Street Trees Save Lives
The life of a street tree isn’t an easy one. Urban trees face stress resulting from the heat island effect, concentrated air & water pollution, compacted soils, and vandalism resulting from vehicle and pedestrian traffic – to name just a few.
Yet street trees are a crucial part of city life. Green “corridors” connect parks and provide essential habitat for wildlife. Street trees act as natural air conditioners, and can cool off residents who are resting on Baltimore’s famous marble stoops. City trees add beauty and increase property values. And most importantly, street trees provide natural stormwater management. This is vital in a landscape of impervious surfaces (hard surfaces such as pavements roads, sidewalks, and rooftops that do not allow water to soak into the ground). Slowing rainwater runoff reduces flooding during heavy storms.
Photos: Blue Water Baltimore staff remove hundreds of square feet of concrete each year to create new street tree beds. We are part of a city-wide initiative to reach 40% tree canopy coverage. Right now Baltimore City is at around ~28%.
Who is Responsible for Street Tree Care?
Street trees are in the public right of way. This means the trees are City property and under the care and jurisdiction of Baltimore City Recreation & Park’s Forestry Division, although residents are tasked with keeping the area around the trees clean*. However, some residents take street tree maintenance into their own hands. This blog reviews some of the basic “Do’s & Don’ts” when it comes to helping our little leafy friends.
What Do Street Trees Need to Thrive?
It’s awesome when Baltimore’s communities show our trees some love! You can clearly see local resident’s creativity and pride through the unique decorations in the images below. But what do street trees actually need to thrive? And what types of care might cause inadvertent harm?
Here’s the short version: The best love you can give your local tree is regular watering in the summer & a nice helping of mulch each season. That’s all folks!
Street trees require weekly watering May-October for the first two years after planting. Transplanted root systems are small and need time to establish. After that period, occasional watering during a drought will help them survive.
Mulch assists by insulating roots and acting like a sponge to hold moisture. As wood chips break down, they add nutrients to the soil. (Note: always keep mulch away from the trunk or it can damage and kill the tree. Think ‘donut’ not ‘volcano’.)
Photos: These tree beds might look a little boring, but they do the job!
(Note: The plastic rings around the tree trunks are called ‘Greenwell Water Savers.’ They hold up to 15 gallons of water that slowly infiltrates into the ground allowing for maximum absorption by the roots.)
DIY Barriers, Borders, Walls, & Fences
Many residents install homemade structures around their local tree beds. These are built for a variety of reasons: for aesthetics, to protect flowers or shrubs, to block litter from collecting, and to prevent dogs from entering. We salute everyone who works hard to beautify their community by taking care of their local tree bed!
From the tree’s perspective, however, the main reason to install a fence should be to prevent soil compaction. Each time someone walks across a tree bed, their weight condenses the soil. Urban areas often have intensely compacted soils due to decades of development. Compaction destroys fragile roots ability to absorb water. It can eventually block water from entering the soil at all, turning the bed into an impervious surface. Soil compaction is very difficult to reverse.
While many DIY fences around tree beds do block pedestrians from further compacting the soil, these barriers also stop rainwater from entering. It is essential that any sort of fence that you build around the bed should be raised at least 2 inches off the ground to allow rushing water to enter the soil.
Photo: While not the showiest fence around town, this barrier functions well for the tree because it both blocks pedestrian traffic & allows stormwater to enter the bed and infiltrate into the ground.
The following photographs show structures that block water from entering the tree bed, and while they are creative and industrious, these types of barriers should be avoided:
Photo: This simple wooden border is still a few inches too high.
Photo: Nice idea to use cinder blocks as planters for added beauty! However, this wall does not allow water to enter at the sidewalk level. (Always choose native plants if possible!)
Show Me Your Root Flare
Another major problem with DIY barriers is that they sometimes raise the soil level inside the tree bed so that the the base of the tree trunk (called the root flare) becomes buried by inches of soil or mulch. Buried bark will decay over time and invite pests and disease. Raised soil levels also significantly increase the likelihood of roots growing up and girdling the trunk. These issues all lead to early death. There,fore, the soil in the tree bed should always remain level with the surrounding sidewalk.
