Common Reed Phragmites australis
Where It's From & How It Got Here
Europe likely accidentally in ballast water from ships
What It Looks Like
2- to 2.5-inch-wide grey-green leaves 8 – 15 inches long; distinctive purple-brown plumes at tips of stalks appear late July; grows 6 – 15 feet tall with 80 percent of mass underground
What It Does
Also called phragmites, this perennial overtakes wetlands and shorelines, creating tall, dense stands. It primarily spreads by rhizomes (horizontally growing stems at or below the surface) and root fragments. Each rhizome can spread over 60 feet and grow over 6 feet tall per year. Roots and rhizomes can accumulate in the soil over 6 feet deep.
Curly Leaf Pondweed Potamogeton crispus
Where It's From & How It Got Here
Eurasia, Africa and Australia from hobbyists in the mid-1880s for use in aquariums
What It Looks Like
3-inch-long oblong reddish-green leaves with wavy, fine-toothed edges; flat reddish-brown stems 1 – 3 feet long
What It Does
The plant spreads via seeds and burrlike winter buds, which move along waterways. New plants form under the ice, making it one of the first invasives to emerge in spring. Dense mats prevent sunlight from reaching native plants and animals below and create problems for anglers and boaters. As the plants decay, they release nutrients into the water that contribute to algal blooms and create foul-smelling messes along the shore.
Eurasian Water Milfoil Myriophyllum spicatum
Where It's From & How It Got Here
Eurasia, Africa and Australia from hobbyists in the mid-1880s for use in aquariums
What It Looks Like
Slender, whorled stems and threadlike leaves, each with 12 to 21 pairs of leaflets; tiny four-petaled or petal-less flowers that grow above the water; four-jointed nutlike fruits
What It Does
The plant is spread by fragments that hitchhike on recreational gear and wildlife. Just one 2-inch fragment can start a new colony. Dense mats prevent sunlight from reaching native plants and animals below and create problems for anglers and boaters.
Flowering Rush Butomus umbellatus
Where It's From & How It Got Here
Eurasia, Africa and Australia from hobbyists in the mid-1880s for use in aquariums
What It Looks Like
Narrow 3-foot-long above-water leaves with triangular cross-sections; three-petaled flowers with three white or pink sepals in distinctive flat-topped sprays atop tall stalks
What It Does
Flowering rush spreads by rhizomes (horizontally growing stems at or below the surface) and root pieces. It's often mistaken for a native rush because it's difficult to identify when it's not flowering.
Purple Loosestrife Lythrum salicaria
Where It's From & How It Got Here
Europe and Asia in the 1800s likely from gardeners or ballast water from ships
What It Looks Like
4 – 7 feet tall with up to 30 purple-flowered spikes
What It Does
Each plant can produce 2.5 million seeds in one year. This hardy, aggressive perennial takes over wetlands and moist soils but offers little food value to wildlife. Unsuspecting people often pick and spread its flowers.
Reed Canary Grass Phalaris arundinacea
Where It's From & How It Got Here
Gulf Coast and Mississippi River basin to southern Illinois likely from illegally emptied aquariums and bait buckets (and possibly restaurants)
What It Looks Like
Smooth, erect flowering green stems 3 – 7 feet tall; leaves 0.5 inch wide and 4 – 8 inches long
What It Does
One of the most aggressive invasives in the Midwest, this plant spreads via rhizomes (horizontally growing stems at or below the surface). It forms dense stands in wet meadows and marshes and around rivers as well as in prairies and woodlands.
