| SOURCE:
The following information on this species is taken from The Nature Conservancy,
Invasive Species Initiative, Element Stewardship Abstract (ESA) for Conium
maculatum at http://tncweeds.ucdavis.edu/esadocs/conimacu.html.
Modifications include additional resource information. Check the website links
for future updates. The last update for this ESA is May 31, 1989. |
DESCRIPTION:
Tall biennial (sometimes perennial in favorable locations) that reproduces from
seeds.
|
]Top 2 photos: © John M. Randall/The Nature Conservancy
Bottom 2 photos: © Barry M. Rice/The Nature Conservancy
|
RANGE: Conium
maculatum is a native of Europe, western Asia and North Africa. It was
brought to the United States from Europe as a garden plant. "Poison hemlock is
common and spreading in parts of the United States and Canada, particularly on
the West Coast; it is common and of some importance in New Zealand, and it also
occurs in South America and the British Isles. In Australia, it occurs
generally throughout the southern states but has occurred as far north as
Queensland" (Parsons 1973).
HABITAT: Conium
maculatum "commonly occurs in sizable stands of dense, rank growth
along roadsides, field margins, ditchbanks and in low-lying waste areas. It
also invades native plant communities in riparian woodlands and open flood
plains of rivers and streams in southern California" (Goeden and Ricker 1982)
and other regions in the state. It is common on shady or moist ground below
5000 feet, especially in cismontane California.
REPRODUCTION:
Life Cycle: In California, "poison hemlock reproduces only from seed, both as a
biennial and winter annual, and occasionally as a short-lived perennial"
(Goeden and Ricker 1982). "Seeds germinate in autumn and plants develop rapidly
throughout the winter and spring. Some produce flowering stems in the first
spring and die in the summer. Others remain in the vegetative stage without
producing flowering stems until the second spring, thus becoming a biennial.
Plants are more likely to be biennial in very moist situations. After producing
seeds, the plants die in the summer ... The spread of hemlock is by seeds which
can adhere to farm machinery, vehicles, agricultural produce, mud and clothing
as well as being carried by water and to a limited extent wind" (Parsons 1973).
"Hemlock is capable of rapid establishment after autumn rains, particularly on
disturbed sites or where little vegetation exists at the start of the autumn
growing season. Once it is firmly established under such conditions, hemlock
can preclude most other vegetation and established pastures" (Parsons 1973).
IMPACTS:
Conium maculatum can be a tenacious weed particularly in moist habitats
and along streams. Poison hemlock may act as a pioneer species quickly
colonizing disturbed sites and displacing natives during early successional
seres. The presence of C. maculatum degrades habitat quality and could
indicate a management problem on an ecological preserve. Conium maculatum
is poisonous to both humans and livestock. It was probably used to poison
Socrates. "Poisoning of humans has occurred after the ingestion of seeds,
leaves and roots and even as a result of blowing through the hollow stems when
used as whistles or pea-shooters. The seeds, however, are the most toxic part
of the plant. Extracts of hemlock have been used as arrow poisons by North
American Indians, and it was used medicinally for many years in treating
tumors, ulcers and gout" (Parsons 1973).
AUTHOR:
Don Pitcher
For more information
on poison hemlock, please contact:
Mid-Atlantic Exotic Pest Plant Council, Inc., http://www.ma-eppc.org
National Invasive Species Information Center,
http://www.invasivespeciesinfo.gov
The Nature Conservancy, Invasive Species Initiative,
http://tncweeds.ucdavis.edu/esadocs.html
USDA-NRCS PLANTS Database, http://plants.usda.gov/
REFERENCES:
Fairbairn, J. W. 1970. The alkaloids of hemlock. P.361-368 in V.H. Heyward
(ed.), Biology and chemistry of the Umbelliferae.
Fairbairn, J. W. and A.A.E.R. Ali. 1968. The alkaloids of hemlock (Conium
maculatum L.). III. The presence of bound forms in the plant. Phytochemistry
7:1593-1597.
Fairbairn, J. W. and S.B. Challen. 1959. The alkaloids of hemlock (Conium
maculatum L.). Distribution in relation to the development of the fruit.
Biochemistry Journal 72 (4): 556-61.
Fairbairn, J.W. 1968. The alkaloids of hemlock (Conium maculatum L.), IV:
Isotopic studies of the bound forms of alkaloids in the plant. Phytochemistry
7:1599-1603.
Freitag, J. H. and H. P. Severin. 1945. Poison-hemlock-ringspot virus and its
transmission by aphids to celery. Hilgardia 16(8) :389-410.
Frohne, D. and H. J. Pfander. 1983. A colour atlas of poisonous plants. Wolfe
Science, London. 291 pp.
Goeden, R. D. and D. W. Ricker. 1982. Poison hemlock, Conium Maculatum, in
southern California - an alien weed attacked by few insects. Annals of
Entomological Society of America 75: 173-176.
Howell, W. E. and G. I. Mink. 1981. Viruses isolated from wild carrot and
poison hemlock. Plant Diseases 65:277-279.
James, L. F. and A. E. Johnson. 1976. Some major plant toxicities of the
western U.S. Journal of range management 29: 356-363.
Jepson, W. L. 1951. Manual of the flowering plants of California. University of
California Press, Berkeley.
Kingsbury, J. M. 1964. Poisonous plants of the U.S. and Canada. Prentice-Hall,
Inc., Englewood Cliffs, NJ. 626 pp.
Leete, E. and N. Adityachaudhury. 1967. Biosynthesis of the hemlock alkaloids.
II. The conversion of -coniceine to coniine and -conhydrine. Phytochemistry
6:219-223.
Muenscher, W. C. 1975. Poisonous plants of the U.S. Collier Books, New York.
277pp.
Parsons, W. T. 1973. Noxious weeds of Victoria. Inkata Press, Ltd., Melbourne,
Australia. 300 pp.
Pemberton, A. W. and R. R. Frost. 1974. Celery mosaic virus in England. Plant
Pathology 23: 20-24.
Robbins, W. W. 1940. Alien plants growing without cultivation in California.
California Agricultural Experiment Station Bulletin 637:1-128.
Roberts, M. F. 1971. The formation of -coniceine from 5-ketooctanal by a
transaminase of Conium maculatum. Phytochemistry 10:3057-3060.
Roberts, M. F. 1974. An S-adrenasyl-1-methionin; conciine methyltransferase
from Conium maculatum. Phytochemistry 13: 1847-1851.
Roberts, M. F. and Richard T. Brown. 1981. A new alkaloid from South African
Conium species. Phytochemistry 20:447-449.
Roberts, M.F. 1975. Y-coniceine reductase in Conium maculatum. Phytochemistry
14: 2393-2397.
Simpson, B. H. 1975. Plant toxicities in sheep on a property with unusual weed
control problems. Proceedings 28th New Zealand Weed and Pest Control
Conference, pp. 92-94.
Stephens, H. A. 1980. Poisonous plants of the central U.S. The Regents Press of
Kansas, Lawrence. 165 pp.
Sutubutra, T. and R. N. Campbell. 1971. Strains of celery mosaic virus from
parsley and poison hemlock in california. Plant Disease Reporter 55: 328-332.
Tyler, H. A. 1975. The swallowtail butterflies of North America. Naturegraph
Publishing, Healdsburg, CA. 192 pp. USDA. 1980. Plants poisonous to livestock
in the western States.
USDA Agricultural Information Bulletin No. 415. 90pp. Vorobyov, N. E. 1960. On
some biological properties of biennial weeds of the Danube stepp. Ukrainsky
Botonichny Zhurnal 17(5) : 43-49.
Management and
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