Common St. Johnswort or Klamathweed [Hypericum perforatum L.][HYPPE][CDFA
list: C] Photographs
goatweed, tipton weed, St. Johns wort
DESCRIPTION:Erect noxious perennial, to 1.2 m tall, with
rhizomes and showy, bright yellow flowers.
Foliage is dotted with tiny translucent and black oil
glands that contain hypericin, a fluorescent red pigment that
is toxic to livestock when consumed in quantity, especially
to animals with light-colored skin. Toxicity symptoms include
skin photosensitivity of light-colored areas and loss of condition.
Most animals graze plants only when more desirable forage is unavailable.
In herbal medicine, hypericin is the antidepressant ingredient
in St. Johnswort remedies. There are several regional varieties
of common St. Johnswort. The variety in the Pacific Northwest
is aggressively competitive and can spread rapidly by seed and
rhizomes. By 1940, more than 2 million hectares (~ 1 million ha
in California) of rangelands were infested. Several years later,
the leaf-feeding flea beetles Chrysolina quadrigemina and
C. hyperici and the root-boring beetle Agrilus hyperici
were successfully introduced as biocontrol agents. Today infestations
of the weed have been reduced by 97 to 99 %. Localized outbreaks
of the plant sometimes occur after disturbances such as logging,
fire, or during low population cycles of the flea and root-boring
beetles. Introduced from Europe where it has been used medicinally
lanceolate to ovate, 1.5-3 mm long, 1-2 mm wide. Subsequent leaves
opposite, oval to elliptic, increasingly larger. Underside leaf
margins dotted with a few elevated black glands.
with numerous sterile shoots 2-10 cm long from the lower leaf
axils, highly branched near the top, glabrous, often reddish,
with black glands along 2 longitudinal ridges. Leaves opposite,
elliptic-oblong to linear, 1-3 cm long, sessile, flat, glabrous,
green, 3- to 5-veined from the base, dotted with numerous,
tiny translucent glands that are visible when a leaf is held
up to the light. Edges of leaf lower surfaces lined with elevated
black glands. Margins rolled under (revolute).
and UNDERGROUND STRUCTURES:Taproots stout, with many branched lateral roots,
to ~ 1.5 m deep. Rhizomes develop just below the soil surface
from the crown and can extend outwards to ~ 0.5 m. New shoots
grow from the crown and rhizomes in early spring. Fragmented rhizomes
can develop new plants. Under favorable conditions, roots grow
deeper and fewer rhizomes develop. Specialized corky tissue (polyderm),
found only in a few plant families, protects the roots and crowns.
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Flowers bright yellow, ~ 2 cm in diameter, clustered at
the stem tips. Petals 5, separate, 8-12 mm long, typically
dotted with black glands along the margins. Sepals
5, linear-lanceolate, 4-5 mm long, much shorter than petals.
Stamens yellow, numerous. Styles 3, 3-10 mm long.
Plants typically do not flower the first year. Insect pollinated
and apomictic (seed develops without pollination).
and SEEDS:Capsules 3-chambered, ovate, not lobed,
sticky-glandular, 5-10 mm long, with persistent styles 3-10 mm
long, open longitudinally to release seed. Seed shiny black to
brown, nearly cylindrical, ~ 1 mm long, densely pitted, often
coated with gelatinous material from the capsule that aids dispersal
and may inhibit germination until it breaks down or leaches out
in about 4-6 months.
CHARACTERISTICS:Aerial growth dies back during the cold season.
In forested or wildland areas, dry flower stems can contribute
to fire hazard risks.
and pastures (especially when poorly managed), fields, roadsides,
forest clearings in temperate regions with cool, moist winters
and dry summers. Grows best in open, disturbed sites and on slightly
acidic to neutral soils. Does not tolerate saturated soils.
region, Cascade Range, northern and central Sierra Nevada, Sacramento
Valley, San Francisco Bay region, Central Coast, Peninsular Ranges;
to Canada; Eastern U.S. To 1500 m (4900 ft).
by seed and vegetatively from
rhizomes. Plants can develop seed with or without pollination
(facultative apomixis). Seed and capsules disperse with water
and adhere to machinery, tires, shoes, clothing, and feet, fur,
or feathers of animals. Seeds are hard-coated, and those consumed
by animals remain intact and viable. Seeds from plants in the
Pacific Northwest usually do not require an after-ripening period.
Germination occurs fall through spring. Brief exposure to fire
(100-140º C, 212-284º F) often increases germination.
Calcium ions in water appears to inhibit germination of some biotypes.
Seed can remain viable for ~10 years or more in the soil and for
at least 5 years submerged in fresh water. Plants typically produce
an average of 15,000-33,000 seeds per plant. Seedlings survive
best on disturbed open sites.
FAVORING/DISCOURAGING SURVIVAL:Releasing the leaf-feeding beetle Chrysolina
quadrigemina on uninfested plant populations can eventually
give excellent long-term control. Cultivation readily controls
plants on agricultural lands. Improving soil fertility and reseeding
with desirable vegetation can help reduce or eliminate infestations
in pastures. Mowing and overgrazing reduces seed production, but
promotes vegetative spread from rhizomes. Burning stimulates seed
germination and vegetative reproduction.
SPECIES:Dwarf St. Johnswort
[Hypericum mutilum L.] is an uncommon erect annual to
perennial to ~ 0.6 m tall that is distinguished by
having petals +/- 2 mm long, sepals equal to or slightly
longer than the petals, styles ~ 1 mm long, and 1-chambered
capsules. Dwarf St. Johnswort occurs in moist places
or riparian woodlands in the central-eastern Sacramento Valley
and adjacent Sierra Nevada foothills to 300 m (1000 ft). It is
introduced from eastern North America and expected to expand range.
Canary Island St. Johnswort [Hypericum canariense
L.][CalEPPC: Need more information] is an ornamental shrub with
large flowers that has escaped cultivation in some places. Canary
Island St. Johnswort grows to 4(5) m tall, has narrowly
+/- elliptic leaves 2-7 cm long with wedge-shaped bases,
sepals lined with hairs along the margins (ciliate), petals
and stamens that persist after flowering, and
leathery capsules that open at maturity. It occurs
in disturbed places, coastal sage scrub, and grassland in the
South Coast (especially San Diego area), to 100 m (330 ft). In
addition, three native Hypericum species occur in roughly
the same regions as common St. Johnswort. However, native
species have at least one of the following characteristics: +/-
prostrate habit with matted stolons, linear to
lanceolate leaves with acute tips and
usually folded along the midrib, sterile shoots at the
base to 2 cm long, and 3-lobed capsules.
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