Trees — they aren’t just for forests anymore. Experts advocate growing more trees in cities at a time when development, disease and public debt are all leading to fewer trees in urban areas. Many homes are spreading to larger portions of their lots, crowding out trees. At the same time, Dutch elm disease, bark beetles and other ailments are attacking trees, and cities don’t have any money to plant new trees or even maintain existing trees. It’s ever more important for urban gardeners to plant the right trees in the city.
Why Plant Urban Trees
According to the Environmental Protection Agency, a large urban tree provides 10 to 20 times as much ecological benefit as a large forest tree. Trees trap or absorb particle pollution, carbon dioxide and other greenhouse gases. They also generate oxygen and help cool the air, reducing the urban heat island effect in cities. They also reduce runoff.
On a smaller scale, the right trees in the right spot can reduce heating and cooling costs by blocking summer heat or winter wind.
The benefits are tangible and quantifiable. According to research at the Forest Service and the University of California, one large tree in an urban front yard in central California offers $111 in benefits, including $30 in savings on air conditioning bills, $45 in emission reduction credits for absorbing air pollution, and $6 in savings on water quality management and flood control costs.
What to Look for in an Urban Tree
In choosing an urban tree, look for the following qualities:
• Appropriately fast growth to a size at full maturity that provides enough shade without becoming overwhelming or dangerous. Keep trees under 30 feet tall around utility lines or in restricted spaces. Also avoid trees with strong, wide-reaching roots that could damage foundations or sidewalks.
• The ability to grow in your hardiness zone, as shown on this U.S. Department of Agriculture map
• Partial shade tolerance, if necessary
• A tolerance for salt and potentially weak urban soils, which tend to be dry, compact and sandy
• The ability to tolerate pollution, pests, diseases and other urban ravages
• Strong, sturdy limbs
• Lack of thorns, particularly around children.
A Few Good Trees
Though it seems like a tall order, here are a few trees that fit the bill. The U.S. Forest Service, the Ortho Books Complete Guide to Trees and Shrubs, and the Cornell University horticulture department all endorse these trees for urban gardens.
Amur Maple: This native of China and Japan is more tolerant of a range of soils and shade conditions than some maples, and grows up to 20 feet tall and wide. It is showy and bright red in the fall, and very cold-tolerant, growing well in zones 3 to 8.
Cumulus Serviceberry: This single-trunk tree attracts birds and offers year-round color, with white spring flowers, small red summer berries and orange fall leaves. It is ideal for streetside planting, and also grows in zones 3 to 8. It reaches 25 feet tall and 15 feet wide.
American Hornbeam: Also known as musclewood, the tall hornbeam typically has a long sinewy trunk capped with a ball of blue-green leaves. The shape lends itself to streetside planting, and grows in zones 3 to 9. It grows slowly, and hardily tolerates flooding and shade. It reaches up to 30 feet tall and 25 feet wide.
Goldenrain Tree: This tree only grows from zones 5B to 9. However, this 30-foot tree makes up for not tolerating cold by tolerating heat, drought, pollution and poor soils. It also has bright yellow flowers in the summer when few other plants are flowering.
Crabapples: The hundreds of varieties of crabapple tree have beautiful white, pink or red flowers, and namesake fruits that last well into the fall. Sizes vary but many don’t exceed 15 feet tall or wide. Be sure to choose a disease-resistant cultivar. The Forest Service recommends the “David” for its creamy white flowers, and the Prairiefire for its pinkish-red flowers.
Japanese Tree Lilac: This pest-resistant tree grows to 25 feet tall and 15 feet wide flowers best in full sun, but tolerates partial shade. It has large clusters of summer flowers, but they may only appear in full bloom every other year. It grows in zones 3 to 7, but may face some problems in warmer southern climates.
Planting urban trees can make you a responsible environmental steward while also making your home more comfortable and reducing energy bills. However, choosing the right trees for the urban environment is crucial. These six trees should spruce up any city garden, and plenty more suggestions are available in this slideshow and this comprehensive directory.