Why Native Plants? A Chicagoland Gardener’s Guide to What They Do and Why It Matters

Native Plants in Chicagoland · Part 1 of 7

Walk into almost any garden center in the Chicago area and most of what's on the tables comes from somewhere else: hostas from East Asia, boxwood from Europe, daylilies, burning bush, Japanese barberry. They're popular because they're easy and familiar. But a growing number of Chicagoland homeowners are swapping some of them out for plants that grew here long before any of us did.

This series is a practical guide to doing that on a city lot or a suburban yard. Before we get into what to plant and where to buy it, this first post covers the why: what "native" actually means here, what native plants do that ornamentals don't, and what they honestly can and can't do for you.

What "native" actually means in Chicagoland

A native plant is one that grew in a region before European settlement and evolved alongside the insects, birds and soils that live there. For the Chicago area, that means plants from four main habitats: tallgrass prairie, oak savanna and woodland, and the wetlands and lakeshore dunes along Lake Michigan.

The key word is region. "Native to North America" isn't the same thing. California poppy is a North American wildflower, but it's native to the West Coast, and it does very little for a bee in Logan Square. Mountain laurel is native to the Appalachians and sulks in our alkaline clay. When this series says "native," it means native to northeastern Illinois and the surrounding area.

That doesn't mean everything non-native is a problem. Tomatoes, tulips and lilacs aren't hurting anyone. A few non-natives, though, are genuinely invasive here and crowd out everything else. We'll cover those in Part 2.

The Prairie State has almost no prairie left

In the early 1800s, roughly 22 million acres of Illinois, about 60% of the state, was tallgrass prairie. Today only about 2,300 acres of high-quality original prairie remain, roughly one-hundredth of one percent. Most of it survives in odd places that were never plowed: old pioneer cemeteries, railroad rights-of-way and steep bluffs.

Nobody is going to rebuild the prairie in a backyard. But the plants that made it up are tough, beautiful and well suited to our climate, and the wildlife that depended on them is still here, looking for food. Every yard that includes some of those plants adds a stepping stone across a landscape that's otherwise mostly lawn and pavement.

Why it matters: the caterpillar connection

The strongest argument for native plants is one most people never think about: birds run on caterpillars.

According to entomologist Doug Tallamy at the University of Delaware, about 96% of North American land birds feed insects to their young, and caterpillars are the most important of those insects. Even birds we think of as seed-eaters switch to insects in nesting season. A single pair of chickadees needs somewhere between 6,000 and 9,000 caterpillars to raise one brood. A backyard feeder full of sunflower seeds can't do that job.

Here's the catch: most caterpillars are picky. Many can only eat the specific plants they evolved with. A yard full of East Asian and European ornamentals can look lush and still produce almost no caterpillars, which means it produces almost no baby birds. The most famous example is the monarch butterfly, whose caterpillars eat only milkweed. Lots of less famous moths and butterflies are just as specialized.

How much native planting is enough? One study of suburban yards found that chickadees could only sustain their populations where native plants made up more than about 70% of the plant mass. That doesn't mean ripping everything out. It means natives should be the backbone of the yard, not a token corner.

Keystone plants: the ones that do the heavy lifting

Not all native plants are equal. Tallamy's research found that only about 5% of native plant genera support about 75% of caterpillar species. He calls these keystone plants. A native oak alone can host the caterpillars of more than 500 species of moths and butterflies.

If you only make a few changes, make them with plants from this list. All of these grow well in the Chicago area.

For a keystone list specific to your ZIP code, try the National Wildlife Federation's Native Plant Finder or Homegrown National Park.

Roots, clay and stormwater

Lawn grass roots are typically only a few inches deep. Many prairie plants go much further: compass plant, prairie dock and similar plants grow taproots that can reach 10 to 15 feet. Those roots open channels in heavy soil, add organic matter as they grow and die back, and give rainwater somewhere to go.

