{{Short description|Species of flowering plant in the St John's wort family}} {{Speciesbox | image = | image_caption = | genus = Hypericum | display_parents = 2 | parent = Hypericum sect. Trigynobrathys | species = harperi | authority = R.Keller | synonyms = *''H. denticulatum'' var. ''acutifolium'' <small>Fern. & B.G.Schubert</small> | synonyms_ref = }}

'''''Hypericum harperi''''', the '''sharplobe St. Johnswort''' or '''Harper's St. John's wort''', is a perennial flowering plant in the family Hypericaceae. It is an aquatic herb native to southeast North America. ''H.&nbsp;harperi'' has a diploid chromosome number of 24.

==Taxonomy==

Webb, in his dissertation, referred to ''H.&nbsp;incertum'' as the cypress pond St. John's wort. When Steudel transferred the species of ''Brathys'' to ''Hypericum'', he created the nom. nov. for ''Brathys lanceolata'' due to the name ''H.&nbsp;lanceolatum'' already existing for an Old World species. After finishing his dissertation, Webb annotated the type of ''B.&nbsp;lanceolata''/''H.&nbsp;incertum'' and henceforth used the name ''H.&nbsp;harperi''.<ref name=synopsis/>

Though similar to ''H.&nbsp;denticulatum'' var. ''acutifolium'' (and previously identified as that variety), ''H.&nbsp;harperi'' remains distinct in its aquatic habitat and related aerenchymatous stem base. In addition to morphological differences, ''H.&nbsp;harperi'' contains C-glycosyl flavones which var. ''acutifolium'' lacks.<ref name=Bulletin/> No other species of this ''H.&nbsp;denticulatum'' complex has the extensive rhizomes of ''H.&nbsp;harperi'', a specialization indicative of its aquatic habitat and an adaptation shared with its coinhabitants ''Rhynchospora careyana'', ''Oxypolis canbyi'', and ''Lobelia boykinii''.<ref name=synopsis/>

==Description==

''Hypericum harperi'' is a rhizomatous herb with slender, pinkish rhizomes, with a branched base growing {{convert|0.3-1|m|abbr=on}} tall. The flowering branches are typically from median or upper stem nodes. The brown to reddish aerial stems are spongy and become green upward. The green primary stems have four lines and are covered with glandular dots. The internodes are {{convert|8-20|mm|abbr=on}} long, about as long as the leaves. The sessile leaves are ascending and become deflexed when fading. The leaves are {{convert|10-30|mm|abbr=on}} long and {{convert|3-5|mm|abbr=on}} wide. The lanceolate leaves have a plane margin with an acute apex and a cuneate base. There are one to three basal veins and a midrib either unbranched or possessing a single branch. The laminar glands are dense but inconspicuous. The inflorescence possess up to about 30 flowers with flowering branches up to 16 lower nodes. The whole inflorescence is a pyramidal to subcorymbiform shape. The pedicels are {{convert|1.5-2|mm|abbr=on}} long; the bracts are {{convert|2-6|mm|abbr=on}} long. The star-shaped flowers are {{convert|4-10|mm|abbr=on}} in diameter, with orange-yellow petals that number about twice the sepals. The sepals are {{convert|3-5|mm|abbr=on}} long, with three to five veins. The sepals are typically unequal, lanceolate, and have linear glands that become punctiform distally. The 50 to 80 stamens are about {{convert|3-6|mm|abbr=on}} long. The ovoid ovary is {{convert|1-1.5|mm|abbr=on}} long with two to three styles ranging {{convert|2-4|mm|abbr=on}} long. The seeds are {{convert|0.5|mm|abbr=on}} long.<ref name=Bulletin>{{cite book |url= https://www.biodiversitylibrary.org/item/19494#page/69/mode/1up |pages= 67–68 |title= Studies in the genus Hypericum L. (Guttiferae) 8. Sections 29. Brathys (part 2) and 30. Trigynobrathys |series= Bulletin of the British Museum (Natural History). |volume= 1 |publisher= British Museum (Natural History) |author= Norman K. B. Robson |year= 1951}}</ref>

==Habitat and distribution==

''Hypericum harperi'' grows in swamps as well as wet pine barrens, especially the shallows of depressional wetlands (Carolina bays). It rarely will occur in open, seasonal depressions. It grows in the coastal plain of South Carolina, Georgia, and northern Florida.<ref name=Bulletin/> It occurs at elevations between {{convert|0-200|m|abbr=on}}.<ref name=eflora>{{cite web |url= http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250100873 |access-date= October 2, 2018 |website= Flora of North America |publisher= eFloras.org |title= Hypericum harperi}}</ref> It occurs alongside ''Taxodium ascendens'', ''Nyssa biflora'', and other similar species.<ref name=synopsis>{{cite journal |issn= 1938-4386 |url= http://www.jstor.org/stable/41301584 |author= James R. Allison |journal= Castanea |number= 1 |pages= 99–115 |publisher= Southern Appalachian Botanical Society |title= Synopsis of the Hypericum denticulatum Complex (Hypericaceae) |volume= 76 |year= 2011|doi= 10.2179/10-009.1 |jstor= 41301584 |s2cid= 85648010 |url-access= subscription }}</ref>

==References== {{Reflist}}

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harperi Category:Plants described in 1923