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Plants
Hypericum perforatum
EOL Text
This introduced perennial plant is 1–2½' tall, branching frequently. The round stems are hairless and light green; the larger stems have a pair of small longitudinal ridges. The opposite leaves are about 1" long and 1/3" across. They are oblong, hairless, and sessile. The surface of these leaves is perforated by numerous translucid dots, and there are often scattered black dots along the margin of the lower surface. The upper stems terminate in flat-headed clusters of several flowers (cymes). Each flower is about ¾" across, consisting of 5 yellow petals, 5 green sepals, 3 styles, and numerous stamens (more than 20). There are scattered black dots along the margins of the petals. The sepals are lanceolate and much smaller than the petals. The blooming period occurs from early to mid-summer and lasts about a month. The petals turn brown and persist near the seed capsules, rather than falling to the ground. Each 3-celled seed capsule is well-rounded at the base, becoming conical at its apex. Each cell of the seed capsule contain numerous seeds, which are oblong, flattened, and black. The surface of each seed is somewhat roughened by numerous small pits, rather than smooth. The root system is rhizomatous, and produces numerous basal offshoots around the base of the plant.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Copyright © 2002-2014 by Dr. John Hilty |
Source | http://www.illinoiswildflowers.info/weeds/plants/cm_stjohnwort.htm |
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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
More info for the term: cover
SAF COVER TYPES [59]:
5 Balsam fir
14 Northern pin oak
16 Aspen
17 Pin cherry
18 Paper birch
19 Gray birch-red maple
20 White pine-northern red oak-red maple
21 Eastern white pine
25 Sugar maple-beech-yellow birch
26 Sugar maple-basswood
27 Sugar maple
28 Black cherry-maple
37 Northern white-cedar
39 Black ash-American elm-red maple
46 Eastern redcedar
50 Black locust
52 White oak-black oak-northern red oak
53 White oak
55 Northern red oak
60 Beech-sugar maple
63 Cottonwood
107 White spruce
108 Red maple
109 Hawthorn
110 Black oak
210 Interior Douglas-fir
212 Western larch
213 Grand fir
215 Western white pine
217 Aspen
218 Lodgepole pine
220 Rocky Mountain juniper
221 Red alder
222 Black cottonwood-willow
223 Sitka spruce
224 Western hemlock
225 Western hemlock-Sitka spruce
226 Coastal true fir-hemlock
227 Western redcedar-western hemlock
228 Western redcedar
229 Pacific Douglas-fir
230 Douglas-fir-western hemlock
231 Port-Orford-cedar
233 Oregon white oak
234 Douglas-fir-tanoak-Pacific madrone
235 Cottonwood-willow
237 Interior ponderosa pine
238 Western juniper
239 Pinyon-juniper
243 Sierra Nevada mixed conifer
244 Pacific ponderosa pine-Douglas-fir
245 Pacific ponderosa pine
246 California black oak
247 Jeffrey pine
248 Knobcone pine
249 Canyon live oak
250 Blue oak-foothills pine
255 California coast live oak
More info for the term: forb
Forb
Hypericum perforatum (Common St. John's Wort) introduced
(observations are from MacRae, Swengel & Swengel, and Grundel et al.; bees collect pollen, beetles feed on pollen, while the butterfly explores the flowers in vain for nectar; only pollen is available as a reward for flower visitors; information is limited to bees, beetles, and butterflies)
Bees (short-tongued)
Halictidae (Halictinae): Agapostemon splendens cp (Gnd), Lasioglossum leucocomum cp (Gnd), Lasioglossum pictum cp (Gnd), Lasioglossum pilosum cp (Gnd), Lasioglossum vierecki cp (Gnd); Andrenidae (Panurginae): Perdita halictoides cp (Gnd)
Butterflies
Lycaenidae: Lycaeides melissa samuelis exp (Sw)
Beetles
Buprestidae: Acmaeodera texana fp (McR), Acmaeodera tubulus fp (McR)
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Copyright © 2002-2015 by Dr. John Hilty |
Source | http://www.illinoiswildflowers.info/flower_insects//plants/cm_stjohn.html |
St Johnswort is native to Europe, western Asia, and North Africa, and is now widely distributed through the temperate areas of the world including parts of South America, India, New Zealand, Australia, and South Africa. St Johnswort is considered a weed in much of its native range, particularly in Turkey, Italy, France, Hungary, and Sweden, mainly in poor pastures, neglected areas, and occasionally in crops [139]. Its wide distribution may in part be attributed to its cultivation as a medicinal or garden plant [45].
