TECHNICAL KEY TO COMMON GRASS GENERA
Copyright 2002, A.F. Cholewa, J.F. Bell Museum of Natural
History, University of Minnesota / No portion of this guide may be duplicated
without written permission of author.
To use this identification key you will need a good hand lens or magnifying
glass and the plants must be in flower/fruiting stage. The key is arranged in
such a way that you always have two choices, a or b, with subsequent choices
dependent upon the prior choice. Successful navigation requires that you
consider both a and b for each number before making the choice. If neither
a nor b seems appropriate, backup to the previous number and re-examine
the choices. The number of species in the state for that genus is
listed
in parentheses. Refer to the introduction ("The grass plant") for help with
structural terms. Feedback is appreciated; please send a separate email
message to chole001@umn.edu
1a. Spikelets all unisexual (carpellate spikelets in upper part of
inflorescence, staminate in lower) ----------------------------------------------
ZIZANIA
1b. Spikelets with at least 1 perfect floret (anthers may be lost
after maturity but spikelets look similar throughout
inflorescence) -------------------------------------------------------------------- # 2
2a. Plants at least 1.5 m tall at maturity ---------------------------------------
PHRAGMITES
2b. Plants under 1.5 m tall ---------------------------------------------------- # 3
3a. Spikelets covered with spines ---------------------------------------------
CENCHRUS
3b. Spikelets not spiny -------------------------------------------------------- # 4
4a. Glumes absent ------------------------------------------------------------------
LEERSIA
4b. At least 1 glume present, though sometimes minute ----------- # 5
5a. Spikelets with only 1 fertile floret ------------------------------------- # 6
5b. Spikelets with 2 or more fertile florets ------------------------------ # 28
6a. Spikelets with 1 or more sterile florets present (spikelets
therefore with at least 2 florets) -------------------------------------------- # 7
6b. Spikelets with just 1 floret ---------------------------------------------- # 16
7a. Spikelets paired at each node, usually one is sessile/subsessile
and one pediceled; the pediceled spikelet staminate, neuter, or
epresented by a pedicel only ---------------------------------------------- # 8
7b. Spikelets not paired or if paired not as in 7a -------------------- # 10
8a. Spikelets arranged in a panicle; pedicellate spikelet
represented by pedicel only -----------------------------------------------------
SORGHASTRUM
8b. Spikelets arranged in a raceme; pedicellate spikelet
present --------------------------------------------------------------------------- # 9
9a. Branches of inflorescence terminating in a single
spike-like raceme ------------------------------------------------------------------
SCHIZACHYRIUM
9b. Branches of inflorescence terminating in a cluster of
spike-like racemes ----------------------------------------------------------------
ANDROPOGON
10a. Sterile florets present above the fertile floret -----------------------
BOUTELOUA
10b. Sterile florets present below the fertile floret ------------------ # 11
11a. Sterile floret 1; second glume similar to sterile lemma ----- # 12
11b. Sterile florets 2; second glume not similar to
sterile lemma ------------------------------------------------------------------ #
15
12a. Spikelets subtended by long bristles ---------------------------------
SETARIA
12b. Bristles lacking --------------------------------------------------------- # 13
13a. Fertile lemma hardened at maturity, margins generally
inrolled over palea ----------------------------------------------------------- # 14
13b. Fertile lemma thin, margins not inrolled over palea --------------
DIGITARIA
14a. Spikelet awned; second glume and sterile lemma with stiff
hairs over the back; tip of fertile palea enclosed by the fertile
lemma --------------------------------------------------------------------------------
ECHINOCHLOA
14b. Spikelets awnless and hairless; tip of fertile palea generally
visible --------------------------------------------------------------------------------
PANICUM
15a. Sterile florets staminate -------------------------------------------------
HIEROCHLOE
15b. Sterile florets represented by hairy scales -------------------------
PHALARIS
16a. Awns lacking ----------------------------------------------------------- # 17
16b. Awns present on either glumes or lemmas (look carefully
as these may break off in old material) ------------------------------- # 20
17a. Glumes as long as or longer than the lemma ----------------- # 18
