When you walk down the street under the scorching summer sun, you might have noticed a dandelion or two popping up in the sidewalk cracks, or little plants growing under the railroad tracks, creeping along fence lines or even in the alleys.

Curious Citizen Russell Tarvid took note of these hardy neighbors, and wondered what kinds of plants they might be and why they seem to flourish in these particular spots.

Cities might seem like they’d be inhospitable for such greenery, but the rugged plants that grow among Chicago’s urban landscape actually feel right at home. According to Greg Spyreas, a botanist with the Illinois Natural History Survey, some of these plants might have originally been common growing on rocky cliff sides or gravelly riverbanks back in the 1700s, before large-scale destruction of their natural habitats. These places have too little good soil for more delicate plants. Concrete slabs and the edges of buildings provide similar spots nowadays.

Others grow well in the sidewalk cracks or alleys because they flourish in disturbed environments — places that see a lot of change, Spyreas said. In the wild, a disturbance could be caused by trampling, like a bison wallowing around in the dirt, or a natural disaster, like flooding or trees falling over. In the city, Chicagoans create all kinds of disturbed environments as well. We pound the pavement on our daily commutes, tamping the dirt underneath until it’s hard as rock. We constantly dig up land for construction. Sidewalks and roadsides absorb lots of salt and pollutants, which kill soil biota, the tiny organisms living in the dirt that help other plants grow.

Furthermore, the glaciers that carved out the Great Lakes and Chicago melted more recently than others in North America, even if that was thousands of years ago. That has had big implications for our soil. When the glaciers melted, they dumped a ton of sand and gravel onto the southern shores of Lake Michigan. Plants growing in this soil must find water before it drains away through the sand or store it for longer. That also makes them well-suited for sidewalks and streets, which are designed to drain quickly.

To learn more about the kinds of plants that grow in Chicago’s nooks and crannies, we consulted Greg Spyreas, a botanist; Erika Hasle, an ecologist with the Field Museum’s Keller Science Action Center; and Seth Harper, a horticulturist from the Peggy Notebaert Nature Museum. We narrowed down their favorites to make a field guide of ten plants you can find around Chicago. We also learned why they’re well-suited for their urban environment and how they can help (or harm) us.

1. Common Plantain (Plantago major)

Common plantain has a ring of tough, fibrous roots that help it stay anchored in the ground even when it’s kicked or stepped on. Its low-growing leaves can help it withstand mowing too. This plant’s tiny seeds reliably followed European settlers throughout the world, to the point that it’s sometimes called “white man’s footprint.” Wind pollination helps it grow even when it’s separated from other plants of its kind. It’s a foreign plant, but it’s not invasive — it grows in a balanced way with native plants, so it doesn’t disrupt the ecosystem.

Where can you find it?

You’ll find it growing in compacted dirt, often between sidewalk cracks or well-trodden sports fields.

Helpful or harmful?

Helpful — Its roots break apart compacted dirt, which makes soil more livable where it’s too hard for other plants to gain a foothold. Grasshopper sparrows, northern cardinals and other songbirds eat its seeds. Herbivores like rabbits or deer also eat its leaves.

2. Common Violet (Viola sororia)

Common violet has a failsafe for when there aren’t many insects around to pollinate its bright blue flowers. It uses tiny closed flowers underneath their lower leaves to self-pollinate, and then it flings the seeds away in tiny explosions, “like a gunslinger,” Harper said. This can help the plant spread across concrete cracks, over a lawn, or even jumping between garden pots. Common violet also grows from a deep, thick rhizome (an underground stem) that helps it store water in dry environments and spread underground. It’s native to North America and also happens to be the Illinois state flower.

Where can you find it?

Sidewalk cracks, roadside ditches, and creeping around infrequently mowed lawns (especially in shady spots).

Helpful or harmful?

Helpful — In addition to providing food for pollinators, people can eat its leaves and flowers. You can even candy it. (However, the experts warn that Chicago streets have some pretty harsh toxins, so you shouldn’t eat any weed you pull from the sidewalk.) Violets are also host plants for fritillary butterflies.

3. Prostrate Knotweed (Polygonum aviculare)

Its native habitat is rocky European cliffsides, where it uses a long taproot to cling to stones and find water. In Chicago, this taproot helps it pierce sidewalk cement and avoid getting uprooted when kids kick soccer balls over it. One of Chicago’s most common weeds, it likely spread here because it was accidentally mixed in with European settlers’ agricultural seeds.

