Invasive Plants in Illinois
Check your property for the Japanese Honeysuckle and Multiflora Rose, two of the most invasive plants in Illinois. Here’s a full list.
Written by Jennifer Justice
Reviewed by Melanie Reiff
From Japanese Honeysuckle to the Eurasian Watermilfoil, these are the 15 top invasive plant species in Illinois.
Illinois is home to a thriving culture, some of the best food in the Midwest, and big-name sports teams. But if you're thinking about moving to Illinois (or already live there), it's important to watch out for invasive plants that could be dangerous to you, your home, or your property value!
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The top 10 invasive plant species in Illinois
1. Japanese honeysuckle
Scientific name: Lonicera japonica
What it looks like: Reddish-brown climbing vine with oval-shaped leaves, yellow or white flowers, and round, black berries.
Why it’s a problem: This aggressive vine overgrows trees, shrubs, and flowering plants. This species creates a thick wall of foliage that blocks light for other plants, killing whatever is under its shade. Its relative, the Amur Honeysuckle, is also a threat.
What to do: Dig out vines by the roots and apply herbicide to the area.
2. Multiflora Rose
Scientific name: Rosa multiflora
What it looks like: A shrub with oval, serrated leaves, white flowers, and small red hips (fruit).
Why it’s a problem: This species was originally used as a living fence. Unfortunately, it grows in dense patches that overtake everything. It competes with local plants for nutrients and grows fast.
What to do: Use a chainsaw or brush cutter to cut back growth. Herbicides can be used, but avoid contaminating shrubs or trees you want to keep.
3. Autumn Olive
Scientific name: Elaeagnus umbellata
What it looks like: A woody shrub with green and silver leaves, with small yellow flowers. It can grow as tall as a tree.
Why it’s a problem: It can spread quickly and take over forest floors, especially in young forests or newly planted trees. It displaces native plants and is a threat to forest conservation.
What to do: Heavy machinery is recommended due to its deep root system, followed by herbicides since Autumn Olive quickly regrows.
4. Japanese Stiltgrass
Scientific name: Microstegium vimineum
What it looks like: A sprawling grass with spear-shaped leaves that have a silver line down the middle.
Why it’s a problem: It grows as ground cover, but not the kind you want. It takes over ditches, trails, and even fields. Since deer do not eat the grass, it survives foraging by local wildlife.
What to do: Fortunately, you can use a mower or weed wacker to take care of the grass. You can then use an herbicide on the area.
5. Cutleaf Teasel
Scientific name: Dipsacus laciniatus
What it looks like: It grows almost as high as a shrub and produces “bottle brush” flowers.
Why it’s a problem: This flowering plant may look nice, but it outgrows nearby plants. It can survive in poor soil and take over prairie land, pushing out native plants that already struggle to survive.
What to do: Cut off the flower, then chop the rest of the plant off at ground level. It's also a good idea to use herbicide (carefully) in case you didn't notice the flowering plant fast enough.
6. Tree of Heaven
Scientific name: Ailanthus altissima
What it looks like: This tree has a grayish bark, with triangular leaves that grow in a row. The tree produces yellow flowers, and some people claim the tree smells like rotten peanut butter.
Why it’s a problem: The ironically named Tree of Heaven produces chemicals that make it difficult for anything to grow around it, literally killing off its competition. It also loves to grow in groups.
What to do: Unfortunately, this tree takes revenge when you try to cut it down because that encourages the roots to produce more saplings. Avoid taking a knife or saw to it; aggressive chemical treatments are recommended instead.
7. Himalayan Blackberry
Scientific name: Rubus armeniacus
What it looks like: Shrub with woody stems and thorns, serrated leaves, and blackberry-like berries.
Why it’s a problem: You can probably guess what happened—this plant was brought over for food, but things didn't go as planned. It grows fast enough that it's hard to control, and it is a serious fire hazard since it produces a lot of dry branches.
What to do: Don’t plant it as a blackberry alternative! If you run across it, dig it up by the roots and apply herbicide. Cutting it down won’t work since it grows too quickly. Remember, this is a fire hazard, so get rid of it fast!
8. Poison Hemlock
Scientific name: Conium maculatum
What it looks like: It produces clusters of white flowers similar to Queen Anne's lace, while the leaves resemble ferns.
