Horticulture Departments in U.S. universities

University of Arkansas

http://hort.uark.edu/

Cornell University

http://hort.cals.cornell.edu/

University of Wisconsin


http://www.horticulture.wisc.edu/faculty/facultylist.php

Purdue University

http://www.hort.purdue.edu/hort/default.shtml

Washington State University

http://hortla.wsu.edu/

University of Florida

http://hort.ifas.ufl.edu/

Penn State University

http://horticulture.psu.edu/node/386

I believe Ohio State University and Cornell University are among the best, if not the best, in the US.

Most schools with a horticulture program in the States are state-run universities, known usually as Land Grant Universities. Most all of them are good hort schools. But I believe Cornell is a hybrid university, part private and part state-run. The private part has made it one of the highly respected Ivy League colleges, so the name "Cornell University" has quite a cache.

One thing to think about: Decide where you want to work and chose a university that has a matching climate. For example, if you want to work at The Royal Gardens of Jamaica (assuming there is one), don't attend the University of Maine. Rightly or wrongly, potential employers will assume you know nothing about tropical plants.