| Hypericum kalmianum | |
|---|---|
 | |
| In cultivation | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Malpighiales |
| Family: | Hypericaceae |
| Genus: | Hypericum |
| Section: | H.sect. Myriandra |
| Subsection: | H.subsect. Centrosperma |
| Species: | H. kalmianum |
| Binomial name | |
| Hypericum kalmianum | |
| Synonyms[1] | |
Norysca kalmiana(L.) K. Koch | |
Hypericum kalmianum, commonly calledKalm's St. Johns wort[2] orKalm's St. Johnswort,[3] is aflowering plant in the St. John's wort familyHypericaceae. It is native to theGreat Lakes region in the northern United States and southern Canada.Hypericum kalmianum was named after its discoverer, Swedish botanistPehr Kalm (1715–1779).[2]
Hypericum kalmianum is a slender shrub that grows to a height of 20–60 cm (7.9–23.6 in). Its bark is whitish and papery. It has ascending four-edged branches that bear two-edged branchlets. The crowded bluish-green leaves are linear tooblanceolate and 3–4.5 cm (1.2–1.8 in) long. One to ten yellow flowers are borne on terminal and opencorymbs, with each flower measuring 2–3.5 cm (0.8–1.4 in) wide. The leaf-likesepals are oblong and 5–15 mm (0.2–0.6 in) long. The ovoid capsules typically have fivecarpels andstyles, though they can occasionally bear three, four, or six. The capsules are 7–10 mm (0.3–0.4 in) long and 4–7 mm (0.2–0.3 in) thick.[4]
The plant flowers between June and August.[5]
Formerly included withinHypericum kalmianum is another species firstformally described in 2016,Hypericum swinkianum.[6] Both species are part of thesubsectionHypericum subsect.Centrosperma (H. sect.Myriandra).H. kalmianum can be differentiated fromH. swinkianum by its narrower leaves, flowerheads averaging fewer than 7 flowers, and an affinity toward calcareous rather than acidic habitats.[2][6] Additional species ofMidwesternHypericum closely related to these two may be yet to be described.[6]
Kalm's St. Johnswort is primarily found around the Great Lakes in Ontario, Quebec, Illinois, Indiana, Michigan, New York, Ohio, and Wisconsin.[1] In the Chicago Region, it is a highlyconservative species that occur near Lake Michigan incalcareous sand prairies andmarlypannés, and though rarely seen inland, can be found in prairie fens and mesic prairies.[2] It is classified as anendangered species in Illinois and threatened in Ohio.[3]
