Coefficient of Conservatism:
Coefficient of Wetness:
PHILADELPHIA PANIC GRASS
B. S. Walters
Known only from the Maxton Plains of Drummond Island, in thin soil over dolomite pavement, where collected by S. N. Stephenson in 1995. In the Great Lakes region, almost entirely confined to rock barrens, mostly limestone or dolomite pavement (alvar), but sometimes rocky shores and granite pavement. Though it will invade old stone quarries, it is otherwise rarely weedy.
It has an upright habit, branching mostly from the base, and a clearly exserted primary panicle at maturity. Immature specimens with the panicle not fully exserted can be distinguished from P. gattingeri, which has similar sized spikelets (1.8–2.3 mm in P. philadelphicum vs. 1.9–2.4 mm in P. gattingeri), by the blade of the flag leaf (upper most leaf of the main stem) being usually less than 1/2 the length of the primary panicle and the pedicels of the spikelets showing a dramatic increase in hair length just below the spikelet. In P. gattingeri, the flag leaf blade is more than half the length of the panicle (mostly 3/5 as long to even exceeding it in Michigan material) and there is no dramatic increase in pedicel hair length.