Phytoneuron

Malusa, J., K. Reichhardt, R.S. Felger. 2013. Giant sandbur ( Cenchrus palmer, Poaceae) new for Arizona and the United
States. Phytoneuron 2013-91: 1-5. Published 22 November 2013. ISSN 2153 733X

GIANT SANDBUR (CENCHRUS PALMERIT, POACEAE)
NEW FOR ARIZONA AND THE UNITED STATES

JIM MALUSA*
School of Natural Resources and the Environment
University of Arizona
Tucson, Arizona 85721
malusa@email.arizona. edu
*author for correspondence

KAREN REICHHARDT
Bureau of Land Management
Yuma County, Arizona
kreichha@blm.gov

RICHARD STEPHEN FELGER
Herbarium, University of Arizona
Tucson, Arizona 85721
rfelger@ag. arizona.edu

ABSTRACT
Cenchrus palmeri from Yuma County, Arizona, is documented as new for the flora of the
USA. It is one five of species of grasses endemic to the Sonoran Desert.

KEY WORDS: Cenchrus palmeri, Marine Corps Air Station, Yuma County, Arizona, first USA record,
Poaceae

Cenchrus palmeri Vasey has not previously been recorded as a member of the USA flora.
Felger (2000) suggested that it should be sought in natural areas on sandy soils in the southwestern
Arizona border region along the southern border in Cabeza Prieta National Wildlife Reserve and the
Tinajas Altas region. On 5 January 2013, Jim Malusa and Abigail Rosenberg found a single specimen
between the Tinajas Altas Mountains and the Yuma dunes, about five miles north of the international
border (Fig. 1). It was photographed (Fig. 2) but not collected. Two weeks later, a population of
500-1000 plants was discovered by Malusa and Pete Sundt at a location about 1.5 miles further
northeast and about 6 miles from the international border; the collections below were made from this
locale (Figs. 3-5). In July of 2013, from the same location, Karen Reichhardt identified specimens
found by Del Maslen, a range warden for Marine Corps Air Station, Yuma. We predict that C.
palmeri will expand its range in southwestern Arizona during years with favorable rains, such as the
summer rains of 2013.

Vouchers. USA. Arizona. Yuma Co.: Barry M. Goldwater Range, Marine Corps Air Station-
Yuma, Hazard Area 4 (Figure 1):

(1) ca. 3 mi NW of the target known as Yodaville (Quad: West of Vopoki Ridge), and 12 mi 8 of Foothills
community in Yuma, Arizona; UTM Zone 11, WGS 84, 7 46 608 E, 35 94 308 N, WGS 1984, 130 m;
along roadside at observation tower, and in nearby runnels; sandy flats, associated species: Larrea
tridentata, Palafoxia arida, Dalea mollis, Brassica tournefortii, population estimated at 500-1000 plants,
19 Jan 2013, J. Malusa & P. Sundt s.n.2 sheets, ARIZ 413972 & 413973).

(2) ca. 3 mi NW of the target known as Yodaville (Quad: West of Vopoki Ridge), and 12 mi 8 of Foothills
community in Yuma, Arizona; near observation tower behind a fence with evidence that illegal aliens on
foot from Mexico hide and stage; tower is reached via paved road; sandy soil, relatively flat mesa terrain
with Larrea tridentata, UTM Zone 11, WGS 84, 7 46 604 E, 35 94 317 N, +- 11ft, with Garmin GPS 60

Malusa, Reichhardt, and Felger: Cenchrus pa/meri new to Arizona and the USA 2

CSX, 11 July 2013, D. Maslen s.n. (Bureau of Land Management Yuma Field Office Herbarium, and
ARIZ 415466).

(3) 11 mi S of Foothills area of Yuma, Arizona on MCAS- Yuma Barry M. Goldwater Range; found
growing on both sides of the road 1 mi N of first USA collection locality (Malusa & Sundt, 19 Jan 2013);
sandy soil; UTM Zone 11, WGS 84 118 07 45 790 E, 35 95 957 N, 4 Sep 2013, D. Maslen s.n. (Bureau
of Land Management Yuma Field Office Herbarium, and ARIZ 415467).

m Bike

Figure 1. Location of Cenchrus palmeri in Arizona.

