Editing Hypericum perforatum (section)

== Ecology ==
=== Reproduction ===
[[File:Bombus terrestris P1140477a.jpg|thumb|200x200px|''[[Bombus terrestris]]'' pollinating the flowers of ''Hypericum perforatum'']]
St John's wort reproduces both [[Vegetative reproduction|vegetatively]] and [[Sexual reproduction|sexually]]. Depending on environmental and climatic conditions, and the age of the plant, St John's wort will alter the way it grows to promote survival. Summer rains are particularly effective in allowing the plant to grow vegetatively, following [[defoliation]] by insects or grazing.<ref name="BioactiveMolecules">Ramawat, Kishan Gopal. ''Bioactive Molecules and Medicinal Plants''. Springer Science & Business Media, 2008. p. 152. {{ISBN|978-3-540-74603-4}}</ref> St John's wort may also produce viable [[Apomixis|seeds without fertilization]].<ref name="FSControl" /> Its seeds can persist for decades while lying dormant underground in an ecosystem's [[soil seed bank]], germinating after they are disturbed.<ref name="feis" /><ref name="cabi" />

=== Diseases ===
''H. perforatum'' is affected by [[phytoplasma]] diseases, and when infected with [[Candidatus Phytoplasma fraxini|''Candidatus'' phytoplasma fraxini]] it shows visible symptoms, including yellowing and deformities called [[witch's broom]]. Its chemical profile is also altered: naphthodianthrone, [[flavonoid]], [[amentoflavone]], and pseudohypericin levels are reduced; [[chlorogenic acid]] levels are increased. Additionally, phytoplasma diseases greatly reduce the essential oil yield of the plant.<ref>{{cite journal |last1=Marcone |first1=C. |last2=Bellardi |first2=M.G. |last3=Bertaccini |first3=A. |title=Phytoplasma diseases of medicinal and aromatic plants |journal=Journal of Plant Pathology |date=2016 |volume=98 |issue=3 |pages=379–404 |doi=10.4454/JPP.V98I3.060 |jstor=44280481 }}</ref>

Dieback among populations of St John's wort is also caused by fungal [[anthracnose]], such as ''[[Glomerella cingulata|Colletotrichum gloeosporioides]].'' This fungus causes the stems to lose their bark ([[girdling]]) and turn brown, and dries the aboveground parts of the plant. The infection often kills the plant within the first year of its growth, or reduces productivity over a three-year deterioration.<ref>Ernst 2003, pp. 23, 41.</ref>

=== Role as a herbivore food source ===
Though ''Hypericum perforatum'' is generally avoided by mammalian herbivores, a number of insects are dependent on it and its close relatives as a food source. ''[[Chrysolina quadrigemina]]'' and ''[[Chrysolina hyperici|C. hyperici]]'' are two beetle species that feed on plants from the genus ''Hypericum'', including ''H. perforatum''. ''Chrysolina quadrigemina'' can be colored metallic blue, purple, green, or bronze and is better adapted to warm and dry climates; ''Chrysolina hyperici'' is consistently smaller, metallic green, and tends to live in areas with wetter and cooler conditions.<ref name="CanadaAg">{{cite journal |last1=Harris |first1=P. |last2=Peschkin |first2=D. P. |title=Biological Control of St. Johns-Wort |journal=Canada Agriculture |date=1974 |volume=19 |issue=1 |pages=13–15 |url=https://archive.org/details/canadaagricultur191cana/page/13 |publisher=Canada Department of Agriculture |location=Ottawa, Canada}}</ref> Another ''Hyericum'' specialist beetle is ''[[Agrilus hyperici]]'', the St John's wort root borer, whose [[larva]]e feed on the roots of ''H. perforatum'' while the adults feed on the foliage.<ref>{{cite book |editor1-last=Copping |editor1-first=L.G. |title=The manual of biocontrol agents: a world compendium |date=2004 |publisher=British Crop Protection Council |location=Alton, Hampshire, United Kingdom |isbn=1-901396-35-5 |pages=270–271 |edition=Third |url=https://archive.org/details/manualofbiocontr0000unse/page/270 |access-date=2 August 2023}}</ref>

A moth, ''[[Treble-bar|Aplocera plagiata]]'', feeds heavily upon the leaves of ''H. perforatum'' as a caterpillar and is commonly known as the common St John's wort inchworm. As adults, they are a small moth with gray wings and dark gray bands.<ref name="FSControl">{{cite book |last1=Winston |first1=Rachel |last2=Randall |first2=Carol Bell |last3=Schwarzländer |first3=Mark |last4=Reardon |first4=Richard |title=Biology and Biological Control of Common St. Johnswort |date=2010 |publisher=U.S. Dept. of Agriculture, Forest Service, FHTET |location=Morgantown, West Virginia |url=https://archive.org/details/CAT31080043 |access-date=2 August 2023}}</ref> Another moth that feeds upon ''H. perforatum'' is ''[[Euspilapteryx auroguttella]]''. Their caterpillars start by mining the inside of the leaves and later roll the leaves into cigar shapes to feed in greater safety.<ref>{{cite web|url=http://www.bladmineerders.nl/minersf/lepidopteramin/euspilapteryx/auroguttella/auroguttella.htm|title=bladmineerders.nl|author=|date=|website=bladmineerders.nl|accessdate=18 January 2019|archive-url=https://web.archive.org/web/20160304204132/http://www.bladmineerders.nl/minersf/lepidopteramin/euspilapteryx/auroguttella/auroguttella.htm|archive-date=4 March 2016|url-status=dead}}</ref><ref name="Practical">{{cite book |last1=Shield |first1=Richard |title=Practical Hints Respecting Moths and Butterflies, With Notices of Their Localities : Forming a Calendar of Entomological Operations Throughout the Year, in Pursuit of Lepidoptera |date=1856 |publisher=John Van Voorst |location=London |pages=7, 42, 59, 83, 101 |url=https://archive.org/details/practicalhintsre00shie/page/7 |access-date=10 August 2023}}</ref> ''[[Agonopterix hypericella]]'' is another small ({{convert|17|mm|abbr=on}}) gray moth that exclusively feeds upon ''Hypericum''.<ref>{{cite web |title=Agonopterix hypericella (Insecta: Lepidoptera: Depressariidae) |url=http://www2.nrm.se/en/svenska_fjarilar/a/agonopterix_hypericella.html |website=Svenska Fjärilar |publisher=Naturhistoriska Riksmuseet |access-date=10 August 2023}}</ref><ref name="Practical" />

