To decide which trees are best for you, start by considering the points below. Also consult local nursery personnel and look carefully at the trees in your neighborhood to see which ones perform particularly well.
Landscape function. What role do you want a tree to play in your garden? If you're looking for a source of shade, pick a tree with a wide canopy. Deciduous trees will give you shade in summer, then admit the sun after their leaves drop in fall. To block a view from a neighbor's second-story windows straight into your home or garden, choose relatively tall, dense trees and consider combining them with shrubs. If you want a specimen tree for a garden or patio focal point, look for interesting foliage or a striking display of flowers or berries. Fruit trees such as apple, pear, or plum do double duty, giving you delicious fruit as well as lovely form and flowers.
Climate adaptability. Choose trees that will accept your local climate, including both winter lows and any extremes of summer weather, such as baking heat, dryness, or high humidity.
Cultural preferences. Match the needs of trees you choose to the conditions in your garden. Select those that will grow well in the sort of soil you have, with the amount of water they'll receive naturally or that you can provide.
Deciduous versus evergreen. Deciduous trees start their growth with a burst of new leaves or flowers in early spring, then remain in leaf through summer. In autumn, the leaves drop to reveal the bare limbs. In many sorts of deciduous trees, the leaves change color before they fall.
Evergreen trees include both broad-leafed evergreens and conifers (there are a few deciduous conifers as well). Broad-leafed evergreens have the same sort of foliage as deciduous trees; their older leaves may fall intermittently or in one season. Most conifers have leaves that are narrow and needlelike or tiny and scalelike. Because they keep their foliage year-round, both sorts of evergreens serve well as screens and windbreaks.
Growth rate and size. Different trees grow at different rates. Speed (or lack of it) can be a crucial factor if you need a tree to shade a south-facing window or provide privacy: for quick results, select a fast-growing tree. If you're choosing a tree primarily for its beautiful flowers, however, you may be willing to wait a number of years for the tree to mature and begin blooming.
It's important to visualize the ultimate height and spread of any tree you consider. Not only is an overly large tree out of scale in most gardens, it eventually crowds other plants and may have to be removed--an expensive undertaking.
Root system. A tree with a network of greedy surface roots is a poor candidate for planting in your lawn or within the garden, since it will take more than its fair share of water and nutrients. But the same tree may be just right at the garden's fringes or along a country drive. Some trees have surface roots that can lift and crack nearby pavement, making them less-than-ideal choices for a patio, entryway, or parking strip.
Maintenance. If a tree produces a fair amount of litter from falling leaves, flowers, or fruits, it's not a good selection for planting beside a patio, in a lawn, or near a swimming pool; you'd be spending far too much time cleaning up the debris. Such a tree is a better candidate for a background area, where the litter can remain where it falls. In regions with regular high winds or heavy annual snowfall, avoid trees with weak or brittle wood. They can be hazardous to people and property, and you'd probably have to remove broken branches frequently.
Pest and disease problems. Make sure the trees you are considering are not overly susceptible to pests or diseases. Keep in mind that a tree that's trouble-free in one climate may be plagued with problems in other areas.