Friday, July 3, 2015

Heal-All - Prunella vulgaris - Herbe du charpentier

I am back home visiting with my parents right now, in the Upper Gatineau. My mother and grandmother asked me to identify a plant which is growing quite abundantly down by the dock, and I am glad that they did, because it was Prunella vulgaris (heal-all, self-heal), a member of the Lamiaceae (mint family).

Prunella vulgaris - whole plant
Prunella vulgaris is native to most of North America [1], though the USDA indicates that it is introduced to parts of Canada (provinces & territories where it is also native) [1]; the Plants of Canada database seems to disagree with this judgement, not indicating anywhere that Prunella vulgaris is considered introduced in parts of Canada [2]. A more detailed reading of the maps indicates that actually the USDA is claiming that Prunella vulgaris var. vulgaris is introduced in most of Canada, but that Prunella vulgaris var. lanceolata is native [1]. So, to see if I could resolve this disagreement I searched the subspecies on the Plants of Canada database but found that though the subspecies are recognized, there is no data and they are referred back to the parent species page [3,4]. For the moment, therefore, no resolution can be made. I will assume that there is some but perhaps insufficient evidence for the claim that Prunella vulgaris var vulgaris is present and introduced in Canada.

Prunella vulgaris inflorescence
If we're speaking purely of the parent species, we see that it is indicated as weedy [1], and has no other special status in the US [1]. It does have special status in parts of Canada, however: it may be at risk in the Yukon and Saskatchewan, and is unassessed in Newfoundland & Labrador [2].

Prunella vulgaris inflorescence
How are we to reconcile such a messy picture? Invasive or potentially invasive in the US, potentially at risk in Canada? Well, it is likely that all of these claims are true. Plants with very broad distributions will tend to have a varied story because of the wide variety of circumstances and conditions that they grow under. It is likely that the plant is weedy and spreads easily; it is also likely that external factors are overcoming that characteristic in the Yukon and in Saskatchewan.

Prunella vulgaris inflorescence
Prunella vulgaris has a long history of use in folk medicine [5,6,7]. There is at present limited evidence for most claims about its medicinal value (I can't find more than one or two in vitro studies to justify any of the claims). That said, the plant is edible and non-toxic so if you feel like giving it a shot there doesn't seem to be any harm in trying (whether or not it is effective is a different question). Given that it's edible, I have given it a taste. It is relatively plain-tasting but contains some undertones common to plants in the Lamiaceae (mint family); I wouldn't go out of my way to eat it as a green, given its relative blandness, but it adds a nice accent to a cup of tea.

Prunella vulgaris developing infructescence
Prunella vulgaris is a source of nectar for bees and butterflies (there was a large bumblebee visiting when I went to identify the plant) [7], and it serves as a larval host for Colias philodice (the clouded sulphur butterfly) [7], which is a common little North American butterfly.

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