Plant Assessment Form

Hypericum perforatum

Common Names: St. John's wort; klamathweed; tipton weed; goatweed

Evaluated on: 26-Jul-04

List committee review date: 27/08/2004

Re-evaluation date:

Evaluator(s)

Carri Pirosko, Associate Agricultural Biologist
California Department of Food and Agriculture, Noxious Weed Program
20235 Charlanne Drive, Redding, CA 96002
(530) 545-9119
cpirosko@cdfa.ca.gov
Joseph M. DiTomaso
University of California
Weed Science Program, Robbins Hall, Davis, CA 95616
530-754-8715
ditomaso@vegmail.ucdavis.edu

List commitee members

Cynthia Roye
John Randall
Jake Sigg
Peter Warner
Joe DiTomaso
Alison Stanton

General Comments

No choice is available for the DBAD selection in the impact section: selected B per List Committee.

Table 2. Criteria, Section, and Overall Scores

Overall Score? Limited
Alert Status? No Alert
Documentation? 3.5 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes D Reviewed Scientific Publication
Impact?
Four-part score DBAD Total Score
Could not calculate
1.2 ?Impact on plant community B. Moderate Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels A. Severe Reviewed Scientific Publication
1.4 ?Impact on genetic integrity D. None Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Invasiveness?
Total Points
11 Total Score B
2.2 ?Local rate of spread with no management B. Increases less rapidly Reviewed Scientific Publication
2.3 ?Recent trend in total area infested within state C. Stable Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal C. Low Reviewed Scientific Publication
2.6 ? Potential for natural long-distance dispersal C. Rare Reviewed Scientific Publication
2.7 ?Other regions invaded C. Already invaded Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Reviewed Scientific Publication
Distribution?
Total Score B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
C. Low Observational

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".

Section 1: Impact
Question 1.1 Impact on abiotic ecosystem processes? D Reviewed Scientific Publication
Identify ecosystem processes impacted:

Not much mentioned in the literature, increased fire hazard form dried plant material is all that was found, but this is probably rare. in forested or wildland areas, dry flower stems can contribute to fire hazard risks


Sources of information:

Weeds of California and Other Western States, J.M. DiTomaso and E.Healy, as yet published


Question 1.2 Impact on plant community composition,
structure, and interactions?
B Reviewed Scientific Publication
Identify type of impact or alteration:

see referenced materials below Dense stands can be a problem in pastures and rangelands because they displace native and indigenous plant species; the displacement of native and indigenous plant species may depreciate wildlife carrying capacity. Plant monocultures decrease biodiversity and increase a plant community's vulnerability to disease.
Displaces desirable indigenous plant species and valued livestock forage
*Can become established in either highly degraded or pristine rangelands.
Hypericum perforatum is a particularly aggressive weed of rangeland characterized by dry summers. Its deep root system is capable of supporting the plant when the water available to more desirable species has been depleted. It forms a dense spreading canopy up to 1 m tall and large infestation covered over 1 million ha. in western N. America before biocontrol implementation.


Sources of information:

The Biology of Canadian Weeds. 83. Hypericum perforatum. C.W. Crompton, V. Hall, K.I.N. Jensen, and P.D. Hildebrand. Canadian J. Plant Sci. 68:149-162 (Jan 1988); Biology and Management of Noxious Rangland Weeds, Sheley and Petroff. (ST. Johnswort. Gary L. Piper); Krueger, J. and R. Sheley. Montana State University, Extension Service Montguide, MT199810 AG, St. Johnswort, July 2002; Sampson, A.W. and K.W. Parker, 1930. St. Johnswort on Range Lands of California. University of California College of Agriculture, Agricultural Experiment Station, Berkeley, California. Bulletin 503, December 1930, University of California Printing Office, Berkeley, California.


Question 1.3 Impact on higher trophic levels? A Reviewed Scientific Publication
Identify type of impact or alteration:

Displacement of wildlife and livestock. Can greatly depreciate livestock and wildlife carrying capacities, and endanger the biological diversity of grazing lands;
Displaces desirable wildlife; toxic to livestock


Sources of information:

Biology and Management of Noxious Rangland Weeds, Sheley and Petroff. (ST. Johnswort. Gary L. Piper)


Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

Only known hybridization not with native CA species. H. perforatum has been artificially hybridized with other species of the genus; There are numerous cultivated hybrids in existance, none with native flora of California though.


