What Not to Plant (and What to Pull): Invasive Plants in Chicagoland Yards

Native Plants in Chicagoland · Part 2 of 7

In Part 1, we covered why native plants matter. This post is the other half of the equation: the plants that actively work against a healthy yard, a handful of which are still sold at garden centers all over Chicagoland.

It's worth saying up front: non-native and invasive aren't the same thing. Most non-native garden plants, like tulips, peonies, tomatoes and lilacs, stay where you put them. An invasive plant is one that escapes, usually by seed carried by birds or wind, and takes over natural areas, crowding out the native plants that wildlife depends on. Those are the ones this post is about.

Why invasive plants are such a problem here

Invasive plants succeed for the same reason they cause damage: almost nothing here eats them. Our native insects didn't evolve with them, so they grow unchecked, and they often leaf out earlier in spring and hold their leaves later in fall than native plants, shading out everything underneath.

The scale in the Chicago area is hard to overstate. The Morton Arboretum's 2020 regional tree census found that European buckthorn alone makes up more than a third of all the trees in the Chicago region, and woody invasive plants together account for more than 45%.

Your yard is part of that picture. Birds eat berries from invasive shrubs in city and suburban yards and drop the seeds in forest preserves, along the river and in parks. Removing invasives at home cuts off the supply.

What Illinois law says

Under the Illinois Exotic Weeds Act, it's illegal to buy, sell, distribute or plant any plant on the state's official exotic weeds list without a permit. In October 2025, the Illinois Department of Natural Resources added nine species to that list, including tree of heaven and garlic mustard. Callery pear, the species that includes the Bradford pear, was also added, but its ban doesn't take effect until January 1, 2028, to give growers time to sell off their stock.

A few things the law doesn't do:

• It doesn't require you to remove listed plants already growing on your property. Removal is strongly encouraged, but it's voluntary.
• It doesn't cover every invasive plant. Burning bush and Japanese barberry are both considered invasive in Illinois and are being reviewed by the state's Invasive Species Council, but as of this writing they're still legal and still easy to buy.

The takeaway: "they sell it at the garden center" isn't a reliable sign that a plant is safe to grow.

Shrubs and trees to avoid, and what to plant instead

These are the woody invasives you're most likely to find in a Chicagoland yard, along with native replacements that fill a similar role.

You don't need to cut down a mature shade tree tomorrow. For established trees, the realistic goal is to stop planting more and to choose natives when it's time to replace one.

Groundcovers and vines to rethink

Some of the most common "low-maintenance" groundcovers in Chicago yards are the ones ecologists worry about most, because they form dense mats that nothing else can grow through and escape into woodlands.

• Wintercreeper (Euonymus fortunei): evergreen groundcover and climbing vine. Under state review.
• English ivy and periwinkle (vinca): both spread aggressively into shady natural areas.
• Oriental bittersweet and Japanese honeysuckle vine: both banned. Bittersweet can strangle trees.
• Asian wisterias: beautiful, but they get enormous and spread well beyond the arbor.

Good native replacements include wild ginger, Pennsylvania sedge and woodland phlox for shade, and trumpet honeysuckle or Virginia creeper for vines. Parts 5 and 7 of this series cover groundcovers and vines in detail.

Weeds worth pulling on sight

These aren't plants anyone buys on purpose, but they show up in beds, alleys and shady corners across the region.

Garlic mustard

A woodland weed with small white four-petaled flowers in spring and leaves that smell like garlic when crushed. Each plant makes thousands of seeds, and it can still ripen seed after it's pulled. Pull it in spring before it sets seed, bag it and put it in the trash, not the compost.

Lesser celandine

Glossy heart-shaped leaves and yellow buttercup flowers that carpet shady yards in early spring, then vanish by summer. Small bulbs and root pieces each grow into new plants, so it has to be dug out completely and thrown away. Don't compost it or put it in yard waste.

Dame's rocket

Purple, pink or white flowers in late spring that look a lot like native phlox. The easy tell: dame's rocket flowers have four petals; phlox has five. It's a common ingredient in wildflower seed mixes (more on that below).

Poison hemlock and teasel

Both are banned and both turn up in vacant lots, rail lines and neglected corners. Poison hemlock looks like Queen Anne's lace but has purple-blotched stems, and every part of it is toxic. If you find it, wear gloves and long sleeves, or have a professional remove it.

The problem with "wildflower" seed packets

The colorful wildflower mixes at big-box stores and garden centers look like an easy way to help pollinators. Unfortunately, most of them aren't what they seem.

"Wildflower" just means a flower that looks wild. It doesn't mean native, and it definitely doesn't mean native to Illinois. When University of Washington researchers grew out 19 commercial wildflower mixes, every one of them produced between 3 and 13 species considered invasive somewhere in North America, and some mixes didn't list their contents accurately, or at all. Bachelor's buttons showed up in about three-quarters of the packets. Dame's rocket was another regular.

Even the "good" plants in these mixes are often native to somewhere else, like California poppy from the West Coast. And many are annuals: they put on a show the first summer and are mostly gone by the second, which is the opposite of how a native perennial planting works.

How to read a seed packet:

• No species list? Skip it.
• Check the botanical (Latin) names. Common names are too vague to judge.
• Watch for red flags: bachelor's button (Centaurea cyanus), dame's rocket (Hesperis matronalis), oxeye daisy (Leucanthemum vulgare), California poppy (Eschscholzia californica), baby's breath and cosmos.
• Be skeptical of "regional" labels. A "Midwest mix" without a species list tells you nothing.
• Better option: buy native seed from a specialist that lists every species and sources from the region. Part 4 covers where to find them.

Not everything in a wildflower packet is a weed, but very little in a typical mix will do what a native planting does.

Removing invasives: the basics

Timing: late fall and winter are ideal for invasive shrubs. Buckthorn and honeysuckle hold their green leaves well after native shrubs have gone bare, so right now is the easiest time of year to spot them. Herbaceous weeds like garlic mustard are best pulled in spring, before they go to seed.

Small plants: pull seedlings and saplings by hand when the soil is moist, getting as much root as you can. A weed wrench helps with stems up to an inch or two thick.

Large shrubs: buckthorn and honeysuckle resprout vigorously from a cut stump. Land managers typically cut them near the ground and immediately treat the stump with a herbicide labeled for that use. If you go that route, follow the label exactly. Otherwise, expect to cut the resprouts repeatedly, or hire a landscaper experienced with invasive removal.

Disposal: anything with seeds or berries, plus garlic mustard and lesser celandine, goes in the trash. Woody stems without berries can go out with yard waste.

Replace as you go: bare soil invites the next weed. If an invasive hedge is providing privacy, take it out in sections and replant as you go rather than clearing it all at once.

Sources

• Illinois Department of Natural Resources, Regulations for Exotic Weeds (17 Ill. Adm. Code 1100), effective Oct. 1, 2025
• University of Illinois Extension, Nine new invasive species regulated in Illinois
• University of Illinois Extension, The far-reaching effects of invasive landscape plants
• The Morton Arboretum, Invasive plant species are choking the Chicago region
• The Conservation Foundation, Common Invasive Plants in Illinois
• University of Washington, Wildflower seed mixes full of weeds