I know of a couple of suitable ones, but undoubtedly there are many others. To gain some ideas of others to look for, I'd love to hear about the ones you are growing! (And pix would be wonderful if you have them!)
This is one that I like a lot:
Salix x boydii
Have had a couple of these (not in a rock garden, however, but in an acid bed) for many years.
One that is native to the mountains here, Salix reticulata:
I don't grow this one but would like to... since they are willows, I imagine propagating one from cuttings wouldn't be too difficult. This one seems quite variable in size in the wild, depending on conditions - from very small-leaved and prostrate, to about a foot high...
Salix repens is also very variable. This clone - Iona Form - came from Arrowhead Alpines. It has very small leaves, but still barely fits in a trough. This pic was taken the first year of planting. As you can see, the willow and the Scabiosa japonica took great advantage of the new soil. Since then, they have both calmed down and become more demure. The willow is back to have leaves about two-thirds the size in the pic.
This is the tiniest willow I know. Salix serpillyfolia. Leaves are tinier than thyme! I have had it two seasons now and have not seen any catkins on it yet. This is a last year pic, and this year the plant has doubled in size, but still true to form, and less than a quarter inch is height.
Another one... Salix retusa.
Foliage is nice and shiny (though not quite as interesting as the veiny-leaved ones, IMO) - again, it's currently in an acid bed (but I have an idea for an in-ground rock garden, and may later do some transplanting).
Leftwood - thanks for the pics of your specimens! S. serpyllifolia looks especially intriguing - must keep an eye out for that one. Yes, from googling S. repens, it seems it would likely have to be in very lean soil to stay small!
Has boydii bloomed for you yet? So pretty, they say. My friend who moved to Florida had one, but I never saw it in early spring. He gave it to a mutual friend, so I can still go visit it. Such nice pics you have, and that reticulata sure is happy!
With the Iona Form of Salix repens, when it is grown in small 4 inch pots, it's not difficult to keep the leaves at a half inch (1.3cm) long. But put it in a trough, with all that extra soil and no root competition, it's a battle to keep it that dwarf. Salix serpillyfolia seems incredibly tolerant of summer heat and humidity here, compared to most of the small willows. I am having a heck of a time keeping Salix arctica alive that a friend brought back from Baffin Island (go figure). I had another small Salix sp. in the same trough as repens, always to the back (north side) of the container. It just langushed. Not knowing what else I could do, I turned the trough around so it was on the sunny side, and it died almost instantly.
Say, that wonderfully glaucous, icy blue leaved plant in your Salix retusa photo: At first, I thought it might be Salix candida, but I don't see any stipules. Is it a rhododendron?
No, despite being there (in the acid beds) for a very, very long time, I don't recall seeing any of these willows, including S. x boydii, bloom. (The shot of S. reticulata.. or what I assume to be that, maybe mistakenly... is from the wild.) Actually, we are starting to consider the acid beds as having been a not terribly successful experiment, over a few years now- kind of hard to find interesting and suitable plants that do well there. The very low nutrient conditions may be part of it (no fertilizer - just peat - guess I'm a cruel plant master, LOL!). On the other hand, some things are happy - i.e. have never been able to winter or grow Houstonia caerulea elsewhere, and we have possibly the best bed of twinflower that I can claim to have seen in captivity, LOL! Betula apoiensis and bog birch have also done well in there.
The blue plant is bog rosemary (Andromeda polifolia) - it is, unfortunately, that ridiculously fussy 'Blue Ice' variety, cultivated from some southerly bog... although, in the last 2-3 years, ours have done as well as they ever have (less winterkill than usual). We've often commented that we wished we'd gotten some specimens from the local area instead... I'm sure they'd be much tougher plants.
The only rhodo we have in there is R. mucronulatum 'Crater's Edge'... a deciduous one, which, hasn't bloomed either... sigh. (By the way, I'm open to advice... LOL!)
Ah yes, Altagardener - bog rosmary. I should have guessed. Can't figure why your mucranulatum isn't doing well. But I would think you could grow a simple Ramapo rhododendron. I grew Rhododendron shlippenbachii from seed once. An easy germinator in straight peat. (At least that's what I did.) Chipmunks were the cause of their demise when they were still tiny. This season, a mutual friend of ours gave me a little of her much treasured Therorhodian redowskianum seed. However, I must report that, they did germinate, but before I realized it, moss had taken the miniscule plants over. I think this is what I am most sad (or angry) about this season, as it was totally my fault.
What is that gentian that hates lime? Umm, clusii?
Well, the lack of bloom on the rhodo, if not due to the planting conditions, may more likely be due to the buds being killed... again, from our dry winters, lack of snow cover, chinooks, etc.. (We don't protect anything in our yard.) (I should say that the plant itself looks quite nice after it leafs out each year - we're just missing the almost equally-important flower aspect!) We have a 'PJM' rhodo in the ground on which the flower buds are killed some years too, so that would probably make sense.
About the seedlings... yeah, I can usually blame myself for my seed failures too - I sometimes just get tired of fooling around with them, to be honest. If not for my big back log of seeds, I might even consider taking a year off from it... hmmm.
Just attempted to look up Therorhodian redoskianum - could only find one reference... The one sentence that was translated to English said "...and if you want a REAL challenge, try T. redoskianum"... LOL! Wow, you know how to pick 'em!
I'll definitely look into G. clusii, as a possible candidate for the acid beds. I'm also thinking of moving my one surviving Phyllodoce empetriformis to an acid bed... As I mentioned in the troughs thread, one in a trough burned actually quite badly through the winter (and the other was completely killed) - not sure if the acid bed would change that, but perhaps conditions overall would be more to its liking.
Rhododendron redowskianum is a synonym of Therorhodian redowskianum.
It's more widely known by that, but as I understand it, Therorhodian is the correct name.
Phyllodoce, like cassiope, are snow bed species in the wild....they need continuous snow cover to really thrive. We do reasonably well with them but early spring thaws followed by cold will often do them in.
The dwarf Salix I grow are mostly Newfoundland natives including S. candida, S. reticulata, S. vestita, S. uva-ursi, S. glauca and S. jejuna. I am currently rooting S. arctophila I recently collected in Labrador.
