Plant Species of the Bright Angel Trail:
slender wheatgrass, Elymus trachycaulus

See Plant Guide to Bright Angel Trail for an introduction to this page, especially the Introduction To These Species Pages.


Identification status: 100%. Even better, there appears to be no other similar grass at the Grand Canyon, at least as given in McDougall.

Keying using McDougall:

1'  Spikelets one at each node
2'  Spikelets breaking above glumes
19  Spikelets sessile
20  Spikelets borne on opposite sides of the inflorescence
21  Spikelets 1 per node
22' First glume present; flat side of spikelet facing stem
23' Glumes 5 veined; plants perennial
24  Plants without rhizomes, bunchgrasses  ... Agropyron trachycaulum

The McDougall description fits, except I'd call the glumes acute-tipped, not "awn-pointed".

Here is a description of a dried culm from a plant growing along a sidewalk at the Bright Angel Lodge.

Stem: 3.9 dm, including infl

Leaves: just two cauline, ascending at an angle of just 15-20 degrees from vertical, uppermost 5 cm x ≤~1.0 mm, rolled except at very base. Sheath open to base, a distance of 11 cm. Upper part of sheath is squared off, but there is no auricle. Ligule appears almost non-existent, just ~0.1 mm, membranous, truncate.

Inflorescence: 10 cm spike, with 10 appressed spikelets, 1 per node, flat side facing stem, internodes 7-8 mm.

Spikelets 15-17 mm, florets 4-6, stalks ~2 mm between florets

Lower glume 6.8 mm, 5 veined
Upper glume 7.1 mm, 5 veined

Lemma 9.7 mm, veins 5, converging, tip sharp-point of ~0.4 mm, body scabrous or very short hairy all over back

Palea 8.2 mm

The above characteristics fit the Jepson Manual description perfectly except that the lemma awn is only 0.4 mm, not 1-30 mm. The Utah Flora says acute to awn-tipped or with an awn 2-20(30) mm long. The Arizona plants must be mostly awnless, since McDougall just says the lemmas of the Grand Canyon plants are awn-pointed, and the SEINet description says glumes and lemmas awnless.

From a SEINet search on 31 August 2008, there are 26 vouchers of this species from the Coconino County portion of the Grand Canyon. The nearest are at: Railroad Track; and South rim of Grand Canyon. Note that there may be additional vouchers at other herbaria not available through SEINet.

This species seems vastly undercollected in the Grand Canyon in the Village Area and on the trails. Nearly all of the online vouchers are from the North Rim.

First occurrence on Bright Angel Trail: mile 0.28, elevation 6695 feet (2041 m).

Number of plants along Trail: at least 50 plants were found in at least 9 different locations in September 2007.


From 6 September 2007, mile ~0.60 (I forgot to take pictures of the first specimens on the trail), specimens that have lost most or all of their lemmas:

From 6 September 2007, mile ~0.70, of a specimen that still has some of the lemmas attached:

From 25 August 2008, from a specimen growing along the sidewalk at the Bright Angel Lodge:

In the following picture, both sides are shown of the glumes and lemmas. The light direction is from the right, to enhance the visibility of the veins. On the left, the palea is seen filling the body of the lemma, with the styles sticking out of the palea in the upper middle.


Online pictures:

SEINet voucher

USDA Plants picture by Robert Soreng.

Calphotos: Elymus trachycaulus and ssp. trachycaulus.

See Resources for Grand Canyon Flora for further information on most of these references. Entries in the second column are either the name used in that source or a page reference. The name is linked to online pages when available. If a given reference does not contain this taxon, the entry is either left blank or contains a hyphen.

Scientific NameElymus trachycaulus
1987 Grand Canyon Flora NameAgropyron trachycaulum
1987 Grand Canyon Flora page14
SEINet Image PageElymus trachycaulus
USDA PlantsElymus trachycaulus
Flora of North America
Jepson Manual for California treatmentElymus trachycaulus
Jepson Manual illustration page1261
Kearney and Peebles NameAgropyron trachycaulum
Kearney and Peebles Page #93
Vascular Plants of AZ name
Vascular Plants of AZ volume: page
Huisinga et al 2006 name-
Huisinga et al 2006 page numbers-
Epple Name-
Epple description page #-
Epple pix #-
McDougall 1964 nameAgropyron trachycaulum
McDougall 1964 page #46
Brian 2000 Name
Phillips 1979 name-
Phillips 1979 page #-
Stockert 1967 name-
Stockert 1967 page #-

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Copyright © 2007-2008 by Tom Chester.
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
Comments and feedback: Tom Chester
Last Update: 31 August 2008