As far as I can tell, there are NO native species of Centaurea in the northeast quarter of the NA. By the northeast I'm including everything east of the Mississippi and north of the VA/NC border. Herbaceous Plants of MD lists 8 species and notes that they are all exotic. If by Black Knapweed, you mean C. nigra, it is NOT Native. Gray's Manual of Botany lists 12 and only the last one C. americana is considered native and its range is west of the Mississippi coming as far east as Missouri.
To: beemonitoring@ yahoogroups. com
CC: beemonitoring@ yahoogroups. com
From: sdroege@usgs. gov
Date: Mon, 14 Apr 2008 10:20:44 -0400
Subject: [beemonitoring] L. chrysurus and Centaurea
Thanks folks for sending in more information about Centaurea issues. There certainly are many railroads in that region. At one time Lehigh Gap had 4 separate lines going through it. At this point they just have 2, one on either side of the river. I think that it might be useful to organize a couple of survey days in the region using RR Tracks as the targeted survey area. I wonder if the native Black Knapweed (an excellent bee plant) has suitable pollen for L. chrysurus. I have assumed that this is the species I see along dry road cuts in the Appalachians. ...but perhaps it is Spotted Knapweed. sam
Sam Droege Sam_Droege@USGS. GOV
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USGS Patuxent Wildlife Research Center
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