I don't have it growing in my garden so I can't comment from personal experience. This is what I found when I Googled it:

http://www.clemson.edu/cafls/demo/plant_profiles/amsonia-tabernaemontana-eastern-blue-star.html

I have had a clump of it for almost 20 years in a quite moist location. It has been a 3x3foot specimen for the past decade or longer. No problems with it growing larger than that, and it has never self-seeded. Really nice plant, and fall color (yellow) is pretty. Enjoy!

None of the Amsonia I grow have spread by roots/suckering, though a mature plant is a big clump. I get occasional seedlings, but not many.

While you make up your mind, I would throw some dirt on the roots or the plant won't survive so it will be a moot point.

Yes, why on earth are you torturing it long term by leaving it bareroot?

Thanks for all you comments. I have an Arkansas Blue Star, so it sounds as if will behave similarly.

After being handed such a massive, mangled root, I wasn't sure what it would do. I'm not trying to torture it, but we had over 30 other perennials to plant and they had to come first. Also, I wasn't sure it wasn't already dead when I got the roots. It is in the shade and watered daily. Now that something is showing green and I know it is viable, it will be planted with loving care.