Patience, and the use of native plants, are a big boost to wildlife biodiversity.
By Lisa Casey, ASLA
The Lurie Garden buzzed with life under the summer sun when I visited last July. As I explored this more than three-acre garden in the middle of downtown Chicago, its vibrancy was a surprise. When the horticultural team accompanying me pointed out a native male two-spotted longhorn bee that did not sting, I was transfixed. Never had the garden seemed this alive on past visits.
Originally, biodiversity was not an explicit goal for the Lurie Garden. GGN, in collaboration with Piet Oudolf, drew inspiration from Chicago’s historical landscape communities, an approach that Kathryn Deery, the garden’s head horticulturist, observes was perfectly suited to support biodiversity.
By coverage, about 66 percent of the plants at the Lurie Garden are native. This number closely aligns with the 70 percent required to support wildlife, as identified in a 2017 study by the conservation scientist Desirée Narango and others. The study connects high percentages of native plants to the success of chickadees nesting and raising healthy broods of chicks, highlighting that nesting chicks need insects to eat, and native insects need native plants to thrive. As the ecologist Douglas Tallamy explains in Bringing Nature Home: How You Can Sustain Wildlife with Native Plants, each plant species has a unique leaf chemistry, which, among other things, discourages or prevents insects from feeding on the leaves. Insects have evolved adaptations to overcome these plant defenses, but they are highly specific and often incompatible with nonnative plants.
Zoe Goulet has also noticed the vibrant biodiversity in the Lurie Garden. She worked there as part of a horticultural summer apprenticeship, which included mentorship, a self-directed project, and a presentation to GGN, in addition to many hours spent in the garden. Though she observed a wealth of insects besides the typical honeybee and other common bugs, few others had done so, a phenomenon the garden’s horticultural team calls “bug blindness.”
The biodiversity crisis is often communicated in the abstract or as aggregate data. For example, a 2021 study sponsored by the British government notes a nearly 70 percent drop in the global abundance of mammals, birds, fish, reptiles, and amphibians since 1970, but it can be difficult to ground these numbers in everyday impacts. Food systems are at least a starting point. Fresh water, clean air, healthy soil, and other essential resources that support effective food production come through functioning ecosystems that run best in the presence of diverse groups of species.
Where bug blindness sits within this system became clearer when I encountered the statistic—in a study led by the biologist Yinon Bar-On—that the biomass of all wild mammals and birds is outweighed by the biomass of humans six to one, and by the biomass of livestock 11 to one. While the study did not break out the biomass of insects from the larger category of arthropods, insects are the foundational link between plants and wild vertebrates in the food web.
To help the public and garden volunteers overcome bug blindness, Goulet created an insect directory based on her research and observations from mid-April to the end of July 2024. The intent was to highlight insects that are the most prevalent in the garden and the most recognizable to the public, such as butterflies, bees, wasps, beetles, and flies. Goulet sought input on identifying the insects from Nick Dorian, a pollinator ecologist researcher at the Chicago Botanic Garden; Kelly Kinnerk, a horticultural assistant at the Shedd Aquarium; and Heather Holm, a conservationist and author. The result is a well-researched guide for the public to use this summer. Visitors to the Lurie Garden are also encouraged to submit their observations to iNaturalist, which has documented more than 30 native insect species in the garden through research-grade observations, sightings that have been verified by the iNaturalist community.
Goulet said that insects are the foundation for attracting birds and other wildlife, and so far, the iNaturalist research-grade observations have recorded 14 native bird species. Their broods need thousands of caterpillars (Tallamy has found that a chickadee clutch needs to eat between 6,000 and 9,000 caterpillars before the nestlings mature) and other insects for food, the consumption of which can minimize insect damage in the garden. The horticultural team at the Lurie Garden understands that leaves are also food and that minor damage signifies a healthy ecosystem. An indicator of biodiversity success is the number of insect predators, such as the eastern cicada-killer wasp, as well as hawks, rodents, coyotes, and foxes. When the garden identified a litter of fox kits in 2022 and 2023, Deery contacted the Urban Wildlife Institute at Chicago’s Lincoln Park Zoo, which confirmed their presence, indicating the garden’s success as a functioning ecosystem.
Biodiversity management involves subtle but intentional shifts. Goulet observes that many native insects likely arrived in the soil and leaves of native plants obtained from nearby nurseries. Previously, the garden set aside a zone for insect nesting. However, when Holm consulted for the garden, she observed that most of this narrow band was filled with plants that did not support stem-nesting bees, as they did not have the correct stem diameter. These bees require hollow stems with a specific cavity size for suitable nesting. Now when the grasses and perennials are cut back in mid-February, the horticultural team leaves islands of uncut material, such as groups of bee balm and goldenrod, around the garden. These cuttings form a series of circles that Deery feels complement the bulb display. Care is also taken to provide undisturbed ground and leaf litter for ground-nesting bees.
To help landscape architects support insects in their project designs, Goulet suggests specifying keystone plants such as goldenrod, rattlesnake master, coneflower, and oak, which support a large number of insect species at various stages of their life. These plants have a native range across the Midwest and beyond. Small inclusions of such plants, combined with specific maintenance practices such as eliminating or minimizing chemical pesticides, can support non-plant life in a landscape.
on biodiversity. Infographic by Millennium Park Foundation/Lurie Garden.
