"The best friend on Earth of man is the tree. When we use the tree respectfully and economically, we have one of the greatest resources of the Earth."
Frank Lloyd Wright
Street trees can add interest, beauty, and value to a city's forestry landscape. There's nothing quite like driving down any city's oldest thoroughfare lined with large, historic street trees. If planted knowledgably and with care, street trees will bring urban beauty for decades and maybe centuries to come. To ensure that you have the best fit for your street tree, it is important to evaluate the location you are considering and then get the best tree to fit the space.
In the beginning stages, it is important to understand what features of the area need to be addressed. Is it a busy intersection where the views will be unsafely blocked? Is there a storefront that you don't want to block? Is there a new curving sidewalk of which replacement cannot be afforded? Survey the area with these and other questions in mind. Once you understand the area, then you can begin to choose the correct tree.
What makes a good street tree?
Slow to moderate growth Trees that grow tremendously fast, such as cottonwoods, poplars, and blue spruces, present many different problems. Fast growing trees tend to be short lived with weak wood. You want to plant trees that have moderate to slow growth such as dogwoods, ginkos, and maples.
Little to no suckering Some trees like aspens, chokecherries, and the Amur maple constantly send out annoying suckers and shoots as they grow. These are natural and healthy functions of reproduction, but in a confined space such as a hellstrip or street planting, many times suckers are unwelcome. Choosing a tree that rarely send out new basal growth will ensure a tidy, standard growth pattern for your street tree.
Tough/hard wood Because the trees will be living in conditions most trees will never experience, such as car exhaust, salt and sand, as well as the possibility of an occasional mishap (see below), the tree needs to be tough and strong. Spruce, pine, and poplar are trees with rather weak wood that could easily suffer cracks, falling limbs or damage structures and cars in close proximity to a busy street.
Teenagers going 80 mph took out two young trees and a shopping center sign near my house
Shape This might seem like an obvious one, but don't plant a tree that has a natural growth pattern than will get in the way of sidewalks and cars. Trees with low branches or pyramidal shapes, such as the Persian ironwood or blue spruce would make annoying and unsafe street trees.
Long lived Street trees grow more beautiful and charismatic with age, so why would you want a tree that would be short lived? Love lived trees such as live oaks, maples and elms make great street trees because of their longevity and the unique characteristics they take on with age. Along with longevity comes disease resistance. Some trees will be more susceptible to disease in certain areas of the country than others. Be sure to find a tree that is generally healthy and successful in your area before you decide to plant it.
Deep roots Because street trees by definition are in close proximity to sidewalks, driveways and roads, it is wise to plant trees with deep roots so as to not disrupt the surrounding pavement. According to Iowa State University's Extension Agency, you should avoid planting trees in areas with less than three feet between paved areas. In areas with 3 to 4 feet between paved areas, plant trees that grow to a mature height of less than 30 feet. In areas with 5 to 6 feet between paved areas, select trees that mature to about 50 feet tall. Reserve trees that mature higher than 50 feet for areas with at least eight feet between paved areas. Properly picking the tree for the available space will allow for proper root growth.
Trees with shallow roots to avoid as street plantings: Norway maple (Acer platanoides), red maple (Acer rubrum), sugar maple (Acer saccharum), ash (Fraxinus spp.), sweetgum (Liquidambar styraciflua), tuliptree (Liriodendron tulipifera), pin oak (Quercus palustris), poplars and cottonwoods (Populus spp.), willows (Salix spp.) and American elm (Ulmus americana) (1).
Street Tree Suggestions
It is wise to search for trees that will be successful in your specific area. Search online for "street tree recommendations" in your state or city. Most of the time county extension agencies or city governments will put out a list of suggested trees. Some trees that can work just about anywhere in the US:
Lacebark Elm (Ulmus parvifolia)Willow Oak (Quercus phellos)Japanese Zelkova (Zelkova serrata)
The dendrology department at Virginia Tech University provided an excellent resource for street tree selection. It is specifically geared to the Virginia climate and conditions, but could prove helpful for anyone trying to choose a proper street tree.
Arbor Day Foundation also has an excellent tool to help you choose the proper tree for the proper location.
Many larger municipalities will offer assistance for planting street trees. For example, Colorado Springs offers free street trees to homeowners who live on busy streets around the city. Homeowners are able to choose from a list of preapproved trees and can receive assistance in planting the tree. Programs such as this encourage urban forestry, ensure that the proper trees are selected, and increase the property value for the city and the homeowner. Colorado Springs has enjoyed success from urban forestry planning and now celebrates 99,000 inventoried street trees in the city limits (2). Look for programs such as this in your neck of the woods to help with information and the cost of your new street tree.
Take proactive care to survey the intended location and research trees before you plant a street tree. With any luck (or planning) you and many generations to come will be enjoying your new tree.