I found this tiny Cardamine species near Horseshoe Bay between some boulders which were close to the Upper Levels Highway on May 31, 2006. Is this little western bitter-cress (Cardamine oligosperma) or is it western bitter-cress (Cardamine occidentalis)? I do not believe that there is a third choice but I'd certainly like to read about other suggestions if there are any. The young fruits (siliques) were about 1 mm in diameter, stamina 6 (as far as I can recognize this from the photos). I know that some of the photographs are rather bad (especially the rightmost one) but this is all that I got.
Looks just like the Hairy Bittercress in my garden - could there be naturalised/invasive Cardamine hirsuta in the region?
I suggest that my photographs show neither Cardamine nuttallii (which has simple leaves; my plant had compound leaves) nor Cardamine hirsuta. The latter species has great similarity to my plant in fact but it usually blooms earlier in my place and it is not so hairy at the stem base (in spite of its name) but mostly hairless or with just a few hairs. The number of stamens per flower in Cardamine hirsuta is mostly 4, sometimes 5 but rarely 6 (as in my case here). And C. hirsuta is not mentioned in the "Illustrated Flora of British Columbia". So Cardamine oligosperma or possibly C. occidentalis are still my favourite choices - not numerous species of small-flowered bitter-cress because these do not exist in B. C. as far as I know.
I just found Cardamine hirsuta in the "Illustrated Flora of British Columbia" and it even seems to be common in southern British Columbia. Nevertheless for the reasons I told you already my plant is probably different. It is rather hairy on the leaves, however, which is supposed to be the case only with C. hirsuta. The leave stalks do not appear to be very hairy except for a single one near the ground. Nevertheless I still suppose that this might be C. oligosperma rather than C. hirsuta or C. pensylvanica or C. occidentalis which seem to grow in moister areas. What do you think about this? I added a few more detail photos.
Jacobson, Wild Plants of Greater Seattle lists C. flexuosa ("common") C. hirsuta ("common") C. hirsuta oligosperma ("relatively rare") C. occidentalis ("last collected in 1889") C. pensylvanica ("common") C. pratensis ("common in east-central Seattle") C. pulcherrima tenella ("last collected in 1931") for down here. Mix up there probably fairly similar, at least in lowland settled areas like Vancouver and vicinity.
Hi Ron, thanks for your list of bitter-cress species from the Seattle area! It is really interesting. It might in fact be not so easy to recognize the correct species if you have so little information about some of the species. I already know that my plant is not Cardamine hirsuta s. str. and that Cardamine pratensis and Cardamine pulcherrima can be excluded because of the size of their petals. Cardamine occidentalis is said to be fairly rare, probably not sufficiently weedy and it seems to be a plant of extremely moist places close to streams and lakeshores. So this is very unlikely. One of the problems with C. pensylvanica is that the leaves of this species are supposed to be generally glabrous. And my specimen has some rather hairy leaves. I also suppose that the leaflets at the stem might be usually much longer than wide. Cardamine oligosperma is possible but I cannot recognize any hairy fringes of the leaf-stalks. I also do not know how to count the seeds. I can recognize about 13 of them in one of the fruits (which might be alright only if I need not multiply this number by 2) but I do not know whether it is possible to count them all when you see the fruit just from one side. I am also not sure about Cardamine flexuosa. This is a common wildflower in my place but at least the upper leaves of typical specimens from my area look much more like the images of Cardamine pensylvanica which I found on the web but not at all like my photographs from West Vancouver. Cardamine flexuosa was also excluded from the "Illustrated Flora of British Columbia" because it had been collected only once in B. C.; so it might not be common in the Seattle area either - but possibly the result of confusion with other species. Kind regards, Robert.
Jacobson (Wild Plants) says Pennsylvania bittercress "is a highly variable tetraploid rather than a diploid like HAIRY BITTERCRESS. The leaflets are 7-13 and more elongated. It is more or less hairy. The flowers are larger and a bit showy. Seedpods are notably slender, with more seeds: 20-40."
So does that mean that you suspect that my plant is Cardamine pensylvanica in spite of the slightly hairy leaf blades?
