Like many urban dwellers, trees in the city make do with less space. The urban tree’s “apartment” is a tree box, an open and unpaved area in the sidewalk specifically set aside as a home for a tree.
Street trees are a valuable part of our urban landscape. These trees provide shelter for wildlife, shade from the hot summer sun, and clean our air. To ensure that your tree box residents stay happy and healthy, keep these guidelines in mind:
Do NOT disturb or harm tree roots.
If you decide to add plants to a tree box already housing a tree, do not use a rototiller or mechanical device to break up the soil. Most of a tree's roots are found within the upper 6 to 12 inches of soil and they can be easily severed by these devices. Severing one major root can cause the loss of up to 20 percent of the root system and affect its ability to anchor the tree.
Do NOT add plants that will compete with the tree.
Tree boxes are designed specifically to accommodate trees. Flowers and other small plants can compete with the tree for water and other nutrients potentially stunting its growth.
If you must add plants, follow the District Department of Transportation (DDOT) Landscaping Design Criteria (47.5.2 Plants). Use plants that have a shallow root system, do not grow taller than 18 inches and will not extend outside of the box borders.
Also remember that tree boxes are considered public space. The District reserves the right to enter the tree box for construction and maintenance activities. DDOT will notify the abutting property owner if any beautification materials need to be removed to complete their work so that the owner may do so prior to the start of construction.
Do NOT change the grade or height of the tree box.
You may only add mulch to the tree box. Apply using the 3-3-3 Rule.
Do NOT build a solid border around a tree box.
Tree boxes must allow water to flow. Tree boxes made of brick or wood divert water around the box robbing the tree of water and contributing to stormwater runoff. The best type of tree box border is one that allows water to flow into the soil while also protecting the tree from the denizens of the sidewalk.
It should be three-sided, with the street side left open to prevent damage to vehicles. It should also be tall enough to prevent being a tripping hazard. 4 to 12 inches is a good rule for border height.
Read our Tree Space Design Report for innovative ways to create ideal environments for urban trees.
Do water your tree regularly.
Newly planted trees, those that have been in the ground less than three years, need regular watering to become established and thrive. Practice 25 to Stay Alive by watering trees on and surrounding your property 25 gallons of water per week. Casey Trees provides complimentary Ooze Tubes (drip irrigation bags) to help DC residents water their trees.
If you make the 25 to Stay Alive pledge, we will also send you a complimentary rain gauge to monitor rainfall totals at home. If you receive less than 1.5 inches of rain, it is time for you to water your trees.
Do remember that tree boxes are first and foremost for our trees.