Trees are usually defined as perennial woody plants that have one main trunk and many smaller branches that grow out from the trunk at some height above the ground. Shrubs, on the other hand, are usually described as low, woody plants with several stems instead of a single trunk. Though trees are generally taller, some healthy shrubs can tower over dwarf trees. For this reason, the presence of a single trunk or multiple stems is the best way to tell trees from shrubs.

Tree and Shrub Anatomy

• Bark: Bark is the outer layer of a tree trunk and branches that protects the plant from damage and disease. The inner bark is located just underneath the bark and carries the food made by the leaves to the other parts of the plant.
• Bole: The bole is the part of a tree trunk between the ground and where the branches grow. It is often useful for lumber.
• Branches: Branches support the leaves and form the crown of the plant.
• Crown: The crown is the upper part of a tree or shrub that includes the branches and the foliage.
• Heartwood: Heartwood is located at the center of the tree and is the oldest and densest part of the trunk.
• Leaves: Leaves on both trees and shrubs make food for the plant using photosynthesis.
• Limbs: Limbs are live, sound tree branches that have a diameter of at least 4″ next to the trunk.
• Root hairs: These are hairs located on the ends of tree and shrub roots that absorb water and nutrients from the soil.
• Sapwood: Sapwood is located below both layers of bark and carries the water and nutrients from the roots to the leaves.
• Shallow roots: These grow horizontally away from the tree trunk, or shrub stems, just below the surface of the ground.
• Stem: This is the woody, upright part of a shrub that supports the leaves and gives the plant its shape.
• Taproot: This is a single, central tree root that grows straight down into the soil.
• Trunk: The trunk is the central stem of a tree that is covered with bark and extends from the roots to the uppermost branches of the crown.
• Twigs: Twigs are the small shoots that are the current season’s branch or stem growth.

Deciduous vs. Evergreen Trees and Shrubs

Both trees and shrubs may be deciduous or evergreen.

• Deciduous plants: These shed their leaves for part of the year and regrow them for part of the year. Examples include maples, elms, birches, and cherries.
• Evergreen plants: These keep their leaves or needles throughout the entire year. Examples include pines, firs, junipers, and boxwoods.

All trees and shrubs are perennials, meaning that they come back year after year rather than die off after the course of only one or two growing seasons.

Where to Buy Trees and Shrubs

There are generally three main places to shop for trees and shrubs: local nurseries, mail-order catalogs, and the internet.

Local Nurseries

Local nurseries are often the best place to buy trees and shrubs. No plant is a good match for you unless it can survive in your climate, and few people know what will survive in your area better than the people at a local nursery. Good nurseries grow most of the plants they sell, so the plants will most likely be dependable and disease-resistant. It’s still always important to inspect the plants before purchasing them. Avoid buying plants that show any of the following characteristics:

• Yellow leaves
• Spindly plants
• Wilted leaves
• Insect infestations
• Scars on stems or trunks
• Weeds in pots

Mail-Order Catalogs

Mail-order catalogs generally offer an astounding variety of plants, including all kinds of trees and shrubs. However, they don’t offer much firsthand expertise or specific advice about what will grow well in your particular area. For this reason, order only from catalogs that tell a lot about each plant, and read these entries carefully to make sure the plant you’re considering is suitable to your location.

Keep in mind that the trees and shrubs you order will generally arrive in a bare-root, dormant state, ready for planting. Some suppliers also offer these plants in pots of various diameters—a 4″ pot is one common size. The individual product descriptions for each tree or shrub explain how they should be planted. To find some of the popular mail-order retailers, search online for “mail-order gardening catalogs.”

The Internet

If you feel comfortable shopping on the internet, online shopping is a good alternative for finding trees and shrubs. The vast majority of mail-order tree and shrub catalogs have websites as well. Browsing through these websites allows you to select from a wide variety of choices in just a little time.

Trees and shrubs are available from many other internet sources besides the standard catalog retailers. Nonprofits such as the National Arbor Day Foundation (www.arborday.org) sell plants, as do all kinds of specialized suppliers. As with mail-order catalogs, internet vendors don’t always offer the same specific expertise and advice that local nurseries can provide, but the variety and selection online is unmatched.