17b. At least the first glume shorter than the lemma --------------- # 19
18a. Callus long-hairy; palea present --------------------------------------
CALAMAGROSTIS
18b. Callus not long-hairy; palea absent or poorly developed ------
AGROSTIS
19a. Lemma 3-nerved ----------------------------------------------------------
MUHLENBERGIA
19b. Lemma 1-nerved ----------------------------------------------------------
SPOROBOLUS
20a. Spikelets all turned to one side and crowded --------------------
SPARTINA
20b. Spikelets not as above --------------------------------------------- # 21
21a. Disarticulation below the spikelet (so that after fruits
have shed only the main stalk of the inflorescence
remains) ----------------------------------------------------------------------------
ALOPECURUS
21b. Disarticulation above the glumes (at least some glumes
remain on the inflorescence after fruit have
dropped) ----------------------------------------------------------------------- # 22
22a. Lemma hardened, awned ----------------------------------------- # 23
22b. Lemma not hardened, awned or awnless -------------------- # 25
23a. Awn 3-branched ---------------------------------------------------------- ARISTIDA
23b. Awn unbranched ----------------------------------------------------- # 24
24a. Awn straight or curved but not twisted or coiled ----------------
ORYZOPSIS
24b. Awn twisted or coiled several times at least near base ------
STIPA
25a. Glumes equal in size and shape, apex broad and
abruptly short-awned -----------------------------------------------------------
PHLEUM
25a. Glumes unequal or apex narrow or tapering ---------------- # 26
26a. Lemma awned from the back or from near base;
glumes equaling or longer than the lemma ------------------------- # 27
26b. Lemma awned from apex; at least the 1st glume
shorter than the lemma --------------------------------------------------------
MUHLENBERGIA
27a. Callus long-hairy; palea present, appearing as a
translucent stiffer hair; rachilla present -----------------------------------
CALAMAGROSTIS
27b. Callus not long-hairy; palea absent or poorly
developed; rachilla absent ---------------------------------------------------
AGROSTIS
28a. Inflorescence a spike (1 or more spikelets per node) ---- # 29
28b. Inflorescence a panicle -------------------------------------------- # 32
29a. Spikelets all solitary at nodes of the inflorescence -------- # 30
29b. Spikelets 2 or more per node ----------------------------------- # 31
30a. Plants bunchgrasses ---------------------------------------------------
EYMUS (E.
trachycaulus)
30b. Plants rhizomatous ------------------------------------------------------
ELYTRIGIA
31a. Spikelets 3 at each node; the laterals reduced and
pedicellate ------------------------------------------------------------------------
HORDEUM
31b. Spikelets 2-4 per node; all fertile ------------------------------------
ELYMUS
32a. Lemmas awned ----------------------------------------------------- # 33
32b. Lemmas awnless --------------------------------------------------- # 36
33a. First glume 3 or 5-nerved ---------------------------------------- # 34
33b. First glume 1 or 3-nerved ---------------------------------------- # 35
34a. Callus long hairy; leaf sheaths open ------------------------------
SCHIZACHNE
34b. Callus not hairy; leaf sheaths closed -----------------------------
BROMUS
35a. Lemma apex bifid (sometimes the apex is minutely
bifid with the awn appearing to be attached just below
the apex); spikelets over 1.5 cm long -----------------------------------
BROMUS
35b. Lemma apex acute or minutely bifid; spikelets
under 1.2 cm long ------------------------------------------------------------
FESTUCA
36a. Nerves of lemma parallel ---------------------------------------- # 37
36a. Nerves of lemma curving towards apex, not parallel ---- # 38
37a. Lemmas 3-nerved; plants under 3 dm tall ----------------------
ERAGROSTIS
37b. Lemmas 5-nerved; plants over 3 dam tall ----------------------
GLYCERIA
38a. Lemmas 5-nerved ------------------------------------------------ # 39
38b. Lemmas 7-nerved ----------------------------------------------------
BROMUS
39a. Lemma apex acute to acuminate, rounded on the
back ------------------------------------------------------------------------- # 40
39b. Lemma apex obtuse to acute, keeled on the back ----------
POA
40a. Glumes as long as the lemmas; spikelets mostly
2-flowered ----------------------------------------------------------------------
KOELERIA
40b. Glumes clearly shorter than the lemmas; spikelets
several flowered --------------------------------------------------------------
FESTUCA