Romulea rosea
Authors: Mandy Tu and Barry Rice, Global Invasive Species Team, The Nature Conservancy
Identifiers
Latin Names:
Romulea rosea (L.) Eckl.
Synonyms
Ixia rosea L.
Trichonema roseum Ker.
Common Names:
Guildford grass, onion grass, rosy sandcrocus
The genus name, Romulea, refers to Romulus, the legendary founder and first king of Rome. The species epithet, rosea, describes the rosy-coloration of the flower. The common names (onion grass and rosy sandcrocus) refer to its appearance.
Stewardship summary
Native to South Africa, Romulea rosea is an attractive herb in the Iris family (Iridaceae) that is often cultivated as an ornamental. Considered a weed in pastures and along roadsides in Australia, R. rosea was introduced into California (North America) by two sources; first by the import of its seed for horticulture, and then later as a contaminant in Trifolium subterraneum (subterranean clover) seed from Australia.[1] First detected in California from the Carmel Highlands, R. rosea is reported as having tripled its area between 1999 to 2000 along trails in the Elkhorn Slough (Monterey) area.[2] It has also been reported from the Point Reyes coastal region. Inland, R. rosea has only been reported from a single grassland site at approximately 500 ft elevation in Eldorado County.[1] Romulea rosea has the potential to spread along trails and walkways along the California coast, and potentially inland at low elevations. It does not however, seem to pose a large threat of invading undisturbed natural areas or significantly changing community structure.
Natural history
General
Romulea rosea (Iridaceae - Iris family) is a small herbaceous perennial with an underground, brown, rounded corm. It is generally less than 20 cm tall, and has simple grass-like leaves that are 5 to 35 cm long and 1 to 2.5 mm wide. Its solitary flowers have a funnel-shaped perianth that is 1.5 to 2 cm long, and is typically pink-violet/lilac in color on the perianth lobes and yellow on the perianth tube. Each flower is subtended by 2 bracts. The fruits are 10 to 15 mm in size, thin-walled, with persistent bracts. Seeds germinate in fall-winter, and flowering occurs in spring.[3]
The overall impacts of this new invader are unknown. However, it is difficult to remove R. rosea once an infestation has become established, due in part to its large reproductive capacity. The tough leathery leaf blades, furthermore, readily blunt mower blades, and grazing the plant by livestock in large quantities is not recommended as fiber balls may build-up internally within cattle.
Romulea rosea does not appear to significantly change community structure as it seems to only invade roadways and trails in California. In Australia, however, this species has invaded pasturelands, and can be easily transported into uninfested areas in the intestinal tracts of grazing animals.
Reproduction
Romulea rosea can reproduce both vegetatively (by cormlets) and by seed. The seeds may be eaten by livestock and transported to uninfested areas.[4] Soil disturbance and water may also transport seeds and corms small distances.[5]
Range
Romulea rosea is native to the western cape region of South Africa.[6] As an invader, R. rosea may become problematic in northern California along the coast, and inland as far as Eldorado County. In Australia, R. rosea is widespread in Tasmania, and is most commonly found in disturbed/run-down areas, in pastures and turf areas such as sports fields, and on roadsides.[7][8][9]
Management/Monitoring
Little information is available on the control of R. rosea. Most of the control suggestions below are extrapolations of methods shown to be effective on other small corm-forming lilies.
1) Small populations of R. rosea can be dug or hand-pulled out. If hand-pulling, be careful to remove the entire corm and any cormlets. Cormlets left behind can resprout. Pulling and digging efforts must be continued for several years to ensure that remaining seeds and cormlets have been removed.[9] In non-wildland areas, regular cultivation or cropping-cycles can eventually kill R. rosea populations.
2) Control of larger infestations can be achieved by spraying with the herbicide glyphosate (RoundUp) when R. rosea is in full flower or just about to set seed. Glyphosate will, however, kill all other grasses and forbs, except possibly white clover.[7]
3) Animals (cattle or sheep) can graze upon R. rosea. However, large amounts of R. rosea ingestion in cattle can lead to the formation of phytobezoars (fiber balls) in the gut, and can cause acute intestinal obstruction.[10] Leaves of R. rosea may be unpalatable to sheep and cattle at certain times of the year [4], and fungal pathogens on its leaves may be deleterious to sheep.[11] Mowing is not effective in controlling this species.[7]
Information sources
Bibliography
- ↑ Hrusa, G.F. 2000. California Department of Food & Agriculture, personal communication. 1.0 1.1
- ↑ Otter, N. 2000. Elkhorn Slough National Estuarine Preserve, personal communication.
- ↑ Hickman, J.C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press, Berkeley.
- ↑ Eddy, J.L. 1973. Onion-grass in pasture. Weed Science Society of Victoria: Proceedings of the Second Victorian Weeds Conference, Parkville, Victoria, March 26-27, 1973. pp.4-17 - 4-21. 4.0 4.1
- ↑ Eddy, J.L. and D.F. Smith. 1975. Seed dispersal and germination in Romulea rosea (onion grass). Australian Journal of Experimental Agriculture and Animal Husbandry 15: 508-512.
- ↑ TROPICOS. 2001. Missouri Botanical Garden's VAST nomenclatural database. (http://www.tropicos.org).
- ↑ Smith, R.S. 1978. Onion grass. Tasmanian Journal of Agriculture 49(4): 212-214. 7.0 7.1 7.2
- ↑ Scott, J.K. and E.S. Delfosse. 1992. Southern African plants naturalized in Australia: a review of weed status and biological control potential. Plant Protection Quarterly 7(2): 70-80.
- ↑ Ewart, A.J. 1907. Guildford grass, or onion grass. The Journal of the Department of Agriculture of Victoria 5: 537-540. 9.0 9.1
- ↑ Pitt, J.N. 1976. Phytobezoars in cattle. Victorian Veterinary Proceedings 34: 27-28.
- ↑ Leach, C.M. and M. Tulloch. 1972. World-wide occurrence of the suspected mycotoxin producing fungus Drechslera biseptata with grass seed. Mycologia 64(4): 1357-1359.
Source Document
Weed Alert: Romulea rosea; Mandy Tu and Barry Rice, 2001.
