hidden dropseed (rough dropseed)
Sporobolus clandestinus (Biehler) Hitchc.

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plantspikeletillustration

Hidden dropseed is widespread in the southeastern United States, although it is rare in Iowa, where it occurs only in the extreme southeastern corner in prairies on sand ridges. The flowering heads of this species are usually concealed, partially or completely, within the sheath of the leaf immediately below it, so they may be difficult to see, but look for them in Iowa September and October. Hidden dropseed is most similar to rough dropseed (Sporobolus compositus, also known as tall dropseed), but can be easily distinguished by its usually hairy sheaths, much shorter flowering heads, longer spikelets, hairy lemmas, and tapering paleas that are consistently longer than the lemmas.

Etymology: Sporobolus from the Greek sporo = seed and ballein = to throw, referring to the free seeds in many species of this genus that are sometimes forcibly ejected when the usually mucilaginous fruit wall dries; clandestinus from the Latin for hidden, referring to the flowering heads that are at least partly concealed within the leaf sheaths.

 

Plants perennial, tufted, not rhizomatous. Culms (30-) 50-80 (-100) cm tall. Leaves with the sheaths open, the upper ones glabrous, the lower ones mostly papillose-hairy or hairy often only toward the summit, lacking a conspicuous tuft of hairs at the summit; ligules 0.1-0.4 mm long, a line of hairs; blades 7-37 cm long, 1.8-2.3 mm wide, flat to rolled, the lower surface sometimes smooth, more often hairy or papillose-hairy, the upper surface smooth or slightly roughened. Flowering heads terminal and axillary, 4-6 cm long, ca. 0.5 cm wide, contracted, partially or completely enclosed by the subtending leaf sheath; primary branches appressed to the main axis. Spikelets 6-6.7 mm long, usually straw-colored, laterally compressed, lacking any awns; glumes subequal to upper glume slightly longer, glabrous membranous, usually 1-nerved, lower glumes 3.4-4.4 mm long, upper glumes 4.4-5.4 mm long, at least 2/3 the length of the florets; lemmas 5.6-6 mm long, shortly hairy, often only toward the base and margins, 1-nerved, membranous, tapering; paleas 3.6-4.5 mm long, tapering and longer than the lemma, 2-nerved, membranous. Fruits 2-3.5 mm long, ellipsoid, reddish-brown. Chromosome number 2n = 72.

 

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