Where can you find it?

Any disturbed land — especially sidewalk cracks or well-trampled parks. In many sports fields, the “grass” is actually prostrate knotweed. It is one of the only plants that can tolerate being constantly stepped on in rock-hard soil.

Helpful or harmful?

Helpful — This plant is great at finding a way to make life happen in otherwise terrible growing conditions, according to Harper. In nature, it can quickly spread over large plots, but its colonies rarely stay for long. It helps break up compacted soil and provides cover for new plants to grow.

4. Pennsylvania Pellitory (Parietaria pensylvanica)

Pellitory puts all its energy into becoming the best solar panel it can be and doesn’t waste any time on anything else. According to Spyreas, it has papery thin leaves that are jammed full of chloroplasts — the plant cells that help with photosynthesis. This helps it thrive in shady places with little competition from other plants. At the end of summer it creates “a whole flourish of seeds,” Spyreas said. It stores some of those seeds in an underground seed bank, so even if a gardener weed-whacks the stem down early, the hidden seeds can sprout later.

Where can you find it?

Shady places — like under railroad tracks or alongside building walls. This is unique because pellitory is an annual plant (a plant with a one-year life cycle), and most annuals don’t tolerate shade.

Helpful or harmful?

Helpful — Red admiral butterflies can use it as a host plant where they lay their eggs. Like many annual plants, its seeds have a lot of nutrients, making it good food for birds who hang out in the shade.

5. Buckthorn (Rhamnus cathartica)

Grazing animals don’t like its tough, thorny, leathery leaves. A European transplant, it has adapted to withstand cold temperatures, so it greens up in early spring while many native plants stay dormant through May. That means this plant can sprout and use vital soil nutrients before other plants even wake up.

Where can you find it?

Cook County forests, yards, fence rows, waste areas. It especially spreads in the Great Lakes region because it likes that recently glaciated dirt.

Helpful or harmful?

Harmful — It’s by far Chicago’s worst invasive species. A 2020 tree census from the Morton Arboretum reported that 36% of tree stems in the seven-county Chicago region were buckthorn. Anytime an environment is mostly one plant, ecologists don’t like that, Hasle said, because it means that one plant is preventing others from growing. In addition to outcompeting native plants for soil nutrients, it also grows quickly and blocks the sun, which makes it hard for new plants to sprout.

6. Milkweed (Asclepias syriaca)

This plant grows a deep root that also spreads horizontally, which lets it clone itself over distances. It also spreads with fuzzy white seeds that float on the wind. Milkweed is adapted for North American prairies, which gives it strong drought tolerance. Most insects and animals avoid eating it because its leaves contain noxious sap.

Where can you find it?

According to Hasle, milkweed grows basically anywhere it can find sunlight and avoid being cut down. That could be alleys, vacant lots, along railroads, fencelines and more.

Helpful or harmful?

Helpful — Monarch caterpillars famously eat only milkweed leaves. Hasle said urban environments like Chicago could provide a third of the milkweed needed to stabilize the monarch butterfly population if we let the plant grow. Furthermore, when deep-rooted prairie plants like milkweed die, their roots release their nutrients deep into the soil, which creates a better place for new plants to grow.

7. Common Chicory (Cichorium intybus)

Chicory, a European transplant, grows a long tuberous root that’s edible. It has a unique metabolism that allows it to tolerate drought conditions, which also seems to be why it tolerates salt in soil — like the kind that we pour all over the road during the winter in Chicago.

Where does it grow?

When you’re waiting at a stoplight or driving on the highway, you might see it growing along the roadside. It also pops up on sidewalk easements, that grassy strip between the sidewalk and the street.

Helpful or harmful?

Helpful — If you’ve ever been to New Orleans, you might have had chicory coffee. That’s made by roasting this plant’s roots. It can also be fed to dairy cattle, and its flowers provide food for pollinators, too.