Cenchrus palmeri is a non-seasonal annual (ephemeral) growing and reproductive with ample
rains, and perishing with winter freezing. It is highly variable in size, often (5) 8-30 cm long, with
small, weakly developed roots. The burs, 1—3 per inflorescence, with a body 20-31 mm in diameter,
have sharp, rigid spines (6) 9-15 mm long. The burs, the largest of any species of Cenchrus, persist
long after the plant dies, often half hidden in the sand. (Figs. 2-5).

This unique grass occurs on sandy or silty soils as well as rocky slopes. Gould and Moran
(1981: 123) pointed out that “This readily recognizable sandbur is one of the most distinct of the
genus and is one of the very few grasses endemic to the Sonoran Desert.” However, it also ranges
somewhat south of the desert along the coast to northwestern Sinaloa (Felger 2000). It is known from
both states of Baja California, most islands in the Gulf of California, western Sonora northward to the
Pinacate Region near the United States border, and the Gran Desierto dune fields of northwestern
Sonora, close to the Arizona border in Yuma County. This species joins four others as the only
grasses endemic or nearly endemic to the Sonoran Desert: Aristida californica Thurber var.
californica, Distichlis palmeri (Vasey) Fassett, Muhlenbergia brandegei C. Reeder, and Tuctoria
fragilis (Swallen) Reeder (Felger 2000; Felger & Wilder 2012; Peterson & Annable 1991; Reeder
1982; Reeder & Felger 1989).

No other species of Cenchrus sensu stricto has so small a geographic range, such large burs,
or so few burs per inflorescence (DeLisle 1963). As with some other Cenchrus species, seedlings
germinate within the bur, which may remain attached to the root of the mature plant. Cenchrus
palmeri burs not only puncture sleeping bags, tents, and bare feet at the beach but they tenaciously
cling together in nasty clusters attaching to cloths and shoes. Border crossers from Sonora to Arizona

Malusa, Reichhardt, and Felger: Cenchrus pa/meri new to Arizona and the USA 3

are likely vectors. Crossing at night, they often attach piece of carpet to their shoes and Cenchrus
burs might well cling to the carpet pieces and fabric shoes. Similarly, the burs are also transported by
vehicle tires (Fig. 3), as was the case at the Arizona collection site.

Figure 2. Cenchrus palmeri, the sole specimen at the site near the Yuma Dunes, not collected.
Photo by J. Malusa, 5 January 2013.

Figure 3. Cenchrus palmeri bur, at the collection site. Photo by J. Malusa, 19 January 2013.

Malusa, Reichhardt, and Felger: Cenchrus palmeri new to Arizona and the USA 4

usa, 19 January 2013.

Figure 4. Cenchrus palmeri at the collection site. Photo by J. Mal

Figure 5. Cenchrus palmeri, from the collection site. Photo by J. Malusa, 19 January 2013.

Malusa, Reichhardt, and Felger: Cenchrus palmer/ new to Arizona and the USA 4

ACKNOWLEDGEMENTS
Thanks to Laura Crumbacher and George Ferguson at ARIZ, Del Maslen, U.S. Conservation
Law Enforcement Officer at the Marine Corps Air Station- Yuma, Abigail Rosenberg, Natural
Resource Specialist, MCAS-Yuma, and Pete Sundt.

LITERATURE CITED
DeLisle, D.G. 1963. Taxonomy and distribution of the genus Cenchrus. Iowa State J. Sci. 37: 259-

Felger, R.S. 2000. Flora of the Gran Desierto and Rio Colorado of Northwestern Mexico. Univ. of
Arizona Press, Tucson.

Felger R.S. and B.T. Wilder with H. Romero-Morales. 2012. Plant Life of a Desert Archipelago:
Flora of the Sonoran Islands in the Gulf of California. Univ. of Arizona Press, Tucson.

Gould, F.W. and R. Moran. 1981. The Grasses of Baja California, Mexico. Mem. San Diego Soc.
Nat. Hist. 12: 1-140.

Peterson, PM. & C.R. Annable. 1991. Systematics of the annual species of Muhlenbergia (Poaceae-
Eragrostideae). Syst. Bot. Monogr. 31: 1-109.

Reeder, J.R. 1982. Systematics of the tribe Orcuttieae (Gramineae) and the description of a new
segregate genus, Tuctoria. Amer. J. Bot. 69: 1082-1095.

Reeder, J.R. and RS. Felger. 1989. The Aristida californica-glabrata complex (Gramineae).
Madrofio 36: 187-197.