Cyperus plukenetii Fernald - Plukenet's Umbrella Sedge

Cyperus plukenetii plant

Family - Cyperaceae

Stems - Aerial stems to -1m tall, about 2-3mm broad, erect, herbaceous, trigonous (blunt), uniformly pubescent and roughened over their entire length, from very short, knotty rhizomes.

Cyperus plukenetii baseBase of plant.

Cyperus plukenetii stem

Leaves - Blades to 60cm long, 3-7mm broad, all basal, present at anthesis, pubescent.

Inflorescence - Terminal umbel with 4-12 rays. Each ray to 15cm long, uniformly roughened and short pubescent over the entire length, 1-2mm broad. Bracts of the inflorescence +/-6, shorter than the rays, pubescent at least on the margins, spreading. Spikes 10-18mm long, with 20-100 spikelets. Spikelets dense, sessile, mostly reflexed, the bases of the spikelets not visible.

Flowers - Spikelets 6-8mm long, narrowly linear, acute to acuminate at the apex, terete to somewhat 4-angled, typically with 3 scales, glabrous, typically shed as an intact unit. Scales 4-4.5mm long, strongly overlapping, lanceolate, acute to acuminate, straw-colored to brown. Fertile florets 1-2 per spikelet. Stamens 3. Anthers .5-1mm long. Stigmas 3. Fruits 2.5-3mm long, narrowly oblong in outline, 3-angled in cross-section, with flat sides, brown, shiny, finely pebbled.

Cyperus plukenetii flowers

Flowering - July - September.

Habitat - Sand prairies, openings of dry upland woods.

Origin - Native to U.S.

Other info. - This species can be found in just a few southeastern Missouri counties. The plant can be identified by its dense spikes and pubescent-roughened stems and inflorescence rays.
Another species, C. retrofractus (L.) Torr., is similar but has sharply trigonous stems and inflorescence rays that are smooth to slightly roughened at the apex. This latter species is found in the same area of Missouri as C. plukenetii.

Photographs taken at Fort Benning, GA., 8-11-05.


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