**Polypogon interruptus HBK. (Poaceae)**

**Ditch Polypogon, Ditch Beard Grass**

**Description**. Tufted perennials, sometimes flowering the first year,
stems 1-8 dm tall, erect, often bent at the base, rooting at the lower
nodes, glabrous to minutely scabrous. Leaves alternate; ligules 3-10 mm
long, clearly veined, apices obtuse to truncate, slightly erose;
auricles absent; sheaths glabrous to minutely scabrous; blades linear,
flat, 2-10 mm wide, scabrous. Inflorescence 3 to 10 cm long, a terminal,
interrupted panicle composed of of several densely clustered spikes.
Spikelets composed of 1 floret, the glumes 1.5-3 mm long, subequal,
1-nerved, keeled, puberulent, the apices acute, abruptly short- awned,
sometimes minutely bilobed, awns 1 -3 mm long; lemma 1-1.5 mm long,
narrowly lanceolate, smooth, shiny, often transparent, the apex minutely
toothed or awned, the awn up to 2 mm long. In California, flowering from
May to September. (Arnow 1987, Clapham et al. 1962, Conley 1993,
Hitchcock 1944, Holmgren and Holmgren 1977, Munz 1959, Sutherland 1986,
Tutin 1980).

The related annual, *P. monspeliensis*, rabbitfoot grass, has glumes
with apices that are bilobed, obtuse, and with awns 3-10 mm long.

**Geographic Distribution**. A native of South America, ditch Polypogon
has become widely naturalized in western North America, and has been
reported as a waif east of the Rocky Mountains. It apparently has not
been introduced elsewhere. The related *P. monspeliensis* is native to
Great Britain and Europe, and has become naturalized throughout much of
temperate North America, Australia, Japan, southern Africa and Hawaii
(Chapman 1991, Clapham et al. 1982, Fernald 1950, Gibbs Russell et al.
1955, Gleason and Cronquist 1991, Holmgren and Holmgren 1977, Koyama
1987, Montenegro et al. 1991, Sutherland 1986, Munz 1959, Tselev 1984,
Tutin 1980, Wagner et al. 1990).

*Polypogon interruptus* was first reported (probably as *P. lutosus* and
*P. littoralis*) as widespread, presumably by the mid 19th century, by
Watson (1880). *Polypogon monspeliensis* was first reported from
California (San Francisco) by Bolander (1870). It had become widespread
before the end of the 19th century, especially in rice fields of
northcentral California (Robbins 1940).

*Polypogon interruptus* occurs on Santa Cruz, Santa Rosa and San Miguel
islands (Junak et al. 1997) and is distributed throughout California
(Anonymous 1998, Conley 1993, Munz 1959). *Polypogon monspeliensis* is
known from all the northern California Channel Islands (Junak et al.

1997).

**Reproductive and vegetative biology**. Like most species of grasses,
*Polypogon* is probably wind-pollinated; close relatives in *Agrostis*
are mainly self-pollinated (Proctor et al. 1996). No literature was
found that discussed aspects of its reproductive biology. Mamood et al.
(1996) reported decreasing levels of seed germination of *Polypogon
monspeliensis* with increasing salinity. Inderjit and Dakshini (1995)
reported allelopathic effects by *Polypogon* straw on cultivated crops
in India.

**Ecological distribution**. Both *Polypogon interruptus* and *P.
monspeliensis* are found in moist sites along streams, ditches,
irrigation canals, waste areas, and abandoned fields (Conley 1993,

Munz 1959, Robbins et al. 1970, Stromberg 1995). Kuhn and Zedler (1997)
documented invasion of southern California coastal marshes by *Polypogon
monspeliensis* resulting from the influx of

fresh water. In the Nile Delta, *Polypogon monspeliensis* has invaded
similar areas formerly

occupied by native chenopods (el-Din 1993). It also has become an
important element in Sonoran Desert riparian ecosytems (Stromberg 1995).

**Weed status**. No species of *Polypogon* are considered noxious weeds
in agricultural or horticultural practice, at least at a global level
(not listed by Holm et al. 1977), nor are

they considered noxious by the State Dept. of Food and Agriculture
(Anonymous 1996). They are not listed for the United States in Lorenzi
and Jeffery (1987).

**Microbial pathogens**. *Polypogon monspeliensis* is known to be a host
of the rust fungus*, Puccinia polypogonis* (Baka and Gjaerum 1996). In
Australia, *Polypogon monspeliensis* is host to a bacterium,
*Clavibacter toxicus*, which causes a disease in cattle after ingesting

infected spikelets. (Bertozzi and McKay 1995, McKay et al. 1993). Both
*P. interruptus* and *P*. *monspeliensis* can be hosts to mycorrhizal
fungi (Lugo et al. 1997).