In Canada, St Johnswort is found mostly in the eastern provinces and British Columbia, and is absent in the prairie region [45,99]. In the U.S., St Johnswort is distributed from Minnesota south to central Texas, east to the Atlantic Coast, and west to the northern Pacific coaSt Plants database provides a state distribution map of St Johnswort.
St Johnswort was likely introduced to North America multiple times [121]. According to Sampson and Parker [154], who review its history of introduction in North America, the 1st recorded occurrence of St Johnswort in North America was from Pennsylvania in 1793. St Johnswort was established in many western states by the early 1900s. The majority of St Johnswort infestations at that time occurred in 2 regions: the western coastal region, including northern California, western Oregon, and western Washington; and the Interior West, including northeastern Oregon, eastern Washington, northern Idaho, and northwestern Montana [78,142]. By 1945, St Johnswort infested about 2.5 million acres (1 million ha) in California, and about 1.2 million acres (500,000 ha) in Idaho, Oregon, and Washington [177]. In central North America, St Johnswort never reached the densities observed in the West, likely because cropland habitat is not ideal for St Johnswort [121].
St Johnswort population levels were dramatically reduced following a successful biological control program begun more than 50 years ago in heavily infested regions in the western U.S. [93,177]. According to Piper [143], in other areas many St Johnswort populations are still increasing in size, even where biological control organisms are present, while others have remained relatively static. A reliable published estimate of the amount of land presently infested by St Johnswort is not available [143]. Additionally, whether biocontrol in the West is currently as efficacious as it was initially is not well documented [121].
The following lists include vegetation types in which St Johnswort is known to be or thought to be potentially invasive, based on reported occurrence and biological tolerances to site conditions. Some habitats that may be invaded by St Johnswort following soil and/or vegetation disturbances are also included. Precise distribution information is limited, especially in central and eastern North America; therefore, these lists may not be exhaustive.
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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
More info for the term: shrub
KUCHLER [107] PLANT ASSOCIATIONS:
K001 Spruce-cedar-hemlock forest
K002 Cedar-hemlock-Douglas-fir forest
K003 Silver fir-Douglas-fir forest
K004 Fir-hemlock forest
K005 Mixed conifer forest
K006 Redwood forest
K009 Pine-cypress forest
K010 Ponderosa shrub forest
K011 Western ponderosa forest
K012 Douglas-fir forest
K013 Cedar-hemlock-pine forest
K014 Grand fir-Douglas-fir forest
K016 Eastern ponderosa forest
K017 Black Hills pine forest
K018 Pine-Douglas-fir forest
K023 Juniper-pinyon woodland
K024 Juniper steppe woodland
K025 Alder-ash forest
K026 Oregon oakwoods
K028 Mosaic of K002 and K026
K029 California mixed evergreen forest
K030 California oakwoods
K033 Chaparral
K034 Montane chaparral
K035 Coastal sagebrush
K036 Mosaic of K030 and K035
K047 Fescue-oatgrass
K048 California steppe
K050 Fescue-wheatgrass
K051 Wheatgrass-bluegrass
K055 Sagebrush steppe
K056 Wheatgrass-needlegrass shrubsteppe
K063 Foothills prairie
K073 Northern cordgrass prairie
K074 Bluestem prairie
K082 Mosaic of K074 and K100
K093 Great Lakes spruce-fir forest
K095 Great Lakes pine forest
K098 Northern floodplain forest
K099 Maple-basswood forest
K100 Oak-hickory forest
K101 Elm-ash forest
K102 Beech-maple forest
K103 Mixed mesophytic forest
K104 Appalachian oak forest
K106 Northern hardwoods
K109 Transition between K104 and K106
K111 Oak-hickory-pine
K112 Southern mixed forest
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More info for the term: cover
St Johnswort seeds germinate in autumn, winter, or spring. Erect woody stems develop in late winter to spring. Flowering and pollen production begin late spring to early summer and continue well into summer, although 1st-year plants do not flower. By mid-summer most petals have withered; seed capsules are moist, green, and sticky; and seeds are green. In early autumn few petals remain, and capsules dry and become less sticky. By late autumn all petals have gone, flowering stems are dry, and capsules contain ripe seeds. Dry flowering stems remain standing for several months, sometimes years [34,45,139,178].
