Before you go to the garden center to make your purchase, identify the planting site. This will determine several factors that influence which trees or shrubs would grow successfully.
Evaluate the existing site conditions, asking yourself several questions. What is the size of the site, large or small? Are there overhead or underground utilities within proximity? Are there sidewalks, driveways, houses or any other structures nearby? Are there any other plantings nearby that can influence tree or shrub selection? What is the garden style, formal or informal, native or non-native? What is the USDA hardiness zone? What is the average annual rainfall? What is the sun, heat and wind exposure? Is there good or poor drainage? Is there a nearby water source? What are the soil conditions? Take a soil test, if necessary.
Trees and shrubs are long-lasting in the landscape, so whatever you decide to do will be an investment in your garden's future. Set high standards when considering your plant needs and wants. Will the tree or shrub require special maintenance or heavy pruning? Are you willing to invest the time needed to do such work? Do you want a plant that attracts wildlife, has seasonal flowers, is low maintenance or provides an evergreen screen? Are there any other characteristics you desire? How much do you want to pay for the plant?
Once you've considered the site conditions and desired plant characteristics, make a list of potential trees or shrubs. Personal preference has major influence on plant selection. Do your research on the internet or in books and magazines. Consult with your local extension service or garden center for recommendations. Weed out plants that don't fit your qualifications. Do a cost benefit analysis, asking yourself, "Will this plant give me the best landscape performance for my money?"
With your plant list in hand, go to your local garden center or search online for your desired plants. Trees and shrubs are sold in three forms: bare root, balled and burlapped and containerized. Bare-root plants are the most economical choice and are best planted in early spring or winter. Balled-and-burlapped and containerized trees and shrubs are more expensive than bare-root plants, but they're available during the peak gardening season. When selecting a balled-and-burlapped plant, make sure the root ball feels firm to the touch.