Sporobolus cryptandrus (Sand Dropseed)
|Also known as:|
|Habitat:||sun; dry sandy soil; prairies, roadsides, along railroads, savannas, barrens, dunes|
|Fruiting season:||August - October|
|Plant height:||12 to 40 inches|
|Wetland Indicator Status:||GP: FACU MW: FACU NCNE: FACU|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Branching cluster up to 12 inches long at the top of the stem, in various degrees of contraction and expansion from within the uppermost leaf sheath. When fully contracted the panicle is narrowly cylindric, enclosed within the sheath, the expanded portions becoming narrowly pyramidal, 4 to 7 inches long, 1 to 2 inches wide. Branches are compound, the primary branches enclosed in the sheath are appressed, exserted branches ascending to spreading, and secondary branchlets remain more or less appressed to their branch. Typically there are much smaller panicles in the upper leaf axils, 1 to 3 inches long and fully enclosed by the sheath. Branchlets have several spikelets (flower clusters), each lance-elliptic in outline, not much flattened, 1.5 to 2.5 mm (less than 1/8 inch) long, light green to purplish. Spikelets are overlapping along a branchlet but not tightly crowded, and have a single floret.
At the base of a spikelet is a pair of bracts (glumes), both thin, hairless, awnless, lance to egg-shaped with a pointed tip, 1-veined with minute teeth towards the tip end, the lower glume .5 to 1.1 mm long and less than half as long as the spikelet, the upper glume 1.5 to 2.5 mm long, about as long as the spikelet or nearly so. Florets are surrounded by a pair of bracts (lemma and palea), both similar to the upper glume, the lemma 1-veined and as long as the spikelet, the palea 2-veined and as long as the lemma or nearly so.
Leaves and stems:
Leaves are basal and alternate, 2 to 5 mm wide, widest at the base with long taper to thread-like tip, flat or rolled in along the edges (involute), sometimes folded, hairless and smooth except rough along the edges from minute teeth. Basal leaves are 6 to 10+ inches long, stem leaves generally 3 to 6 inches. The sheath is hairless on the surface but with a dense fringe of hairs along the edge and tufts of long, white hairs at the tip on both front and back. The ligule (membrane where the leaf joins the sheath) is a fringe of short hairs. Nodes are smooth.
Stems are hairless, erect to ascending or sometimes prostrate from the base then rising toward the tip (decumbent), single or multiple from the base, forming loose to dense clumps.
Exposed spikelets turn straw-colored at maturity, enclosed spikelets often become dark gray to colorless and nearly transparent. Mature florets drop off individually leaving the glumes behind on the stalk, but they eventually drop off, too. Grains (seeds) are gray to brownish, irregularly oval to oblong, .75 to 1.2mm long, somewhat flattened with a large darkened germ on one side.
As its name implies, Sand Dropseed is frequently found on the driest of sandy soils, often in disturbed areas such as roadsides and railroad rights-of-way. Its form is somewhat variable, from sparsely leaved, single stems to fairly densely clumped with multiple stems. This variability can also be observed in the florets and grains. Some populations I've collected seed from produce larger spikelets with grains well over 1 mm and other groups of plants have very fine grains, well under 1 mm, though I've not paid close attention as to how site fertility or moisture may be impacting these traits. Besides the (at least partially) enclosed panicles, Sand Dropseed is otherwise identified by the single-flowered, awnless and hairless spikelets 1.5 to 2.5mm long, the upper glume, lemma and palea all nearly the same length with a short lower glume, and the dense tufts of long hairs around the tip of the sheath, even on the back.
S. cryptandrus is most similar to Rough Dropseed (Sporobolus compositus), both having their panicles fully to partially enclosed by the leaf sheath. Overall Rough Dropseed is a more robust plant and Sand Dropseed differs with exserted panicle branches spreading out to right angles, becoming open and pyramidal and the dense whorl of spreading hairs at the upper end of the sheath is conspicuous. On Rough Dropseed, the panicle remains tightly contracted even after emerging from the sheath and it lacks the tufts of long, spreading hairs around the sheath tip.
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- sparsely leaved Sporobolus cryptandrus plant
- densely clumped Sporobolus cryptandrus plant
- robust Sporobolus cryptandrus
- Sporobolus cryptandrus plants
- Sporobolus cryptandrus in late fall
- scan of upper stem
- panicle in the sheath
- flowering panicle
Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk taken in Anoka, Itasca, and Ramsey counties.
Have you seen this plant in Minnesota, or have any other comments about it?