Roots:
The roots of this plant are an abbreviated taproot system. The roots
branch deeply into the earth, however some of them do not and are
shallow,
these are usually the ones that reproduce. (1)
Stems/Leaves: This plant has numerous erect stems, that appear
rust colored. (1)
The stems are also woody and grow any where from 30-120 cm tall,
(2-5ft).
The leaves of this plant are oblong and/or elliptic, they contain
transparent
glands, which produce an oil that makes animals photosensitive. (1,2)
These
leaves are attached directly to the stem and the edges of the leaves
contain
tiny black dots.
Flowers: These flowers are anywhere from 1 to 2 cm in diameter,
they are yellow
and develop in clusters. Each flower consists of five petals,
there
are also transparent black dots around the edges of each petal. (1) The
flowering period of this plant is May through September. This flower
also
contains numerous stamens. (1,2)
Fruits/Seeds: The seed capsules of this plant are rounded at the
end, and all of
them are about 5mm long. They are rusty in color and each capsule
contains
numerous seeds. These seeds are brown (almost black) in color and are
any
where from 0.6 to 0.7 mm long. Each seed contains a germination
inhibitor,
but the germination increases over time during rainy periods because
the
inhibitor is washed off. (1)
Methods of Reproduction/Spread: Reproduction is through seeds
and roots. Seeds can be dispersed by the wind,
wild life, and of course by humans. (1)
The seeds can be carried in animal's digestive tract. They are only
carried short distances by wind, but can be carried far by water,
animals, and machinery. (7)
Life Style/ Habits/ Life Duration: St. Johnswort grows in fields
and can push out native plants. It is
a perrenial, which means it comes back every year from the roots. (1)
It commonly grows in grasslands, woodlands, open forest, pastures,
forestry, roadsides, railway lines, and river banks. (7)
Impacts:
This weed has many impacts. It produces an oil from a gland that forms
on the leaf, this oil can cause animals to blister, develop rashes,
loose
weight, be supersensitive to light, and if the animal eats to much it
can
even die. It also out competes the native North American vegitation
decreasing
the available forage for wildlife and ranching. (1)
Native Range:
The native range of this weed is Western Europe, Northern Africa, parts
of Asia, India, China, and Japan. (2)
Chemical control:
Chemical control for this plant is: selective herbicides. (4)
Cultural
Control: Includes: 1) repeated cultivation, which destroys it,
and 2) mowing
it over and over again, so seeds do not mature. (4)
Biological
Control: Includes:
Agrilus hyperici,
Aplocera
plagiata,
Chrysolina
hyperici,
Chrysolina quadrigemina and
Zeuxidiplosis
giardi. (3)
Other: St. John's Wort is
used for many medicinal purposes including: Depression, Bacterial
Infections, Seasonal Affective Disorder, Viral encephalitits, and ear
infections. (6)
Links:
http://www.healthy.net/scr/Article.asp?Id=915
http://en.wikipedia.org/wiki/Saint_John's_wort
http://www.stevenfoster.com/education/monograph/hypericum.html
http://plants.usda.gov/java/profile?symbol=HYPE
http://www.wwf.org.uk/filelibrary/pdf/hperforatum.pdf
http://www.holoweb.com/cannon/stjohns.htm
Bibliography
1. Rees, Nornan, et. al., Ed.,
Biological Control of Weeds in the
West, Western Society of weed Science, in cooperation with USDA
ARS,
MT Dept. of Ag. and MT State Univ., Color World Printers, Bozeman, MT,
Feb., 1995.
2. Bradfield, Patsy, Executive Secretary. St. Johnswort (Hypericum
perforatum). http://www.pprl.usu.edu/stl.htm, 9-30-99.
3. Breitenfeldt, Todd, Personal Interview, Biology Teacher,
Whitehall
Schools, Box 1109, Whitehall, MT 59759. (406)287-3862. 9-2-99.
4. Henry, Charlie, Executive Secretary for CWMA. St. Johnswort (Hypericum
perforatum) [Online] Available:
http://www.fortnet.org/CWMA/stjohn.htm
9-30-99.
5. Created by: Jiasuey and Allaire, Wellesley College, Common
St. Johnswort, Hypericum perforatum, Family Guttiferae [Online]
Available:
http://www.wellesley.edu/Activities/homepage/web/Species/pstjohnswort.html
9-30-99.
6. UMMC. April 2002. University of Maryland Medical Center. 20
Feb. 2007. <http://www.umm.edu/altmed/ConsHerbs/StJohnsWortch.html>
7. DPI. May 2003. Department of Primary Industries. 20 Feb. 2007
<http://www.dpi.vic.gov.au/dpi/nreninf.nsf/LinkView/286F120ECF6C683BCA256BCF000AD54AECC844336D72F0634A256DEA00293F8A>
By:
Kristen Chadwick 11/16/99.
Updated by:
CRH 2/07
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Scientific/Common
Names: