ABSTRACT.  Bloodscale Sedge (CYPSA) is widespread in the Old World, where it has been cited as a rice weed.  It has not been previously reported from North America.  A critical analysis of herbarium specimens shows that North American plants previously identified as the endemic Cyperus louisianensis are indistinguishable from CYPSA.  Since 1993, intensive field surveys have revealed more than 40 populations of CYPSA ranging from southeastern Louisiana to southeastern Georgia along wet right-of-ways and in lawns.  Because CYPSA is often locally abundant and weedy in the United States, it appears to have potential to become an economically important rice weed.  CYPSA plants started from seeds (1994-1996) and from transplants (1994-1995) were maintained in the greenhouse at 30 to 35 C day and 25 to 30 C night, at 60 to 75% relative humidity, without supplemental lighting.  Greenhouse-grown CYPSA plants emerged from mid- and late May until mid-September each year; flowered from late August until mid-December, with peak flowering in early September to early October; and subsequently fruited.  Plants emerging later in the year were shorter at flower initiation than those emerging earlier, suggesting that CYPSA is photoperiodic.  All greenhouse-maintained CYPSA plants died shortly after fruiting, showed no evidence of perennation, and thus consistently exhibited an annual habit.  Additional research is needed to determine the potential range extension of CYPSA in North America and to develop best management strategies should it become a weed problem in rice production in the United States.

Keywords:
Bloodscale sedge
Cyperus sanguinolentus
Cyperus louisianensis