A test of my resolve to grow more native plants has taken on a new dimension in my garden this month. Behind my vegetable bed, a stand of three 8-foot-tall sunflowers helped themselves to an open space I hadn’t yet cultivated. I wasn’t really surprised to see them pop up since one took over the vegetable garden itself last year, and when I finally cut it down, I carelessly dropped a few seeds. Why did I let wild sunflowers (a.k.a. weeds) run wild in my veggie garden? True, that raised bed cost me a pretty penny, making it valuable garden real estate, but instead of immediately yanking the “weed,” I decided to observe the interloper for a while instead. My patience was rewarded when I learned that it regularly attracted at least five species of bees!
I probably wouldn’t have gotten away with this science experiment in my front yard because the city has an ordinance against weeds more than 10 inches tall. Heaven forbid I let a “weed'' grow to 8 feet! But in the backyard, I was able to let the experiment run. I’d never even heard of pebble bees until I took photos of them on my sunflower and identified them using the iNaturalist app. In addition to pebble bees, there were metallic green sweat bees,
ligated furrow bees (Halictus ligatus), some kind of leaf-cutter bee (Megachile sp.), and the familiar but imported Western honey bee (Apis mellifera). Additionally, the sunflowers in the FIG garden at Bird’s Fort Trail Park have attracted the American Bumble Bee (Bombus pensylvanicus). This year, I noted a sixth species on my sunflowers—some kind of longhorn bee, but I haven’t been able to get a closer look because it has been hanging out on the topmost flowers, about three feet over the head of this backyard-bug paparazza.
Similar questions of what does or does not constitute a weed and which nonnative ornamentals deserve space in our pollinator garden or what native plants might be too unkempt for a public display garden are frequent subjects of friendly debate during our planning meetings and weeding days at the FIG garden. The cannas are showy and much tidier than sunflowers, but what is their role in the local ecosystem? Until recently, I would’ve been tempted to say they had none, but now I’m more likely to say, “I’m not sure yet.”
A couple years ago, I read Douglas Tallamy’s Bringing Nature Home and was easily converted to his philosophy of gardening with native plants. This entomologist from Delaware lamented that it took him 20 years to see the disconnect between what he had learned in grad school about insect diets with what horticulture professionals had taught him about choosing the best garden plants. His epiphany: “Our native insects will not be able to survive on alien plant species”—the same plant species that we’ve been enthusiastically bringing into our suburban gardens for decades. I could instantly relate. As a student of botany in what now feels like a past life, my ecology classes in the Department of Wildlife and Fisheries had little bearing on my studying of plants, and when bugs were discussed in my plant science classes, they were generally described as pests.
Now it has become popular to try to help the helpful bugs like pollinators and predatory insects that keep the pests in check (a.k.a. beneficials) by growing the plants they like to eat in our gardens. But it’s not just the honey bees that are good pollinators. According to the Jha Lab at UT Austin, there are over 800 species of bees native to Texas, and the journal Science reports that some native bees can be as essential to pollinating crops as the honey bee, sometimes doubling the yields of fruit compared to honey bees acting alone.
But to help support native bees and butterflies, do gardeners like us truly need to grow native plants? In a nutshell, Tallamy’s argument is that native insects have coevolved with native plants, and while some insects are generalists—meaning they’re happy to munch on many plants, native or not—others have very specific diets. When we humans develop land, we’re interfering with those food sources, even if we install a lush garden after a building project is completed. In my own yard, which surrounds a 40-year-old house, I had almost exclusively imported species: St. Augustine grass, red-tipped photinia (which can easily reach the height of my volunteer sunflowers), evergreen hollies, crepe myrtles, Persian ivy, and nandina. Hardly a native plant in sight, and some, like the nandinas, can even pose a danger to local wildlife, namely the mockingbird, our state bird.
I later encountered a dissenting opinion presented by a Smithsonian Magazine article about Tallamy. Entomologist Arthur Shapiro of The University of California at Davis argues that Tallamy exaggerates and catastrophizes, pointing out a number of insects that have adapted to new diets in a much shorter timeframe than Tallamy suggests is possible. To be fair, Tallamy is not advocating anything as extreme as ripping out entire landscapes–he merely asks that when we in suburbia do need to replace our plants, we make more ecologically-informed selections moving forward.
I’ve since tempered my own garden philosophy based on my observations of imported but well-adapted plants that local pollinators appear to enjoy. Solitary bees half the size of honey bees visit my Veronica ‘Royal Rembrandt’ each spring. And the naturalized but essential honey bees love, love, love it when I become a lazy chef and let the basil and oregano form flowers. I recently learned that letting my cilantro bolt and flower made dozens of tiny ant-sized bees I have yet to identify very happy. Native Megachile bees frequent my nearly-native Stokes’ asters from the Southeastern United States each June. And my snapdragon seedlings were absolutely decimated overnight by buckeye caterpillars last fall, despite the flower’s likely origins in the Mediterranean region. This year I even saw eye-catching hummingbird moths frequenting my Burford holly shrubs from China. The hollies don’t have the showiest flowers, so imagine my surprise when I realized that they were actually a functional part of my pollinator garden.
Though I am relieved to see that a number of imported plants do seem to be of some use to local pollinators, Dallas is part of the most endangered ecosystem in North America, and while it isn’t practical and may not even be possible to recreate the Blackland Prairie with its tall grasses and leggy sunflowers in our backyards, planting more natives in our gardens could help stabilize the populations of local pollinators that have survived the upheaval of farming and development.
The FIG mission is to feed the pollinators, so we are letting our observations guide us. The most important thing is to pay attention–look to see what kinds of bugs your plant selections are attracting and supporting–and use those observations to make informed choices about what to add to your garden next. We’ll keep posting about our pollinator sightings from the FIG garden and our home gardens around DFW, and we invite you to share your own pollinator observations in the comments section.
Cultivar: This term is used to refer to a cultivated variety of a plant, which may be either native to our geographic region or nonnative. Wherever it came from originally, it has been selected for its good qualities (an exciting flower color or a tidier growth habit, for example) and modified either a little or a lot by humans through selective breeding. Because of this, cultivars may not form viable seeds, which may or may not be a good thing, depending on your personal gardening philosophy. An example is 'Royal Rembrandt,' a named and marketed variety of the plant species Veronica longifolia.
Near-native: I used this term to refer to my Stokes’ asters because technically they're not a part of the Blackland Prairie ecosystem, but they are native to the southeastern United States.
Adapted: These plants are not from Texas, but they thrive in our region. If you are serious about selecting native plants, you’ll need to do some research because many nurseries and plant guides don’t differentiate between native and adapted plants, especially if they are focused on promoting water conservation. On the one hand, adapted plants tend to be drought-tolerant, so they’ll need less water. On the other, they may not be helpful to local insects. Examples of common adapted plants are Crepe Myrtle (Lagerstroemia indica) and Butterfly Bush (Buddleia davidii), which are both from Asia.
Blackland Prairie: This narrow ecoregion runs north to the Red River and south to San Antonio, cutting right through Dallas. Unfortunately, only small remnants of the original untouched prairie remain, making it the most endangered ecosystem in North America.
Cross Timbers: This ecoregion occupies the west side of DFW. It meets with the Blackland Prairie along the Elm Fork of the Trinity River.