Sources of information:

The Biology of Canadian Weeds. 83. Hypericum perforatum. C.W. Crompton, V. Hall, K.I.N. Jensen, and P.D. Hildebrand. Canadian J. Plant Sci. 68:149-162 (Jan 1988).


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
B Reviewed Scientific Publication
Describe role of disturbance:

Good deal of both types disturbance- lead to establishment, although, one source found citing establishment into a pristine rangeland. Seed are disseminated short distances by the wind; long distances by adherence to animals (facilitated by a gelatinous seed coat), animal ingestion and subsequent deposition in feces, water movement, and through the activities of humans.
*Can be established in either highly degraded or pristine rangelands


Sources of information:

Krueger, J. and R. Sheley. Montana State University, Extension Service Montguide, MT199810 AG, St. Johnswort, July 2002; Sampson, A.W. and K.W. Parker, 1930. St. Johnswort on Range Lands of California. University of California College of Agriculture, Agricultural Experiment Station, Berkeley, California. Bulletin 503, December 1930, University of California Printing Office, Berkeley, California.


Question 2.2 Local rate of spread with no management? B Reviewed Scientific Publication
Describe rate of spread:

This weed can spread agressively within a patch/site with no competition in particular, but new seedlings do not compete well. Spread will only be temporary because of presence of biological control agent. Hypericum perforatum is a particularly agressive weed of rangeland characterized by dry summers. Its deep root system is capable of supporting the plant when the water available to more desirable species has been depleted. It forms a dense spreading canopy up to 1 m tall and large infestation covered over 1 million ha. in western N. America before biocontrol implementation.
Seedlings are very small, grow slowly and compete poorly with other vegetation.
The seedlings are not stong competitors with other vegetation for light, nutrients, space, and moisture, and may exhibit high mortality under stress conditions.


Sources of information:

The Biology of Canadian Weeds. 83. Hypericum perforatum. C.W. Crompton, V. Hall, K.I.N. Jensen, and P.D. Hildebrand. Canadian J. Plant Sci. 68:149-162 (Jan 1988). Biology and Management of Noxious Rangland Weeds, Sheley and Petroff. (ST. Johnswort. Gary L. Piper)


Question 2.3 Recent trend in total area infested within state? C Observational
Describe trend:

Seems to be increasing along roadsides at higher elevations in the NE part of the state, but populations eventually decline because of biological control agents.
Fluxuations occur naturally, cycling up and down, with fluxes in bioagent populations
Localized outbreaks of the plant sometimes occur after disturbances such as logging, fire or during low population cycles of the bioagents
Many St. Johnswort populations are still increasing in size, while others have remained static or decreased. Unfortunately, a reliable published estimate of the amount of land presently infested by St. Johnswort is not available. In the 1940s it occupied over 1 million acres and today it is only about 1% of that, or less. Varies widely across the state, especially once you factor in elevational differences (bioagents can't survive); At this time ( July 26, 2004) this weed seems to be increasing total area infested- personal observation and in speaking with other land managers; we could just be in a down-swing of the bioagent populations.


Sources of information:

Weeds of California and Other Western States, J.M. DiTomaso and E.Healy, as yet published; Biology and Management of Noxious Rangland Weeds, Sheley and Petroff. (ST. Johnswort. Gary L. Piper)


Question 2.4 Innate reproductive potential? A Reviewed Scientific Publication
Describe key reproductive characteristics:

Reproduces by seed and vegetatively by rhizomes! Rhizomes have a protective tissue around them, making them hardier- and seeds have hard coat to aid in dispersal;survival. Plants typically produce an average of 15,000-33,000 seeds per plant. Seed can remain viable 10+ years.
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.


Sources of information:

Weeds of California and Other Western States, J.M. DiTomaso and E.Healy, as yet published; Krueger, J. and R. Sheley. Montana State University, Extension Service Montguide, MT199810 AG, St. Johnswort, July 2002; Sampson, A.W. and K.W. Parker, 1930. St. Johnswort on Range Lands of California. University of California College of Agriculture, Agricultural Experiment Station, Berkeley, California. Bulletin 503, December 1930, University of California Printing Office, Berkeley, California.


Question 2.5 Potential for human-caused dispersal? C Reviewed Scientific Publication
Identify dispersal mechanisms:

Human caused disturbances and gardening largest methods of human-caused dispersal. Long distance dispersal by humans into wildlands is probably uncommon. Sometimes cultivated like a crop or grown in herb gardens; Herbal medicine, hypericin is the antidepressant ingredient in St. Johnswort remedies
Localized outbreaks of the plant sometimes occur after disturbances such as logging, fire or during low population cycles of the bioagents.


