Bare root trees and shrubs are usually less expensive than containerized or balled and burlapped plants, but are available only during their dormant season, usually in early spring before plants have leafed out.
Containerized and balled and burlapped trees and shrubs are available throughout the growing season. Generally, balled and burlapped plants are larger than containerized plants, although large containers are sometimes available.
This information was obtained from:
Hardgrave, P., Landscaping New Homes, Avon Books, New York, 1992.