**Insect pathogens**. No literature was found that reported *Polypogon*
species as hosts of deleterious insects.

**Herbicide control**. No literature was found that reported herbicide
control of any *Polypogon* species.

**Literature Cited**

Anonymous. 1996. Exotic pest plants of greatest ecological concern in
California as of August 1996. California Exotic Pest Plant Council. 8
pp.

Anonymous. 1998. USDA Plants Database, Baton Rouge, LA. URL
usda.plants.gov.

Baka, Z. and H. Gjaerum. 1996. Egyptian Uredinales: I. Rusts on wild
plants on the Nile Delta. Mycotaxon. 60: 291-303.

Bertozzi, T. and A. McKay. 1995. Incidence on *Polypogon monspeliensis*
of *Clavibacter toxicus* and *Anguina* sp., the organisms associated
with "flood plain staggers" in South Australia. Australian Journal of
Experimental Agriculture. 35: 567-569.

Bolander, H. 1870. A catalog of plants growing in the vicinity of San
Francisco. A. Roman and Co., San Francisco, California. 43 pp.

Clapham, A., T. Tutin, and E. Warburg. 1962. Flora of the British Isles.
Cambridge University Press, Cambridge. 1269 pp.

Conley, S. 1993. *Polypogon*. In Hickman, J. (ed.). The Jepson manual:
Vascular plants of California. University of California Press, Berkeley.
1400 pp.

el-Din, A., H. el-Kady, and Y. Sodany. 1993. Gradient analysis of the
common species in the saline and marshy habitats in the Nile Delta.
Feddes Repertorium. 104: 387-394.

Gibbs Russell, G., L. Watson, M. Koekemore, L. Smook, N. Barker, H.
Anderson, and M. Dallwitz. 1955. Grasses of southern Africa. Memoirs of
the Botanical Survey of South Africa. No.58. 437 pp.

Hitchcock, A. 1944. Poaceae. pp.103-255. In Abrams, L. Illustrated flora
of the Pacific States. 1. Ophioglossaceae to Aristolochiaceae, Stanford
University Press, Stanford, California. 538 pp.

Inderjit and K. Dakshini. 1995. Allelopathic potential of an annual
weed, *Polypogon* *monspeliensis*, in crops in India. Plant and Soil.
173: 251-257.

Koyama, T. 1987. Grasses of Japan and its neighboring regions. Kodansha,
Tokyo, Japan. 570 pp.

Kuhn, N. and J. Zedler. 1997. Differential effects of salinity and soil
saturation on native and exotic plants of a coastal salt marsh.
Estuaries. 20:391-403.

Lugo, M., L. De Toledo, and A. Anton. 1997. Six species of Glomales
(Zygomycetes) in Argentine Poaceae. Kurtziana. 25:187-204.

Mahmood, K., K. Malik, M. Lodhi, and K. Sheikh. 1996. Seed germination
and salinity tolerance in plant species growing on saline wastelands.
Biologia Plantarum. 38:309-

315\.

Mckay, A., K. Ophel, T. Reardon, and J. Gooden. 1993. Livestock deaths
associated with *Clavibacter toxicus* -*Anguina* infection in seedheads
of *Agrostis avenacea* and *Polypogon monspeliensis*. Plant Disease.77:
635-641.

Montenegro, C., S. Teillier, P. Arce, and V. Poblete. 1991. Introduction
of plants into the mediterranean-type climate area of Chile. pp.
103-114. In Groves, R. and F. Di Castri. Biogeography of Mediterranean
invasions. Cambridge University Press, Cambridge. 485 pp.

Munz, P.1959. A flora of California. University of California Press,
Berkeley. 1691 pp.

Robbins, W. 1940. Alien plants growing without cultivation in
California. Agricultural Experiment Station. Bulletin 637. University of
California, Berkeley. 128 pp.

Stromberg, J. 1995. Exotic herbaceous species in Arizona\'s riparian
ecosystems. pp.45-57. In Brock, J. et al. (eds.). Plant invasions:
Studies from North America and Europe.

Backhuys Publishers: Leiden, The Netherlands. 223 pp.

Sutherland, D. 1986. Poaceae. pp. 1113-1235. In Great Plains Flora
Association. 1986. Flora of the Great Plains. University of Kansas,
Lawrence. 1392 pp.

Tselev, N. 1984. Grasses of the Soviet Union. Part 1. Balkema,
Rotterdam, The Netherlands. pp.1-568.

Wagner, W., D. Herbst, and S. Sohmer. 1990. Manual of the flowering
plants of Hawaii. 1853 pp.

Watson, S. 1880. Geological Survey of California. Botany. Volume 2. John
Wilson, University Press, Cambridge, Massachusetts. 622 pp.