Blue Cohosh - Caulophyllum giganteum - Caulophylle géant

In my meanderings yesterday, I came across a single individual of the species Caulophyllum giganteum which was in bloom. This species and another, Caulophyllum thalictroides, are both colloquially referred to as blue cohosh. Indeed, until relatively recently (20 years ago), the two were treated as a single species. They can be distinguished in a few ways that are relevant to us: the first way, which is most obvious right now, is that C. giganteum blooms about two weeks earlier than C. thalictroides [1]. The flowers are also more obviously blue-tinted and less abundant in C. giganteum, and yellow to greenish and more abundant in C. thalictroides [1]. C. giganteum also has a more restricted range than C. thalictroides (combined range map). The style is long in C. giganteum and short in C. thalictroides [1].

C. giganteum in bloom

Although they are separate species, they have quite a lot of characteristics in common [1]. Both are predominantly insect-pollinated with minimal self-pollination [1], and both are considered a traditional women's herb, which was used to treat labour pains or to induce labour, as an abortefactant, and as a contraceptive; it is believed that these plants contain a compound with estrogenic properties [1], but there is presently insufficient evidence to support its use as a medicinal treatment [1,2], and moreover can be quite dangerous and as such is listed as an herb to avoid without prescription and consultation with a doctor [3], as it can have serious harmful effects both on a woman taking the herb, and potentially on a child in the womb as it is also a suspected teratogen [1]. In short, do not use this herb for self-medication under any circumstances, and if discussing the possibility with a doctor, be aware of the side effects associated with its use.

The conservation status of C. giganteum is secure in Canada [4] and secure in the United States, except in Tennessee, where it is listed as threatened [5], likely due to overexploitation [1] (people harvesting too many of the plants and consequently damaging their ability to sustain their population).

The conservation status of C. thalictroides is secure in Ontario and New Brunswick, unknown in Quebec, and potentially at risk in Manitoba and Nova Scotia, with a country-wide ranking of secure [6]. In the United States, it is secure except in Rhode Island where it is threatened [7], again likely due to overexploitation.

C. giganteum flowers; note the distinctive blue and red tints, and the diagnostic long style