Aristida ternipes

Spidergrass

Field view by James Bailey (in www.iNaturalist) of Spidergrass panicles. The stiff branches stand way out from the stem.

Lower part of the panicle is straighter and more congested, with thin leaves.

Both the stems and the leaves are long and thin. This grass can grow four feet high

The branches are so long and stiff that the grass won't lie flat for a photo.

The long, sparce, stiff branches are bare below the typical cluster of spikelets.

Two florets with only one longer awn and no twist below it. You can see the tiny second awn of this atypical "three-awn."

How to Identify Spidergrass

Spidergrass, a perennial, usually stands stiffly erect. It's branches look thin--each consists of a bare strut, then an elongate seed bunch (spikelets), and then often a further long extention in the form of an awn. There may be one or two other awns, very short, that emerge beside the longer one--see last photo.

Similar Species

  There are only a few knee-high to chest-high spindly grasses that have such stiff branches that the grass specimen won't lie flat on its side but stands up on its branches. Spidergrass is one; Switchgrass (Panicum virgatum) is another, much different looking.

  The closer look-alike is Poverty Three-awn, (Aristida divaricata), a close relative. It is usually shorter, about knee-high, and looks just like Spidergrass. Two things give Poverty Three-awn away: (1) Poverty Three-awn has the basal strut that holds the three awns twisted about four times, while Spidergrass does not. (2) Poverty Three-awn has lots of long hairs at the junction of sheath and leaf blade (where the leaf blade extends outward from the stem), while Spidergrass does not. You can pluck the floret, with its straight or twisted awn-base, out from between the long, thin, papery glumes. Then, using your hand lens, look for the four or more twists to prove it is Poverty Three-awn.

  Details for completeness: in choosing between Spidergrass and Poverty Three-awn, if your grass happens to be taller than two feet four inches, my mid-thigh, it is Spidergrass, the taller of the two. Also if your grass has only one long awn per spikelet and maybe one or two tiny stubs, or if the tiny anthers are only 0.8 to 1.0 millimeters, it is certainly Spidergrass.