Wetland Invasives

Common Wetland Invasives In Our Watershed

Common Reed

Phragmites australis

In Indiana, a tall, non-native grass called common reed aggressively invades wetlands. It forms dense thickets that displace native plants, alter water flow, and block sunlight, harming the local ecosystem. This invasive species can grow up to 15 feet tall with fuzzy flowers and spreads rapidly, often forming large single-species patches. Methods like herbicides and burning are used to control it.

Click here for a useful guide on phragmites

Purple Loosestrife

Lythrum salicaria

It pushes out local plants, which means less food and shelter for native animals like birds and fish. It grows very fast and creates thick patches where only it can survive. It likes wet places like marshes and stream banks. Cutting it won’t kill it. The best way to get rid of it is to use special weed killers, herbicides in the summer when it’s flowering.

Reed Canary Grass

Phalaris arundinacea

The invasive nature of this species is driven by its aggressive growth, allowing it to create dense, thick stands that suppress native plants. Its effective dual dispersal mechanisms – seeds and underground rhizomes – enable rapid spread. Ecologically, it can dominate wetlands, diminish biodiversity, and harm natural ecosystems.

Purple Loosestrife

Lythrum salicaria

Are Cattails The Problem?

Cattail marshes are more than just scenic; their extensive root systems help prevent erosion and absorb pollutants. They also provide crucial habitat for wildlife, serving as cover for fish and shelter for animals and birds. The native Broadleaf cattail is a particularly well-behaved species that forms less dense colonies, though it can cross with other types to form a hybrid.

Unfortunately, many of the cattails seen in our watershed today are non-native, invasive Narrow Leaf and Hybrid varieties. These aggressive competitors quickly dominate wetlands and waterways, displacing native plants and reducing biodiversity. Their dense growth impedes water flow and destroys habitat. They spread rapidly through seeds and underground rhizomes, forming thick mats that prevent other plants from growing.

It can be difficult to distinguish between these species in the wild. The main differences between the invasive Narrow-leaved Cattail and the native Common Broadleaf Cattail are their leaf sizes and flower spikes. Cattails have two parts to their flower spikes (male and female): the pollen is in the upper part (male) and spills down to the lower part where seeds are formed (female). In the invasive Narrow-leaved cattail species, there is a gap along the stem between these two floral components. In the native species there is no gap, just one long connected flower spike. The leaves of Narrow-leaved cattail (invasive) are 2-5 ft long and very narrow.

Broadleaf: 14-23 mm wide, shorter than flower spike.

Narrowleaf: 4-10 mm wide, taller than flower spike.