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Tribolium obliterum (Hemsl.) Renvoize
(cape grass)

Summary: new plant of unknown characters
Tribolium obliterum (Hemsl.) Renvoize is a non-native grass believed to have arrived in California as an ornamental. The Plant Diagnostics Center of the California Department of Food and Agriculture has given the plant a Q rating, meaning that it is a quarantine plant and will be intercepted if sold in the U.S. until further evaluation. The quarantine rating is primarily because the behavior of the plant is unknown at this time (1). The identification of T. obliterum from Fort Ord, near Monterey is a first for California and for North America. Although its impact on wild lands is unknown, it has been found to be spreading in the Fort Ord area.

Patches now occur in a 3 by 1.5 km area of maritime chaparral that has signs of disturbance from army use. Tribolium obliterum may grow by itself, or hidden among other plants making it difficult to detect (2).

(Click on thumbnail images for a closer view)

Tall plants

Short plants



Herbarium images
(Top four photographs compliments Susan Hubbard)

Tribolium obliterum (Hemsl.) Renvoize is a perennial grass (Poaceae). It has decumbent or erect culms 12-40 cm long, with 3-4 nodes (3). The leaf blades are linear and narrow, 0.5-1 mm wide and 1-8 cm long (3), without cross venation. Plants in the genus Tribolium are bisexual with bisexual spikelets and hermaphrodite florets (4). It its native range, flowering occurs in the spring (September - November) (6). The fruit (caryopsis) is small, 1-2 mm in length, yellow-brown in color, obovate, and compressed dorsiventrally (4). In California, stolons were observed on some plants during the winter, but did not appear to be rooting or producing new plants (2).

Scientific and Common Names:
The genus name, Tribolium, was derived from the Latin tri, meaning three and bolus, meaning a fiery meteor in the form of an arrow. The genus name was possibly in reference to the bristly glumes surrounding the 3 florets (2). Synonyms for Tribolium obliterum are numerous including "Brizopyrum glomeratum" and "Poa glomerata". See the Missouri Botanical Gardens website (5) for a complete list. The common name "cape grass" was coined by Hrusa (1).

The impacts of this new invader are not yet known. In disturbed sites the impact of T. obliterum is minimal, but it may compete with native bunchgrasses where they grow together (2). Other species in the genus Tribolium can be agricultural weeds, but are not considered invasive in natural areas (1).

Native Range:
Tribolium obliterum is native to South Africa. The genus contains ten species that occur in the Fynbos and Karoo and commonly are adventive (4). Tribolium obliterum is typically found at low altitudes on gravelly, well-drained soils (3).

Range As An Invader:
Tribolium obliterum is an invader in one small site in California (USA), and at sites in Australia, and on St. Helena and Ascension Islands in the Atlantic. There are no reports of it spreading rapidly in these areas (3). The California Tribolium obliterum population is spreading in an eroded gully and in a restoration site where the soil was disturbed. Species in the genus Tribolium are mesophytic to xerophytic, common in open habitats, and do not like salty soils (4). Susan Hubbard (2) has observed that T. obliterum prefers clear, flat areas and has been found along dirt roads and in other disturbed areas. Seeds may be spread by water. In Fort Ord, plants have been found in water channels and places where water is expected to run.

Reproduction and Methods of Dispersal:
Seeds may be spread by water. In Fort Ord, plants have been found in water channels and places where water is expected to run. Although stolons were observed, they did not appear to be rooting or producing new plants. It is still unknown whether T. obliterum can spread by vegetative growth (2).

1)Digging the plant up with a shovel has been effective.
2)Glyphosate (Roundup) appears to be effective (although non-selective) against T. obliterum. Applications made with 2% glyphosate appear to be successful. In the future follow-up applications may be necessary.
3)The infestation at Fort Ord in California appears to be associated with disturbed areas. Minimizing disturbance to natural areas may help prevent establishment.

1)Hrusa, G.F. 2001. Senior Plant Systematist in the Herbarium of the Plant Pest Diagnostics Center, California Department of Food and Agriculture. Personal communication.
2)Hubbard, S. 2001. Bureau of Land Management at Fort Ord. Personal communication.
3)Linder, H.P. and G. Davidse. 1997. The systematics of Tribolium Desv. (Danthonieae: Poaceae)
4)Watson, L. and M.J. Dallwitz. 1992 onwards. Grass Genera of the World: Descriptions, Illustrations, Identification, and Information Retrieval; including Synonyms, Morphology, Anatomy, Physiology, Phytochemistry, Cytology, Classification, Pathogens, World and Local Distribution, and References. (http://biodiversity.uno.edu/delta/grass/www/triboliu.htm) Version: 18th August 1999.

--Tunyalee Martin/Wildland Invasive Species Team; April 2001

Updated January 2005
©The Nature Conservancy, 2001