There are a number of good yellow, cold hardy, deciduous Magnolias; Sunspire (narrow) and Golden Gift come to mind. and there are others. Look at the offerings of Rare Find Nursery. BUT, magnolias need acid soil. Do you have that in Utah?

I have Magnolia 'Butterflies' growing here in Hamburg, NY near Buffalo. The tree is growing well despite some damage from our "October Surprise" snow storm.

It is supposed to be an upright grower to 18 - 20 feet tall. The flowers are very bright yellow and very numerous once it begins to flower.It is a hybrid of Magnolia accuminata and Magnolia denudata.

Rare Find Nursery carries 2 -3 feet tall specimens for $50.00. I recommend this nursery as I have ordered from them and quite pleased with the tree I bought from them.
www.rarefindnursery.com

Hope this helps ...

'Butterflies' is also the one I was thinking of. Mine has only been through one winter, and not much of a winter at that. I do know of a few in this area that have survived several winters, so it would seem this tree is at least z4b (-25F) hardy. The only other yellow-flowering magnolia I've got is 'Sunsation', which is a fairly recent introduction. I bought it in June, and my concern at the moment is to get it through the blistering heat and drought we've been experiencing. I think its a two-year old graft, and seems to be a bit of a weakling. This tree has large (7" wide), deep yellow flowers with a red/purple base. It has an upright and formal habit and is supposed to be a vigorous grower hardy into z4. We'll see about that!

A number of yellow magnolias have been developed at the Brooklyn Botanic Garden for cold hardiness and late season bloom. One is called 'Elizabeth' but there are several others. Check out Fairweather Gardens, which carries a lot of magnolias.

Here is a link that might be useful: Fairweather

I can't say enough good things about 'Elizabeth,' a proven, hardy yellow magnolia. Below is a link to a thread I started in the Minnesota forum earlier this year

Here is a link that might be useful: 'Elizabeth' discussion in the MN forum

Hi, John. Yes, I forgot all about Elizabeth. Flowers may not be a true yellow, but still a beautiful tree in its own right. There's a mature specimen on the grounds of Funkie Gardens in Prescott, WI, that has ben through some mighty cold weather without significant damage. I need to find a place for one of these.

I think with everything said here, I'm going to go with 'Butterflies'. Thanks so much, everyone, for your responses!

I was found some 'butterflies' here around Boston. What a beautiful tree! I'm going to look for a smaller one, though. The ones I saw were about 9-10' with a huge root ball... I'll look at Rare Find, discussed above. If anyone knows of other places to look, I'd be interested...