Trees and shrubs form the permanent elements that provide the structure around which you plan and plant everything else. Beyond providing aesthetic pleasure, these plants make several practical contributions to your home’s landscape. They separate your yard from everyone else’s, screen private areas of your yard from public view, and block unsightly service areas, such as dumpsters and gas tanks. Plants improve air quality, help prevent soil erosion and storm runoff, and help hold the snow and moisture on your property in arid climates. Trees and shrubs bring a natural element to urban landscapes, giving homes to welcome birds and wildlife and providing them with nuts and berries to eat. Trees and shrubs can also reduce your heating and cooling costs. Foliage deflects and absorbs the rays of the sun and, in return, gives off moisture that cools the air — a valuable resource in cities and around paved areas. Shade on your roof from nearby trees can reduce the temperature in your attic by as much as 40°. Shaded air-conditioning units operate two to four times more efficiently, too. Also, U.S. Forest Service studies show that attractively landscaped homes are worth 5 to 20 percent more than homes without trees and shrubs.

This chapter provides you with the information you need to effectively incorporate trees and shrubs into your landscape design.

Separating The Trees From The Shrubs

Trees and shrubs — often called woody plants — share several characteristics, as well as some anatomical features. For example, trees and shrubs have hardened woody stems and trunks that survive from year to year in favorable environments and increase in diameter as the plant grows. Some shrubs die to the ground each year if you plant them in unsuitable climates, but in their natural range, where they normally grow, their stems endure from one year to the next.

The difference between shrubs and trees can be confusing, but the following guidelines can help you distinguish trees from shrubs:

• Trees: These plants usually have a single main stem that gets thicker with age and develops large secondary branches and limbs. Some trees appear to have more than one trunk, but often, what you see are actually several trees growing close together in a clump. Trees that have been injured sometimes send up two or more trunks, too, but that isn’t their usual habit.
• Shrubs: By nature, shrubs have lots of woody stems coming from a central growing point under or close to the ground. Shrubs often form a dense tangle of stems called thickets. The stems on a shrub usually don’t grow large side branches — shrubs generally grow to less than 20 feet high. The line between trees and shrubs gets blurred when a tall shrub is pruned so that it has a single trunk.