That matters in Chicago, where much of the city's sewer system carries stormwater and sewage in the same pipes. During heavy storms the system can get overwhelmed, which is why basements back up and why overflow ends up in the river. A yard that soaks up more of its own rain is a small help on both counts. (Part of this series will cover rain gardens, which take the idea further.)

An honest caveat: "native plants have deep roots" gets oversold. Not every native is a deep-rooted prairie giant, and a woodland wildflower in a shady side yard won't behave like compass plant. But as a group, native perennials and grasses hold soil and absorb water far better than turf.

Less work, eventually

Plants that evolved in northern Illinois already know how to handle our winters, our summer droughts and our clay. Once established, most natives need no fertilizer, little or no watering outside of serious dry spells, and no pesticides. (Spraying pesticides in a garden designed to feed insects defeats the purpose anyway.)

"Once established" is doing a lot of work in that sentence, though. Native gardeners have a saying about perennials: the first year they sleep, the second year they creep, the third year they leap. Many natives spend their first season building roots, so a new planting can look thin and patchy for a while. That first year or two also means regular weeding and watering until the plants fill in.

It's also worth being clear that native doesn't mean wild. A good native garden still gets edged, cut back and occasionally divided. The work just shifts from weekly mowing and feeding to a few bigger sessions a year.

What about "nativars"?

Garden centers increasingly sell cultivars of native plants, nicknamed "nativars": a compact coneflower in an unusual color, a purple-leaved ninebark, a double-flowered bee balm. Are they as good as the straight species?

The research says: sometimes. A University of Vermont study comparing native wildflowers with their cultivars found that roughly half of the cultivars were about as attractive to pollinators as the wild form, and about half were less attractive. Research from Tallamy's lab on trees and shrubs found that most cultivars still fed caterpillars well, with one consistent exception: varieties bred to have red, purple or blue leaves instead of green.

A practical rule of thumb:

• Usually fine: cultivars chosen for size, disease resistance or vigor that still look like the wild plant.
• Be cautious: double flowers (they can hide or replace the pollen and nectar), dramatically different flower colors, and purple or red foliage.
• When in doubt: choose the straight species, often labeled with just its botanical name and no variety name in quotes.

A few common worries

"Won't it look messy?"

It can, if it's planted like a meadow and left alone. It doesn't have to. Clean edges, a defined border, repeated plants in groups and a strip of lawn or mulch in front all signal "this is on purpose." We'll devote a post to making native gardens look tidy on a city block.

"Won't it bring bees near the house?"

It will bring more bees, but most of Illinois' native bees are small, solitary and not interested in people. The aggressive ones at summer picnics are usually yellowjackets, which are wasps drawn to food and garbage, not flowers.

"Do I have to go all-native?"

No. Keep the peonies and the vegetable garden. The goal is to make natives the majority, especially in the trees and shrubs that make up most of a yard's plant mass, and to get rid of the few non-natives that are actually invasive.

Where to start

You don't need a master plan. A few small moves make a real difference:

• This fall: leave the leaves in your beds and leave perennial stems standing over winter. Many insects spend the winter there.
• Next spring: replace one bed or one strip of lawn with native perennials.
• If you have room: plant one keystone tree or shrub. An oak planted now is a gift to the next owner of your house, and the one after that.
• Whenever you can: pull out one invasive shrub, like buckthorn or burning bush, and replace it with a native.

The rest of this series gets specific: what to avoid, when and how to plant, where to buy natives locally, and plant picks for groundcovers, parkways, vines and containers.

Sources

• Illinois Department of Natural Resources, Introduction to Illinois' Prairies
• Illinois Department of Transportation, Prairie Inventory
• National Wildlife Federation, Native Plant Finder
• Homegrown National Park, Keystone Plants
• Missouri Department of Conservation, Compass Plant
• Farm Progress, A Deep Dive into Plant Roots
• White, A. (2016), From Nursery to Nature, University of Vermont
• Baisden, E., Tallamy, D. and Boyle, E. (2018), "Do Cultivars of Native Plants Support Insect Herbivores?" HortTechnology 28(5)