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Phragmites and cattails

Susan Cordes, Brandon Dawson, Jerilyn Kremer, and Ryan Miller
Conservation Biology class, BIO 345, Biology Department, DePauw University
Spring semester 2006

Invasive species can be a threat to natural ecosystems.  Phragmites australis, an invasive wetland grass, is common throughout the Midwest.   Phragmites is often planted as an ornamental grass in homeowners' lawns, but the plant easily escapes “captivity” and invades natural ecosystems. Phragmites is an aggressive plant, readily outgrowing its competitors in areas with shallow standing water.  Phragmites co-occurs with cattails in the Quarry Bottom of the DePauw Nature Park.  Our goal was to monitor the distribution and abundance of Phragmites and cattails in the Quarry Bottom.

We collected data on three types of patches in the Quarry Bottom:  pure patches of Phragmites, pure patches of cattails, and mixed patches of Phragmites and cattails. We measured the size and geographic location of 37 patches. We used aerial photos and GPS data to generate GIS maps that show the spatial distribution, location, and size of each patch. 

Phragmites patches were larger than mixed patches, which were larger than cattail patches. Phragmites appears to be spreading from a centrally located patch towards the edges of the Quarry Bottom.  The farthest patches from the central Phragmites patch are pure cattail patches, but Phragmites is gradually migrating into cattail patches, converting these into mixed patches.

We recommend that future research be conducted to study the growth, spread, and distribution of the patches. Eradication methods should be used to deter Phragmites from displacing cattails.  Methods of eradication include application of herbicides, pulling, mowing, burning, increasing salinity in the water, and flooding.  However, care must be taken with all types of eradication, because not completely removing all Phragmites will allow it to come back, and some types of eradication, such as application of non-restrictive herbicides and burning, can harm surrounding cattails and inhabitants of Phragmites.