The flowers pictured here are easily identifiable as a Cardamine species. In the Maryland Piedmont, we have about 10 species of Cardamine, a handful of which have flowers very similar to what’s pictured. We call them “toothwort”, and the various species are readily identified by differences in their leaves.
Not so with this one. Almost as soon as I started trying to identify these I ended up in a taxonomic whirlpool.
A Guide to the Flowering Plants and Ferns of Iceland shows one species with flowers like this, and calls it Cardamine pratensis ssp. angustifolia. The listing Cardamine nymanii in the index goes to the same plant. Are the names synonyms? The book doesn’t say.
The Integrated Taxonomic Information Service accepts both C. pratensis and C. nymanii, but does not accept C. pratensis ssp. angustifolia, which it considers a synonym for C. nymanii.
The Botanical Map of Iceland shows a similar-looking plant and labels it C. nymanni.
The Natural History of Iceland website shows only C. nymanii.
In English one of these is called cuckoo flower, and the other is lady’s smock. Both have the same common name in Icelandic: hrafnaklukka.
I had to go to Svalbard to get an answer. Not literally, of course (I wish!), and only an answer, not the answer. The comments section of the listing for C. pratensis ssp. angustifolia on the svalbardflora.no website says “The Cardamine pratensis group is unusually complicated taxonomically.” It goes into a rather interesting discussion (interesting if you’re into that sort of thing) about the taxonomic difficulties and distribution of the similar species.
But hey, useful ID tips from the same site:
Cardamine nymanii is distinguished by, e.g., the glabrous, entire, fleshy leaflets with impressed veins. In the two others, the leaflets are often hairy, dentate, thin, and with protruding veins. Cardamine nymanii is distinguished from C. pratensisalso by the often distinct petiolules of leaflets on stem leaves (in common with C. dentata but absent from C. pratensis).
Well, guess what? I don’t have good enough pictures of the leaves. The ones I do have definitely show glabrous (smooth), entire (not toothed or lobed), fleshy leaflets, but they don’t have distinct petiolules (leaflet stems).
Gah! So what species did I find? I really can’t say.
Maybe I should just dub them “Icelandic toothwort” and add to the confusion.
Whatever species they end up being, they’re fairly common throughout Iceland, found almost everywhere except in parts of the highlands. I saw them blooming on Mt. Esja and in several places around Ísafjörður in the Westfjords.