/podcasts/the-literary-gardener and her blogs at www.literarygardener.com.