It is a yellow-flowering annual or perennial herb native to North America and introduced to Ireland and The Netherlands.

Hypericum canadense is a perennial herb that grows in short basal offshoots that are produced in autumn.

The five-veined yellow petals are oblong to oblanceolate and have rounded tips, measuring about as long as the sepals or shorter.

The light brown and cylindrical seeds have conical or rounded ends, measuring 0.6 mm long.

These hybrids can be recognized as Hypericum × dissimulatum as they match material described by Eugene P. Bicknell from Nantucket.

In typical H. canadense, the petals have a rounded or subtruncate apex, reflex only towards the end of flowering, lack any red tinge, and have exceedingly obscure nerves.

The distinctness in reflexing and color of petals is mostly lost in drying, and as such the variety is easily distinguishable in the field but difficult to make out in an herbarium.

H. canadense was first discovered in Ireland in 1954, with a single plant being found on the shore of Lough Mask.

In 1968, the plant was discovered in Ireland again, this time 200 km (120 mi) south of Lough Mask in Glengarriff.

Second, the plant could have been transported to Ireland by natural means, most likely being carried on the feet of the Greenland white-fronted goose if by any bird.

The plant's occurrence in Newfoundland gives credence to its hardiness, suggesting that it could have withstood the latest glaciation.

The attempted creation of the Corrib-Mask Canal lowered water levels in the herb's Irish area, and if the plant was underwater before then, the relict hypothesis would be disproven.

The majority of evidence is in favor of the relict hypothesis, but future spreading or lack thereof of the plant will better suggest recent introduction or the growth of an autochthon.

[11][12] Hypericum canadense occurs in wet or dry soils in sandy ditches and clearings, road verges, pastures, boggy or peaty regions, gravelly beaches, and occasionally in woodlands.

[8] In Ireland, the herb occurs in wet soils of pH between 4 and 5, with rich organic matter.