Fall and winter rains initiate procumbent growth in St Johnswort, with prostrate, nonflowering stems up to 12 inches (30 cm) long [34,45,121]. Foliage may be thick on these stems and form a thick mat that smothers other vegetation [34,139]. St Johnswort overwinters in this form, and by seed [45]. Procumbent stems die in late spring [34].
The general phenological pattern observed on a study area in northern Idaho from 1950 through 1956 was as follows [178]:
Drainage | Elevation (feet) | Start of upright shoots | Early bloom | Late bloom | Early fruit | Ripe seed |
Clearwater | 1,200 | 1st week April | 1st week June | 2nd week July | 4th week July | 2nd week September |
Salmon | 1,800 | 2nd week April | 2nd week June | 2nd-3rd week July | 4th week July | 2nd week September |
Palouse | 3,500 | 4th week April | 3rd week June | 4th week July | 1st week August | 2nd-3rd week September |
In northern Idaho, St Johnswort remained green longer than most of the associated vegetation including native perennials. Most seed was ripe by mid-September, and seed dissemination occurred through October and November. At most sites, and in 4 of the 7 years during the observation period, St Johnswort produced fall procumbent basal growth, varying from about 1 to 5 inches (2-13 cm) long. Some winter damage to fall growth was noted, especially on sites with erratic snow cover [178]. Walker [189] provides detailed observations of timing of flowering and seed production at a site in Oregon.
Flowering dates in other parts of North America are given as follows:
Geographic area | Flowering dates | Reference |
CA | June to September | [136] |
KS | June to October | [9] |
southeastern MI | June 19 to August 16 | [57] |
NV | June to September | [100] |
TX | June to September | [52] |
WV | June-September | [168] |
Adirondack area | July 11 through summer | [108] |
Blue Ridge | June to August | [199] |
Carolinas | June to September | [145] |
Great Plains | June to August | [69] |
north Atlantic coast | June to September | [54] |
northeastern U.S. | June to September | [67] |
NS | July 10-August | [152] |
eastern Canada | late June to August | [45] |
(key to state/province abbreviations)
UNITED STATES
AR | CA | CO | CT | DE | GA | HI | ID | IL | IN |
IA | KS | KY | LA | ME | MD | MA | MI | MN | MS |
MO | MT | NE | NV | NH | NJ | NY | NC | ND | OH |
OK | OR | PA | RI | SC | SD | TN | TX | VT | VA |
WA | WV | WI | WY | DC |
CANADA
BC | NB | NF | NS | ON | PE | PQ |
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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
ECOSYSTEMS [66]:
FRES10 White-red-jack pine
FRES11 Spruce-fir
FRES14 Oak-pine
FRES15 Oak-hickory
FRES17 Elm-ash-cottonwood
FRES18 Maple-beech-birch
FRES19 Aspen-birch
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES22 Western white pine
FRES23 Fir-spruce
FRES24 Hemlock-Sitka spruce
FRES25 Larch
FRES26 Lodgepole pine
FRES27 Redwood
FRES28 Western hardwoods
FRES29 Sagebrush
FRES34 Chaparral-mountain shrub
FRES35 Pinyon-juniper
FRES36 Mountain grasslands
FRES37 Mountain meadows
FRES38 Plains grasslands
FRES39 Prairie
FRES41 Wet grasslands
FRES42 Annual grasslands