Hypericum

Hypericum olympicum, photographed by Michael Kesl.

Belongs within: Malpighiales.

Hypericum, the St John's worts, is a cosmopolitan genus of yellow-flowered plants, varying from herbs to small trees. The common St John's wort or klamathweed Hypericum perforatum has been used pharmaceutically though it may cause adverse reactions, especially in combination with other drugs. It is considered a noxious weed in many parts of the world and may poison livestock.

Characters (from Li & Robson): Shrubs, subshrubs, or perennial herbs (rarely trees), glabrous or with simple hairs, with translucent ("pale") and often opaque, black or reddish ("dark") glands, laminar (immersed and sometimes abaxial) and marginal or intramarginal. Leaves opposite (occasionally whorled), sessile or short petiolate, venation pinnate to palmate (or rarely dichotomous), margin entire or gland-fringed. Inflorescence cymose. Flowers bisexual, homostylous (occasionally heterostylous), stellate or cupped. Sepals 5 and quincuncial or rarely 4 and decussate, unequal or equal, free or partly united. Petals (4 or)5, contorted, golden to lemon yellow (or rarely white), abaxially sometimes tinged or veined red, persistent or deciduous after anthesis, usually asymmetric. Stamens in (4 or) 5 fascicles, free and antipetalous, or some united to form apparently 4 or 3 fascicles with compound fascicle(s) antisepalous, or irregular and apparently not fasciculate, persistent or deciduous, each single fascicle with up to 70(-120) stamens; filaments slender, free from nearly base (occasionally to 2/3 united) or apparently completely free; anthers small, dorsifixed or ± basifixed, dehiscing longitudinally, with gland on connective; sterile fascicles (fasciclodes) absent [very rare]. Ovary 3-5-loculed with axile placentae or ± completely 1-loculed with (2 or)3(-5) parietal placentae, each placenta with (2 or) few to many ovules; styles (2 or)3-5, free or partly to completely united, more or less slender; stigmas small or more or less capitate. Fruit a septicidal capsule or rarely ± indehiscent, valves often with oil-containing vittae or vesicles. Seeds small, often carinate or narrowly unilaterally winged; testa variously sculptured, not arillate (very rarely carunculate); embryo slender, straight, with distinct slender cotyledons.

<==Hypericum Linnaeus 1753 A61
    |--H. anagalloides H93
    |--H. androsaemum H90
    |--H. annulatum V09
    |--H. beanii CB01
    |--H. brachyphyllum M83
    |--H. calycinum CB01
    |--H. canariense CB01
    |--H. concinnum H93
    |--H. formosum H93
    |    |--H. f. var. formosum H93
    |    `--H. f. var. scouleri H93
    |--H. fraseri XR12
    |--H. fuertesii J87
    |--H. gramineum Forster 1786 (see below for synonymy) A61
    |--H. hidcote CB01
    |--H. hirsutum CB01
    |--H. humifusum C06
    |--H. hypericoides J87
    |--H. japonicum Thunb. 1784 (see below for synonymy) A61
    |--H. kalmianum XR12
    |--H. kouytchense CB01
    |--H. lalandii Choisy in DC. 1824 A61
    |--H. millefolium J87
    |--H. monanthemum O88
    |--H. × moserianum [H. calycinum × H. patulum] H90
    |--H. mutilum H93
    |--H. olympicum CB01
    |--H. patulum CB01
    |--H. perforatum XR12
    |    |--H. p. var. perforatum CB01
    |    `--H. p. var. angustifolium CB01
    |--H. pulchrum CB01
    |--H. quadrangulum CB01
    |--H. quinquenervium C55b
    |--H. reptans CB01
    |--H. revolutum B06
    |--H. richeri C55a
    |--H. rowallene CB01
    |--H. russeggeri S54
    |--H. stellatum CB01
    `--H. tetrapterum CB01

Hypericum gramineum Forster 1786 [=Sarothra graminea (Forster) Kimura in Nakai & Honda 1951; incl. Brathys forsteri Spach 1836] A61

Hypericum japonicum Thunb. 1784 [=Sarothra japonica (Thunb.) Kimura in Nakai & Honda 1951; incl. H. pusillum Choisy 1821] A61

*Type species of generic name indicated

REFERENCES

[A61] Allan, H. H. 1961. Flora of New Zealand vol. 1. Indigenous Tracheophyta: Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledones. R. E. Owen, Government Printer: Wellington (New Zealand).

[B06] Burgoyne, P. M. 2006. Review: Plants of the Simen. A flora of the Simen Mountains and surroundings, northern Ethiopia. Bothalia 36 (2): 253.

[C55a] Candolle, A. de. 1855a. Géographie Botanique Raisonée: Ou exposition des faits principaux et des lois concernant la distribution géographique des plantes de l’époque actuelle vol. 1. Librairie de Victor Masson: Paris.

[C55b] Candolle, A. de. 1855b. Géographie Botanique Raisonée: Ou exposition des faits principaux et des lois concernant la distribution géographique des plantes de l’époque actuelle vol. 2. Librairie de Victor Masson: Paris.

[C06] Cheeseman, T. F. 1906. Manual of the New Zealand Flora. John Mackay, Government Printer: Wellington.

[CB01] Cullen, J. M., & D. T. Briese. 2001. Host plant susceptibility to eriophyid mites used for weed biological control. In: Halliday, R. B., D. E. Walter, H. C. Proctor, R. A. Norton & M. J. Colloff (eds) Acarology: Proceedings of the 10^th International Congress pp. 342–348. CSIRO Publishing: Melbourne.

[H90] Harden, G. J. (ed.) 1990. Flora of New South Wales vol. 1. New South Wales University Press.

[H93] Hickman, J. C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press: Berkeley (California).

[J87] Judd, W. S. 1987. Floristic study of Morne La Visite and Pic Macaya National Parks, Haiti. Bulletin of the Florida State Museum—Biological Sciences 32 (1): 1–136.

[M83] Myers, R. L. 1983. Site susceptibility to invasion by the exotic tree Melaleuca quinquenervia in southern Florida. Journal of Applied Ecology 20: 645–658.

[O88] Ohba, H. 1988. The alpine flora of the Nepal Himalayas: an introductory note. In: Ohba, H., & S. B. Malla (eds) The Himalayan Plants vol. 1. The University Museum, University of Tokyo, Bulletin 31: 19–46.

[S54] Seidenstücker, G. 1954. Cyphodema rubricum n. sp., eine neue Mirine aus Syrien (Ins. Hem. Het. Miridae). Senckenbergiana Biologica 35: 99–100.

[V09] Verdcourt, B. (ed.) 2009. Additions to the wild fauna and flora of the Royal Botanic Gardens, Kew. XXVI. Miscellaneous records. Kew Bulletin 64 (1): 183–194.

[XR12] Xi, Z., B. R. Ruhfel, H. Schaefer, A. M. Amorim, M. Sugumaran, K. J. Wurdack, P. K. Endress, M. L. Matthews, P. F. Stevens, S. Mathews & C. C. Davis. 2012. Phylogenomics and a posteriori data partitioning resolve the Cretaceous angiosperm radiation Malpighiales. Proceedings of the National Academy of Sciences of the USA 109 (43): 17519–17524.

Last updated: 24 April 2021.