A good windbreak should technically be at least 3 rows. You want a tall tree, a medium tree and a shrub. Both height and density matter. This link to the University of Missouri Extension website will help explain:
http://extension.missouri.edu/xplor/agguides/forestry/g05900.htm
(note you can download a pdf copy of the guide for offline viewing by clicking the link in the left hand margin)


Your tree selections may need to be different based on climate, but the idea is still the same.

Good luck!

12 ac pond in NW Missouri. 28' max depth at full pool. Fish Present: LMB, BG, RES, YP, CC, WB, HSB, WE, BCP, WCP, GSH.