I buy all my trees at Beaver Dam Nursery, (I've built 3 new homes in the past 5 years, so I do alot of landscaping and am very passionate about it.) It's small and has great quality stock of all kinds, not just trees. If you need help, just talk to Dan the owner and he'll answer any question you have - he's a little nutty but very knowledgeable.
They are about 5 minutes east of Okotoks.
http://maps.google.ca/?ie=UTF8&ll=50...0363&z=16&om=1