Flora of North America species comparison

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Calamagrostis porteri

Porter's reedgrass
Habit Plants with sterile culms; loosely cespitose, with rhizomes 5-7+ cm long, 0.5-1 mm thick.
Culms

(60)75-120 cm, unbranched, slightly scabrous;

nodes 2-4(5).
Sheaths

smooth or slightly scabrous;

collars smooth or hairy;

ligules (1)2-5(6) mm, truncate to obtuse, entire or lacerate;

blades 8-40 cm long, (2)3-8(12) mm wide, flat, abaxial surfaces smooth or scabrous, adaxial surfaces smooth or slightly scabrous, occasionally with hairs.
Panicles

(5)10-18(22) cm long, 0.8-3(7) cm wide, contracted to open, often slightly nodding, sometimes erect, green to pale purple;

branches (1.5)2-7(7.5) cm, scabrous, usually spikelet-bearing on the distal 1/2 - 2/3, sometimes to the base.
Spikelets

4-5(6) mm;

rachilla prolongations 0.5-1 mm, hairs 1.5-2(3.5) mm.
Glumes

rounded to slightly keeled, keels scabrous towards the apices, lateral veins obscure to slightly prominent, not raised, apices acute to acuminate;

callus hairs 1.5-2(3) mm, 0.4-0.7 times as long as the lemmas, sparse;

lemmas 3-4.5 mm, 0.5-1.5(2) mm shorter than the glumes;

awns 3-4(4.5) mm, attached to the lower 1/10 – 3/10 of the lemmas, exserted, stout, easily distinguished from the callus hairs, strongly bent;

anthers 2-2.5 mm.
2n

= 56, 84-+104.

Calamagrostis porteri
Distribution
from FNA
AR; GA; IL; IN; KY; MD; MO; NC; NY; OH; PA; TN; VA; WV
[WildflowerSearch map]
[BONAP county map]
Discussion

Calamagrostis porteri grows in dry chestnut/oak forests, often on rocky ridgetops, piedmont bluffs, and slopes, at (100)600-1300 m. It is now restricted to the northeastern and central United States. Historically, its range extended from Missouri and Arkansas east to New York and Alabama. Flowering appears to be a response to disturbance; plants in undisturbed habitats remain vegetative and may go unnoticed. Thus the species may be more widespread and abundant than reported.

Calamagrostis porteri and C. rubescens (see next) appear to be closely related. They may be part of the general phenomenon of eastern and western vicariants. The apparently sterile C. perplexa (p. 726) is intermediate between C. porteri and C. canadensis (Greene 1980).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Leaf blades glaucous on both surfaces; leaf collars glabrous
subsp. insperata
1. Leaf blades light green and glaucous on the adaxial surfaces, darker green on the abaxial surfaces; leaf collars usually with prominent tufts of hair, rarely glabrous
subsp. porteri
Source FNA vol. 24, p. 721.
Parent taxa Poaceae > subfam. Pooideae > tribe Poeae > Calamagrostis
Sibling taxa
C. bolanderi, C. breweri, C. cainii, C. canadensis, C. cinnoides, C. deschampsioides, C. epigejos, C. foliosa, C. howellii, C. koelerioides, C. lapponica, C. montanensis, C. muiriana, C. nutkaensis, C. ophitidis, C. perplexa, C. pickeringii, C. purpurascens, C. rubescens, C. scopulorum, C. sesquiflora, C. stricta, C. tacomensis, C. tweedyi, C. ×acutiflora
Subordinate taxa
C. porteri subsp. insperata, C. porteri subsp. porteri
Name authority A. Gray
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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