hardy Saxifrage for zone 2b

Hi, Krish!  How nice to see you posting!  And from the homeland too...  I am originally from the Saskatoon area - Humboldt.
Welcome!  Oops, sorry, I'd best explain - this is not Malcolm.  It's Lori.   :)   Malcolm is the world-renowned expert on Saxifraga, as I'm sure you are aware.  I am only piping in because I may be able to lend some insight, or reassurance, about growing alpines in the zones that are imagined by the rest of the world to be the ungardenable arctic hinterlands!!  ;)

Rest assured that the hardiness of alpine species*, and plant species in general, is often greatly underrated.   (*Underrating the hardiness of alpine species is especially puzzling to me, given that these things live in some of the cruelest conditions on the planet.)  Providing appropriate conditions is actually what's important, for the most part.  While your mossy saxifrages can likely survive planting in regular garden soil there, your new acquisition will benefit from excellent drainage, even in your relatively low-rainfall area - a specially constructed alpine bed, with a sharply-draining substrate, or a trough filled with same, would be recommended.  As you are getting 'Riverslea' from Wrightman's, it will likely be rooted into a tufa chunk. (Yes? No?)  If this is your first venture into alpines (?) and do not yet have alpine beds, a trough might well be a good way to start out.  You can see examples of troughs, and advice on how to construct them, on the NARGS main site... or you may be able to buy one, if any business is selling them there.  

As to what you will find hardy there, I'm afraid I can make no guarantees, as I only lived there during my pre-gardening years... and that was back in the Jurassic, when there weren't that many land plants anyway.  However, I do garden in Zone 3, Calgary.  We don't get the sustained cold periods that you do there, but that is likely compensated for by the snow cover that you usually do get (unlike here, where snow cover is normally intermittent and fleeting).  Anyway, do have a look at the NARGS photo gallery where I have posted photos of many of the alpine and alpine-ish plants that I grow here.  It may be helpful.  

Krish

Glad you got to post your question. Lori is quite right that the many alpines are incredibly hardy - a great virtue in your zone. In the really high mountains plants (including saxifrages) can be covered with snow for up to 7 or 8 months a year - so a very short growing season. But the key thing is that they do get a proper demarcation between winter and summer - once spring comes and the snow melts it is set fair through till fall. And being further north means you get wonderful long days in summer so they get lots of light - in the very high mountains such as the Himalayas the days are much shorter but since they are much higher up they get extra ultra-violet.

I don't have any experience of growing in such cold conditions (although I've visited Calgary and seen the great saxifrages people manage to grow there) but lots of saxifrages do. Many of the Himalayan species will cope with extreme cold but they would usually be covered with snow - as I presume you will be in winter. And many of the Porphryion (Kabschia) hybrids have Himalayan species in the parentage - 'Riverslea' for example has one Himalayan species (Sax. lilacina) and one European species (Sax. stribrnyi). Many of this type of saxifrage grown by Harvey Wrightman have originated in the Czech Republic and they have cold winters (much colder than England although maybe not as cold as you). One of my hybrids that only Harvey has in North America is 'Honeybunch' which is a cross between S. meeboldii and S. poluniniana (both from the Himalayas) and one of the only yellow-flowered hybrids with purely Himalayan ancestry. The flowers also have a faint sweet scent on warm days (from S. meeboldii which is the only species which seems to have this characteristic although not in every form unfortunately). Another in Harvey's list that is very dramatic is 'Ben Loyal' although I don't know how well that would cope - perhaps ask Harvey himself.

I also think it would be worth considering trying some of the Trachyphyllum saxifrages - usually you have to grow them from seed (such as Sax. funstonii from Alaska, or some of the forms of S. bronchialis - try to get ones that originate in Alaska rather than the Cascades though).

Although you say "not the hybrid mossy saxifrages" it is worth mentionign that the very best collection of these is in Tromso in northern Norway. Well north of the Arctic Circle although down by the coast but I think that their plants will be snow-covered all winter and pictures show them as spectacular in summer.

Hope this helps and maybe you'll get some other views from far northern gardeners.

best wishes
malcolm

.... and while I think of it two Canadian natives that would be worth trying if you can get them are S. oppositifolia - beautiful in nearly all its forms - and S. aizoides - which I've seen in the mountains north of Calgary growing in running water ...

Lori and Malcolm
thanks for the reply. My knowledge of the alpine garden is very little . I was hooked up with this type of gardening after one of those gardening tours arranged by  the perennial society. Once I joined the NARGS I got more information. In fact  Lori ,you are  my  "Guru" in alpine gardening. I looked at the plants you are growing and then I ordered the Saxifrage riverslea. I also ordered from the NARGS seed list based on the list of plants from your garden. It really is fun to grow from seeds. Hope  I can grow some beautiful alpines in my backyard. I am following both of your advice about growing saxifrage.
Krish

Guru??  :o  Yikes, the pressure!  Whew, hope I don't mess up!    ;)
It's good to hear that the local gardening society includes some rock gardeners - a source of local information can be very helpful.  
Bear in mind that I have only scratched the surface of what will grow here (there are much more experienced alpine gardeners here growing a great deal more... and I wish they would join in!) but I hope it gives you some idea of what you  may find hardy in similarly cold or colder zones, and that it provides some encouragement.  Persevering a bit to figuring out the methods that work for you will be the most important thing.    
Another extremely hardy saxifrage that comes to mind is Saxifraga sancta... not so showy as many, but indestructible.  The old one in a trough out front is showing buds right now.
Anyway, all the best with it!

Lori no pressure from my side . Yes the only way I can get instant easy information is through the net.  I got the S.oppostifolia seeds from NARGS seed list and  sowed it outside. I may order some Kabschia group ,rooted in tufa  from wrightman. I have a small alpine bed planted mostly with semps.
krish

If you can keep semps going outside then you should be able to keep saxifrages going. I would expect sempervivums to be less cold hardy than the bulk of saxifrages.

Having another look at Harvey Wrightman's list I would pick:

Saxifraga sp. Betscho Pass since that should definitely be hardy enough
and
Saxifraga 'Elizabeth Sinclair' since that is one of Lincoln Foster's hybrids

Have fun

I just mention this as an interesting (I think) aside... sempervivums are very easily grown across the Canadian prairies in regular clay garden soil, with no enhanced drainage, and are extremely hardy.  (I can't recall, from other non-alpine cold zone forums, hearing of anyone complaining of losing any!  Rock solid hardy through zone 2, and likely even colder.)  I suspect, if they are thought to be less than extremely hardy elsewhere, it may be conditions (i.e. wet) that are at blame... ?
By contrast, the saxifrages in discussion here will require some special conditions, i.e. drainage, as compared to the absolute neglect under which semps will thrive.

I quite agree that saxifrages will require extra drainage but I'm really interested that Sempervivums cope so well - interesting.