Common reed [Phragmites australis (Cav.) Trin. ex Steud.] is an invasive plant that reproduces poorly by seed but regenerates vigorously by rhizomes. Because Phragmites australis propagates well through rhizome growth, invasion often occurs from transported rhizome tissue. We investigated both rhizome-fragment biomass and seasonal effects on survival and growth of ramets. Rhizomes were collected along roadside ditches during the fall of 2009 and 2010 and during the summer of 2010 and 2011. Fall and summer were chosen because the plants were either dormant or actively growing, respectively. Rhizomes were cut into fragments then grown in a greenhouse for 60 d in vermiculite with no added nutrients. Rhizomes collected in the fall had a survival rate of 71.1%, whereas only 15.6% of those collected in the summer survived. Within season, rhizomes with low initial biomass had lower survival rates and growth than did large rhizomes. There was no seasonal difference in the total biomass produced by the surviving plants; however, allocation of biomass did differ. Summer-collected rhizomes showed a higher belowground to aboveground biomass ratio than did those collected in the fall. Understanding the viability of Phragmites australis rhizome fragments provides land managers a greater awareness of the high-establishment risks of Phragmites australis. This information should be included in an integrated weed management program, and actions should be taken to reduce the spread of this weed during roadside maintenance. Although the risk of survival is lower during the summer, soil contaminated with Phragmites australis should not be transported or must be sifted with a screen to ensure all rhizome fragments are removed.

Nomenclature: Common reed, Phragmites australis (Cav.) Trin. ex Steud.

Management Implications: Common reed [Phragmites australis (Cav.) Trin. ex Steud.] is one of the most problematic invasive species in the country, and it can be found growing in dense monocultures along roadside ditches and right-of-ways throughout the Midwest and eastern United States. It propagates clonally and is often spread when rhizome fragments are transported in soil during ditch maintenance. This research aims to contribute to integrated weed management plans by suggesting cultural practices to reduce the spread of Phragmites australis based on survival and growth rates as a function of rhizome biomass and the season in which the rhizomes are transported.

We determined that even though summer-collected rhizomes have depleted resource stores and the risk of survival and growth is lower, soil contaminated with Phragmites australis rhizome fragments should never be transported. Rhizomes should definitely not be transported in fall because the survival rates and growth are high at that time. We suggest that rhizomes be chipped and that any transported soil be screened to remove the rhizome fragments and thereby lessen any risk of producing a new clonal population.