Tnx Rich,
as using Thea for rendering then just (for testing) made really simple model of tree trunk as Instance base & used "ring" model as instance & basically that's it. Probably have to play with thickness of instances & have to create a better base model to get the proper shape of tree but otherwise does the job good enough.
My Q was pretty much for the interest if there's an easy way to do it in SU with any kind of plugins & from the point of getting smarter in SU. You're never too smart in SU, are you?
Will try those suggestions You offered as well just out of curious. Thanks for that
Cheers,
Mark