Sources of information:

Weeds of California and Other Western States, J.M. DiTomaso and E.Healy, as yet published


Question 2.6 Potential for natural long-distance dispersal? C Reviewed Scientific Publication
Identify dispersal mechanisms:

Some potenial for long distance movement, expecially due to hard, small seeds. However, the vast majority of seed (>99.9%) probably fall directly below parent plant. seed and capsules can disperse with water and adhere to fur, feather of animals; seed are hard-coated and most ingested by animals remain intact and viable, but these mechanisms only account for movement of a very small proportion of the seed.


Sources of information:

Krueger, J. and R. Sheley. Montana State University, Extension Service Montguide, MT199810 AG, St. Johnswort, July 2002; Sampson, A.W. and K.W. Parker, 1930. St. Johnswort on Range Lands of California. University of California College of Agriculture, Agricultural Experiment Station, Berkeley, California. Bulletin 503, December 1930, University of California Printing Office, Berkeley, California.


Question 2.7 Other regions invaded? C Reviewed Scientific Publication
Identify other regions:

Northwestern region, Cascade Range, northern and central Sierra Nevada, Sacramento Valley, San Francisco Bay region, Central Coast, Peninsular Ranges, to 1500m.
Most contiguous states except Arizona, New Mexico, Utah, Alabama, and Florida.
south-eastern Australia, Eastern Canada and British Columbia;
In California and E. Canada- populations of H. perforatum have been found to be more and weedy; In Britian and Eastern Canada, this weed is a minor problem
Widespread in: Europe, Asia, N. and S. Africa, Australia, and western and eastern N. America Invades elsewhere but only in ecological types that it has already invaded in the state.


Sources of information:

Weeds of California and Other Western States, J.M. DiTomaso and E.Healy, as yet published


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? A Reviewed Scientific Publication

Rangeland areas and pastures, especially those that are poorly managed, fields, roadsides, and forest clearings or burned areas in temperate regions with cool, moist winters and dry summers. Grows best on open, disturbed sits on slighly acidic to neutral soils. Does not tolerate water saturated soils.
By 1940 more than 1 million acres of rangeland and was infested- several years later biological control agents were released - the bioagents tended to only survive below 1500 m- dramatically reducing infestation across the Pacific Northwest.
Seems to be increasing along roadsides at higher elevations in the NE part of the state; Small populations still exist in shady areas, boggy situations, north-facing slopes, and roadsides where the beetles are less active.
Fluctuations occur naturally, cycling up and down, with fluxes in bioagent populations
Localized outbreaks of the plant sometimes occur after disturbances such as logging, fire or during low population cycles of the bioagents.


Sources of information:

Weeds of California and Other Western States, J.M. DiTomaso and E.Healy, as yet published; Poisonous Plants of California, Fuller, T.C. et al. pp179-180; Sampson, A.W. and K.W. Parker, 1930. St. Johnswort on Range Lands of California. University of California College of Agriculture, Agricultural Experiment Station, Berkeley, California. Bulletin 503, December 1930, University of California Printing Office, Berkeley, California.


Question 3.2 Distribution/Peak frequency? C Observational
Describe distribution:

See question above, 3.1 See question above, 3.1


Sources of information:

See question above, 3.1


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes
Dense infestations produce >1,000 viable seed per square meter Yes
Populations of this species produce seeds every year. Yes
Seed production sustained over 3 or more months within a population annually Yes
Seeds remain viable in soil for three or more years Yes
Viable seed produced with both self-pollination and cross-pollination Yes
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes
Total points: 10
Total unknowns: 0
Total score: A?

Related traits:

plants can develop seed with or without pollination (facultative apomixis); seedlings may require several years to reach reproductive maturity, a population has all stages of growth though

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)
Major Ecological Types Minor Ecological Types Code?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieC, 5% - 20%
valley and foothill grasslandC, 5% - 20%
Great Basin grasslandC, 5% - 20%
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forest
riparian woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodlandC, 5% - 20%
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forestC, 5% - 20%
North Coast coniferous forestD, < 5%
closed cone coniferous forestD, < 5%
lower montane coniferous forestD, < 5%
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): A
Distribution (highest score): C

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Central West
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest
  • Modoc Plateau