Mile-a-minute weed or devil's tearthumb (Polygonum perfoliatum, syn.  =  Persicaria perfoliata) is an invasive annual vine in the Mid-Atlantic and Northeastern United States that reproduces solely through seeds. Our study aimed to identify how mile-a-minute seed viability is affected by time of year and the maturity of the fruit surrounding the achene. Full-sized immature (green) and mature (blue) fruits were collected from five field sites every 2 wk over a 3 mo period, and seed viability was assessed using a triphenyl tetrazolium chloride (TZ) assay. At the onset of seed production in mid-August, 35% of seeds from immature fruits were viable. This percentage increased steadily, peaking at 84% in late September before declining at some sites around the time of the first frost. In contrast nearly all seeds with mature fruits (96%) were viable at all collection dates. Thus land managers who apply physical or chemical control methods for mile-a-minute weed should do so before the onset of any seed production and not simply before fruit maturation. If it is necessary to apply control methods after fruit set, it should be done as early in the season as possible.

Nomenclature: Mile-a-minute weed; devil's tearthumb; Persicaria perfoliata (L.) H. Gross; Polygonum perfoliatum L., POPE10.

Management Implications: This study highlights two important implications for managing the invasive vine mile-a-minute weed (devil's tearthumb) using either chemical or physical control methods. First, mile-a-minute seeds surrounded by immature fruits were shown to be viable to some extent throughout the entire season of seed production. Therefore, physical and chemical controls should be applied before any full-sized immature (green) fruits are produced and not just before mature (blue) fruits are present. Second, the viability of seeds in green fruits increased throughout the season, peaking before the first frost. This indicates that if it is necessary to apply physical or chemical control methods during the fruiting period, these methods should be applied as early in the season as possible, when immature fruits are less likely to contain viable seeds.