Why it’s a problem: It is poisonous, and even skin contact is dangerous. In addition, it can kill animals if they eat it, so farmers need to be careful that it does not grow in their fields.
What to do: Do NOT touch or burn this plant—even inhaling the fumes is dangerous. Wash your hands immediately if you come into contact with the plant. This is where herbicides are best. You can let the chemicals do the work and steer clear of the plant at the same time.
9. Oriental Bittersweet
Scientific name: Celastrus orbiculatus
What it looks like: Thin silvery or reddish-brown vines with round leaves and red seeds that look like tiny berries.
Why it’s a problem: The entire plant is poisonous, so do not attempt to eat those bright red seeds! In addition, the vines wrap around trees so tightly that it strangles the host tree, while the weight of the vines can break off the branches.
What to do: You need to catch this nasty vine before it takes over. Cut as much of the vines away from the tree or building as possible, then apply herbicide. You will need to recheck the area regularly to catch new growth.
10. Garlic Mustard
Scientific name: Alliaria petiolata
What it looks like: Wispy flowering stems with heart-shaped leaves and tiny white flowers.
Why it’s a problem: While it sounds like something you want to add to your spice rack, young garlic mustard plants can be toxic. It grows fast and produces chemicals that prevent other plants from moving in on its territory, so it kills off anything nearby. Unfortunately, it is also harmful to several rare butterfly species.
What to do: Fortunately, you can pull the plants up by the roots like any weed and treat the area with herbicides. Use gloves and avoid touching your face or eyes in case you are sensitive to the irritants in the plant.
The five most invasive aquatic plants in Illinois
Here are five top Illinois invasive aquatic plants on the watchlist of the Early Detection and Distribution Mapping System, created by the Center for Invasive Species and Ecosystem Health.
1. Eurasian Watermilfoil
Scientific name: Myriophyllum spicatum
What it looks like: Delicate, thread-like leaves that grow in bunches
Why it’s a problem: It smothers native plants and produces dense mats that interfere with leisure activities like boating. It makes it hard for fish to feed, so recreational fishing is impacted.
What to do: Rake or cut away the plants as a temporary solution. Certain types of algae prevent the plant from germinating, and the algae is an excellent food source for fish. Herbicides can also be used.
2. Curly Leaf Pondweed
Scientific name: Potamogeton crispus
What it looks like: They look like miniature kelp, with translucent, curly-edged leaves.
Why it’s a problem: While the scientific name might make you chuckle and they look like the perfect accessory for your fish tank, these plants are harmful. This plant clogs up the water to the point of interfering with recreational activities and kills off native species.
What to do: Rake up or cut away any plants you can reach, then treat with herbicides.
3. Purple Loosestrife
Scientific name: Lythrum salicaria L.
What it looks like: Tall, flowering plant with purplish-pink flowers that grow in a long cluster at the top of each stem.
Why it’s a problem: While it looks like a garden flower, it invades wetland areas, marshes, and ditches. It grows in dense patches and reproduces quickly due to the sheer number of seeds it produces, crowding out native plants.
What to do: You can pull it up by hand. Just destroy the flowers so the seeds don’t spread, then treat the area with herbicide.
4. Brazilian Waterweed
Scientific name: Nymphoides cristata
What it looks like: Bright green, translucent leaves that grow along the steam
Why it’s a problem: This is another water plant that looks like it belongs in your aquarium, but this species grows fast, choking out the native species. As a result, it causes problems for fish and even disrupts recreational activities.
What to do: Rake or cut any plants you can reach, then use herbicide.
5. Narrow-leaved Cattail
Scientific name: Typha angustifolia
What it looks like: Similar to any Cattail, but with narrower leaves.
Why it’s a problem: The Narrow-leaved Cattail is not native to Illinois, which is why it's an invasive species. They grow in stagnant water, unlike other varieties, and they take over resources meant for native plants. This means that the local wildlife loses food sources, and it causes problems by densely packing an area.
What to do: Like most water-based invasive plants, pull it up when you find it. You can also use herbicides.
How to save on homeowners insurance in Illinois
These invasive plants are a big threat to Illinois's natural environment, and most pose a risk to homeowners too.
We can’t help you manage your garden, but
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