Dryas integrifolia

Submitted by cohan on Mon, 11/12/2012 - 11:49

I was unsure whether to separate this topic from octopetala -where we were talking about this species as well, or piggy-back- if anyone thinks it should be joined they can do so :)

I mentioned that I have seen (if I've id'd correctly!) 3 species of Dryas- drummondii- which is clearly distinct with yellow nodding flowers- octopetala and integrifolia- superficially similar white flowered species- growing in close proximity in the Rockies West/South of here. (I'll dig for some of those pics soon).

Here is what I believe to be D integrifolia (I'll find more pics of this too- just a quick first post before work today) at a site beside Abraham Lake, in the Kootenay Plains region. The plains are considered montane, and are not at a very high altitude- roughly 1100 to maybe 1300 m. This particular site is at the foot of a mountain which reaches down to the man-made lake, and while again not very high, has some alpine plants not seen on the plains generally- presumably the plants are also growing higher up on these mountains, and are able to colonise this lower habitat in open exposed rocky areas.
Note the very small, less toothed (integrifolia suggesting 'whole' as in untoothed, though there are still some teeth, but fewer and less visible than on octopetala)and recurved leaves. These plants are very small, and at this site at least, the patches are not large, maybe a foot or so across..


Submitted by cohan on Mon, 11/12/2012 - 12:11

A couple more shots -this time from the Columbia Icefields (Athabasca Glacier) site- see the octopetala thread as well; These I am not 100% sure of- in person it's easier to tell the difference between the two species- octopetala is larger- in photos without comparison its harder to be sure what I photographed! also I'm not sure if any at this site are hybrids.. the first shot is such a plant- integrifolia or octopetala with slightly recurved leaves?
second shot with Hedysarum boreale

last 2 views, poor shots, but showing some growing habit, among rocks..

Submitted by Lori S. on Mon, 11/12/2012 - 12:15

Hi, Cohan,
Thanks for starting this new species topic!  I would think too that the photos you've posted in the first set are D. integrifolia... although it would be great if an expert could chime in and confirm it.  

A couple of the ones in the second set are a little too small to examine really closely.  This reminds me that I should probably go back yet again through all of my white-flowered Dryas photos... I think I have a lot of somewhat intermediate forms that may or may not be hybrids!  Needless to say, I'm not sure where the tipping point is between variability within a species and what might be a hybrid.  ???

Flora of Alberta says:
D. integrifolia:   "leaf-blades lanceolate-oblong, 0.8-1.5cm long, broadest below the middle, the margins entire or with a few teeth in the lower half and usually somewhat revolute; the base cordate or truncate, the upper surface usually glabrous and not rugose, the lower surface thinly white-tomentose, the non-prominent midvein lacking glandular-stipitate dark hairs".

D. octopetala: "leaf-blades oblong-ovate, 0.8-2.5cm long, the margins coarsely incised-crenate and somewhat revolute, the base subcordate or rarely truncate, obtuse at apex, the upper surface strongly rugose, with wart-like excrescences or merely glandular-viscid, the lower surface white-tomentose between the prominent veins; the veins, also the petioles and stipules, covered with yellowish brown glands".

NB:  Here's a mini glossary paraphrased from Flora of Alberta:
entire: with smooth margins, e.g. a leaf that is not toothed, cleft or lobed
revolute: rolled downward from the margins or apex; in this case, the leaves are rolled under along the edges
cordate: heart-shaped with the point upward
truncate: with the base straight or nearly so, as if cut off
tomentose: covered with short hairs that are matted
rugose: wrinkled

Flora of Alberta also says that the two species hybridize to form "plants with leaves smooth and shiny above but the margins crenate-serrate".

Here's a close-up of one that I thought was D. integrifolia, from Forgetmenot Ridge, where large mats of it are interspersed with mats of D. octopetala... (and I would imagine there would be the potential for many hybrids there):

Submitted by cohan on Mon, 11/12/2012 - 23:56

Thanks, Lori- if the two species are known to hybridise, then I imagine in these sites where both are present (do they also cross with drummondii? and if so, what would those look like??) it must be hard to be sure of some plants, since most of the characters are the same at some point in their variability;
Since both can be somewhat revolute, I wonder how reliable that is as a character? Though it seems integrifolia is generally more revolute?
Certainly the smoothness of integrifolia and roughness/wrinkledness of octopetala seems important. I think there is at least one photo I posted in the octopetala thread that shows leaves clearly not revolute and clearly rugose. I wouldn't be too surprised if many of the others were hybrids..

Here (well, not here, but say on Loveland Pass), Dryas octopetala is a plant found on the leeward side of mountain passes, so covered by snow all winter. True in Canada, too? 

Every time I've tried to grow it (a plant rated to Zone 1) it dried to a crisp during a chinook. Now that snow cover seems to be not only reliable but endless here, I wonder if I should try it again. Beautiful plant.