Name: Suzanne/Sue Sebastopol, CA (Zone 9a) Sunset Zone 15
My Vitex (Vitex agnus-castus 'Shoal Creek') is on a single truck, I bought it that way and kept trimming any side shoots. I'll need to get up on a ladder now to trim it back and shape it after this years blooms as I haven't done that in a couple of years.
Read the comments, a tree form is mentioned.
Porkpal, they make beautiful trees, although I think the multi-trunk form is the most attractive, and that seems like the way vitex prefer to grow. They are extremely responsive to shaping and pruning.