8. Canada Goldenrod (Solidago canadensis)

Canada goldenrod, a native prairie plant, has an aggressive, intricate, root system. It grows from a horizontal, hefty rhizome that lets it store food and clone itself until it covers large swaths of land. It can survive in many different environments because its genetics allow it to grow in super flexible, adaptable ways. This trait is called phenotypic plasticity, and it gives goldenrod lots of different appearances. For example, if its habitat is dry, it’ll grow shorter stalks with narrow, fuzzy leaves to conserve water. If it’s in a wet place, it’ll grow lush, thick leaves.

Where can you find it?

Along roadsides, in alleys and vacant lots, along fence lines — where you don’t mow, it can grow.

Helpful or harmful?

Helpful — It provides food for a ton of insects and animals. As a fall bloomer, it’s a useful last source of pollen and nectar for many pollinators before winter starts. While it’s often blamed for fall allergies, it actually has a heavy, sticky pollen spread by pollinators like bees, so it’s not the reason your eyes get itchy. Deep, sturdy prairie roots and rhizomes also help prevent flooding by giving rainwater a channel into the soil “instead of into your basement,” Hasle said.

9. Garlic Mustard (Alliaria petiolata)

Most plants need a network of tiny soil fungi to grow, but garlic mustard can survive in sterile soil — dirt that doesn’t have these fungi. What’s more, it actively releases a chemical to kill any existing soil networks. Its leaves can make a tasty pesto though, Hasle said. It likely spread here as a garden green, Spyreas said.

Where can you find it?

Paths, gardens, fence rows and waste areas, often in some shade.

Helpful or harmful?

Harmful — It’s invasive and creates dead zones where other plants can’t grow. Helpful soil microbes will eventually adapt and reclaim the dirt (over decades), but by that point, many native plants will have been eliminated from the area.

10. Queen Anne’s Lace (Daucus carota)

This naturalized plant grows a deep taproot that turns orange as it ages. This helps it store nutrients and water in dry places. “If you take that root and you crack it in half, it smells like you just took a bite into a carrot,” Spyreas said. That’s because this plant is the wild ancestor to the carrots we know and love in our grocery stores today. According to Spyreas, if domestic carrot seeds spread back into the wild, they start to revert back to their wild Queen Anne’s Lace appearance.

Where can you find it?

Sidewalk cracks, parks, junk yards, on the sides of railroads — “It grows all over the place,” Spyreas said.

Helpful or harmful?

Helpful — In addition to being the ancestor to domestic carrots, it provides food for lots of insects, birds and occasionally mammals. European starlings also use this plant as nesting material, possibly to reduce parasites.

Bonus plant! Because we couldn’t forget…

Dandelion (Taraxacum officinale)

This plant benefits from a long thick taproot that helps it pierce compacted soil and find nutrients. That taproot also helps it resist trampling and weeding. Its rubbery leaves make it even hardier for highly-trafficked areas. Its puffy white seeds are easily spread by the wind and anyone who needs a wish. This plant also displays phenotypic plasticity that’s really easy to see. Sometimes dandelions grow really tall, and other times they grow really short. If you mow your lawn enough, over a few years, you’ll start to see only the short ones keep growing — natural selection in action.

Where can you find it?

It readily pops up in sidewalk cracks, grassy parks, sports fields, sunny roads and railroad tracks.

Helpful or harmful?

Helpful — The entire plant is edible, with its leaves commonly made into spicy salads. You can even make tea or coffee out of its roots. It is “really, really important” for pollinators in early spring, when few other plants are blooming, Spyreas said. “This is important for several endangered bumble bees.” Birds also eat the seeds, and the roots loosen compacted soil.

More about our questioner

Russell Tarvid, an admissions office manager from Frankfort, grew up in Brighton Park. “I have like zero experience with botany,” he said. His only encounters with nature were taking a walk around the neighborhood.

But then he read the book Outside Lies Magic by John R. Stilgoe. “The main theme of it was to just stop and look around at the built environment and just notice things.”

So Russell started taking a closer look around town. He used to work in the Loop, which is definitely not known for its vegetation. That made him pay closer attention to all the tiny plants we’d otherwise call weeds.

“You’ll see this thing growing and go, holy smokes,” he said. “It may sound silly to have admiration for it, but it’s a living thing that somehow found a way.”

Natalie Dalea is Curious City’s multimedia intern. Follow her @nmdalea.

The thumbnail image is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Correction: In a previous version, we listed Tarvid’s job title as admissions counselor. His position is really admissions office manager.