Can you post a close-up of the foliage? Kind of hard to tell without one.

I linked it but I guess it would be easier this way

Hey LeaveIt, Yes, thats a 'Seiryu'! The price sure was right!

~AL

Snow or ice would take it out the first winter here, and I'm in Zone 8 also. I can see why it sold so cheap. Narrow crotch, two leaders, small rootball, skinny trunk, and a lot of top growth. Recipe for disaster.
Nice variety though.
Good luck.
Mike

You should consider some selective pruning to improve the tree's form.

Several years back, I had become unhappy with my 'Sieryu'. So I cut it all back down to about a feet above the ground, leaving nothing but trunk. Did it right around this time of year. Then, the following spring, a lot of dormant buds broke right under where I had cut the top off and now I have a nice vase-shaped spreading tree, which is really how this variety looks best anyhow (IMO). The situation was somewhat different from yours since it had already been in the ground a few years and was well established.

Here's a photo, in case of any interest. Not the best shot, but shows the multi-trunk structure that is developing:

-Alex

How should I prune it?

I'd prune nothing now. That tree will need all the leaves it can get for another year or two. When planted, I would take the branch I intended to keep and straighten it as best I could with stakes and/or splints. If it breaks in the process, you'll still have the other one.

tj