''Zeuxidiplosis giardi'', the common St. Johnswort gall [[midge]], is a small ({{convert|3|mm|abbr=on}}) fly that eats ''H. perforatum'' while developing. The larvae feed upon leaf buds, which causes the plant to form a round growth called a [[gall]] where the developing insect can feed, is protected, and [[pupa]]tes into a mature adult.<ref name="FSControl" />

=== Toxicity ===
''Hypericum perforatum'' is [[Toxicity|toxic]] to numerous domestic animals such as cows, sheep, and horses. When these animals come into contact with the plant, usually through grazing, they develop serious symptoms. The first signs are reddening of the skin accompanied by swelling, which is followed by [[necrosis]] and [[Skin sloughing|sloughing]] of the skin. Non-[[Biological pigment|pigmented]], white skin is most affected by the poisoning, such as the nose and ears of certain breeds of sheep.<ref name="Colostate">{{Cite web |title=Guide to Poisonous Plants – College of Veterinary Medicine and Biomedical Sciences – Colorado State University |url=https://poisonousplants.cvmbs.colostate.edu/Plants/Details/43 |access-date=2023-09-23 |website=poisonousplants.cvmbs.colostate.edu}}</ref> Young animals are more susceptible to ''H. perforatum'' poisoning, and the plant is most toxic in spring (when it is the most palatable to herbivores) and retains its toxic effects when dried in [[hay]].<ref>{{Cite book |url=https://www.nwcb.wa.gov/pdfs/Final-WSNWCB-toxic-booklet_low_res.pdf |title=Protect Your Horses and Livestock From Toxic Plants |publisher=Washington State Noxious Weed Control Board |year=2017 |pages=49}}</ref> Additionally, affected animals will become highly [[Photosensitivity|photosensitive]], and exposure to sunlight can exacerbate their symptoms. As such, they should be moved to a dark area; administering of [[antihistamine]]s or [[anti-inflammatory]] medicines may also help alleviate the symptoms.<ref name="Colostate" />

=== Invasiveness ===
[[File:Hypericum perforatum field belair park.jpg|thumb|''Hypericum perforatum'' growing prolifically in [[Belair National Park]], [[South Australia]]]]
Although ''H. perforatum'' is grown commercially in some regions of southeast Europe, it is listed as a [[noxious weed]] in more than 20 countries and has introduced populations in South and North America, India, New Zealand, Australia, and South Africa.<ref name="cabi" /><ref name="feis">{{cite web | url = http://www.invasive.org/weedcd/pdfs/feis/Hypericumperforatum.pdf | work = Fire Effects Information System | title = SPECIES: Hypericum perforatum }}</ref> In pastures, St John's wort acts as both a toxic and invasive weed. It replaces [[native plant|native]] [[plant community|plant communities]] and [[forage]] vegetation to the extent of making productive land nonviable or becoming an invasive species in natural [[habitat]]s and [[ecosystem]]s.<ref name="North West Weeds">{{cite web|title=St John's wort – Hypericum perforatum|url=http://www.northwestweeds.com.au/sample-page/st-johns-wort-hypericum-perforatum/|url-status=dead|archive-url=https://web.archive.org/web/20160331070345/http://www.northwestweeds.com.au/sample-page/st-johns-wort-hypericum-perforatum/|archive-date=31 March 2016|access-date=2015-10-19|website=North West Weeds}}</ref>

Effective herbicides for control of ''Hypericum perforatum'' include [[2,4-Dichlorophenoxyacetic acid|2,4-D]], [[picloram]], [[Metsulfuron-methyl|metsulfuron]], and [[glyphosate]].<ref name="FSControl" /> Insect herbivores have also been introduced as [[biocontrol]] agents in areas outside their native range. Some of the most widely used are ''Chrysolina quadrigemina'', ''Chrysolina hyperici'', ''Agrilus hyperici'', ''[[Aplocera plagiata]]'', and ''Zeuxidiplosis giardi''.<ref name="FSControl" /><ref name="Harper2010">{{cite book |last1=Harper |first1=John L. |title=Population Biology of Plants |date=2010 |publisher=Blackburn Press |isbn=978-1-932846-24-9 }}{{page needed|date=September 2021}}</ref>