The Lurie Garden’s approach to integrated pest management requires patience and may not always succeed. When Goulet discovered a small patch of plants containing alliums that showed damage from aphids, she waited to see if an insect predator would arrive and resolve the situation. Possibly because the patch was located near a set of stairs isolated from the larger garden, or because it was sited under a tree with reduced sunlight, none did. The aphids became more entrenched, and the team had to remove the alliums.
Deery explains that one goal of the Lurie Garden is to create something intentional and beautiful: “But we’re also kind of breaking that traditional view of what is beautiful and what is not.” The tagline of the garden is “To create an urban oasis for city dwellers and wildlife alike.” Messaging through social media and volunteers educates visitors on biodiversity and how to bring it into their own gardens. Although the Lurie Garden does not measure its biodiversity, it intends to do so in the future.
About 25 miles north of the city, the Chicago Botanic Garden is using native plants within the even more complex environment of a dynamic shoreline. John O. Simonds designed the gardens in the 1960s to integrate stormwater management through a system of interconnected lakes dotted with islands and to protect the site’s existing natural areas, an approach that provided a foundation for the garden’s biodiversity efforts today.
By the 1990s, the original crisp lawn edges around the islands were crumbling. Fred Spicer, the garden’s executive vice president and director, says, “[P]ieces of the islands were falling into the lakes, heavy clay soils that just slid in big chunks,” and he reports hearing someone say the shoreline “looked like nibbled cookies.” A new approach was in order.
Drawing on the cues to care theory developed by Joan Nassauer in her landmark essay “Messy Ecosystems, Orderly Frames,” Spicer said that the garden shifted its focus to creating defined edges along the shoreline and using abundantly flowering, recognizable plantings instead of a matrix planting scheme, which can feel disordered to visitors. Beginning in 2000, the garden began developing a bio-based infrastructure approach to restore the shoreline that also meets the garden’s aesthetic standards and blends seamlessly with nearby natural areas. At 5.7 miles in length, the shoreline represents the largest single garden approach on the site. Planting all natives along the water’s edge provides a visual connection to the garden’s natural areas and eases maintenance. Not only do high-quality wetlands reduce erosion, but their density of plantings also thwarts invasive species establishment.
Located at the confluence of the Mississippi River and the Great Lakes Basin watersheds, the Chicago area is uniquely positioned ecologically and geologically. Heidi Natura, FASLA, principal and CEO of Living Habitats, who has worked on the restoration efforts for more than 25 years, notes how those characteristics drew early botanists and ecologists to the region, and accordingly, the presettlement record of native plants is exceptional. In the Shida Evaluation Garden, the most recent section to be restored, Natura combined this information with a deep knowledge of the behavior of plant species to mass different species from emergent, wetland fringe, mesic prairie, and upland prairie communities to achieve the required stabilization within the compressed space along the shoreline. The critical strategy was to flatten the submerged wetland slopes with a maximum steepness of 20 percent and ideally as shallow as 10 percent.
The Chicago Botanic Garden ecologists and Natura have developed plant lists with a balance between workhorse species and more specialized ones that increase diversity. One tool they have used is the Floristic Quality Assessment, developed by the botanist Gerould Wilhelm in the 1970s. It is a ranked system of conservation value defined by the specificity of habitat for such variables as soil, hydrology, and sun exposure. A ruderal weed that is invasive would be a zero, while a more specialized plant with a narrow habitat would be a 10. An early successional native plant that reseeds prolifically would be low. Although using a tool that recognizes varying ecological value among native plants is common in restoration ecology, its application in a garden context is less typical and has helped optimize the biodiversity of the shoreline.
The plant list for the Shida Evaluation Garden features a robust assortment of sedges: Carex bebbii, Carex bromoides, Carex hystericina, Carex lacustris, Carex lurida, Carex pellita, Carex stricta, and Carex trichocarpa. The sedges, along with rushes like Juncus effusus and grasses like Sporobolus heterolepis, provide the backbone of the planting design. Cornus alba as well as a zone of grasses provides winter interest. May blooms feature Iris virginica, Geranium maculatum, and Mertensia virginica, among others. June yields to blooming Echinacea pallida, Phlox glaberrima, and Tradescantia ohiensis. July and August, when the shoreline is at its peak, have even more plantings. September closes the seasonal interest with Physostegia virginiana, Rumex verticillatus, and Solidago flexicaulis.
Because of the volatility of a shoreline ecosystem, the design team specified native plant plugs for all the plants. One metric of success has been the phenomenal coverage achieved in the first growing season, which is more than could be accomplished through the less intensive approach of seeding. When completing the report to verify plant coverage for the U.S. Army Corps of Engineers last summer, Natura noticed all the butterflies, insects, and other living things that had returned. She recalls a junior staff member saying it was “like a dream,” and says, “You’re immersed in it when it’s there, and you didn’t even realize what you were missing until you see the magic of it.”
Although putting the magic into metrics is challenging, the Chicago Botanic Garden is doing preliminary work in this area as well. For instance, the garden is already monitoring and supporting a rare and unique insect pollinator in addition to more than 400 other native insects on-site, according to the research-grade observations on iNaturalist. Nick Dorian, who helped Zoe Goulet on her insect directory, also is in the early stages of research on pollinators and the effectiveness of pollinator gardens at the Chicago Botanic Garden. As the landscape architecture profession reduces bug blindness, this research will only improve the impact of that work.
Lisa Casey, ASLA, is a principal at Studio Outside in Dallas.
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