Our mulching blogpost has all the details, but this is just a note to avoid synthetic and dyed mulch. These materials leech chemicals and pollute our waterways. Also, mulch should be spread out across the bed and never touch the tree trunk.
Photo: Rubber mulch does not decompose or add nutrients to the soil. It contains chemical residues that can actually harm plants. It also erodes during large storms and enters the Chesapeake Bay as pollution.
Photo: Red mulch leeches toxic dyes into our waterways.
New trees should held up with two stakes for the first year after planting. Recently transplanted trees have not yet grown structural roots in the surrounding soil. Stakes act like training wheels on a bike for the tree – they hold it up straight and steady it from falling over. Generally, stakes should be removed after the first year to allow the tree to become established and stand on its own.
Photo: A correctly staked & tied hawthorn tree in the West Baltimore neighborhood of Mondawmin.
Photo: Even though it was built with good intentions, this DIY wooden post is too close to the trunk of this flowering cherry tree. If you look closely, you can see that it rubbed against the bark enough to create a wound, which will open the tree to possible infection. If not removed soon, the tree will begin to grow around the post, leading to further damage.
Like stakes, tree ties should be removed after the first year. Otherwise, they pose a major threat to the health of your tree. Leaving strings or ties on branches too long can cause girdling by cutting off circulation to the leaves.
Photo: Underneath the bark, these wire ties are blocking the tree’s main arteries that transport food and water between the leaves and roots.
Photo: If you notice any stakes or bamboo poles tied tightly around the tree trunk, please remove them!
Additional Plants in the Tree Bed
For some residents, tree beds may offer the only opportunity for gardening. While it might be tempting to fill the tree bed with additional plants to add beauty and color to your block, in most cases it isn’t great for the tree. It comes down to a competition for much needed resources (food & water).
If you are determined to plant flowers, at least wait until the tree has been in the ground for a full year so it can become properly established in its new environment. Aim for native perennials. Perennial plants (unlike annuals) return each year in the spring, and so you won’t keep disturbing the soil. Repeated soil disturbance harms shallow tree roots. Also, go native! Native plants are adapted to our local climate and support local wildlife. To learn more about native plants and their many benefits, check out Blue Water Baltimore’s Herring Run Nursery.
Photo: These Greektown residents obviously had a lot of fun filling their street tree beds with squash plants! However, to fully thrive, squash need full sun and a much higher water requirement than just flowers. In essence if you want the tree to succeed, then the squash really can’t and vice versa.
Removing Grass, Weeds & Climbing Vines
Photo: Mowing is not only more aesthetically pleasing for residents and passerby, but also allows young trees to absorb more water.
Photo: NOTE: When removing grass and weeds, beware of damaging the tree trunk with your mower or weedwacker. Trees cannot heal from wounds. They merely seal, block off, or compartmentalize the damaged area. Protect your tree by adding a plastic mower guard as shown above.
Photo: Always remove climbing vines from around your tree. This invasive morning glory will eventually block sunlight (& photosynthesis) from the leaves of this buckeye tree in Greektown.
Tree pruning involves the removal of broken, diseased, dead or crowding limbs. It can also be done for aesthetic or practical reasons, such as to remove lower branches that are blocking pedestrian access. By pruning trees when they are young, we ensure that they grow up to be a strong, healthy canopy in the future.
However, pruning must be done correctly to avoid damage. It is also beneficial to wait to prune until the tree has been in the ground for at least 3 years so that it is established and can properly heal. After that, trees only need to be pruned every five to seven years. Never prune more than 25% of your tree at a a time. (The leaves provide food for your tree so if you remove too many, it will starve.)
If your street tree needs pruning, call 311. You can also download the 311 app or submit a request online (This way you can upload a photo which is helpful).
Never prune your own street tree without some prior knowledge of tree biology. If you want to learn proper pruning techniques to maintain your own trees, become a Baltimore TreeKeeper!
Organized by TreeBaltimore, The Baltimore TreeKeepers is a city-wide tree stewardship program open to anyone interested in Baltimore’s trees. TreeKeepers promote healthy trees by educating residents and increasing their role in the care of the City’s trees. Through this training, citizens can become tree advocates and share the responsibility to plant and care for trees in their neighborhood and throughout the City. Plus it’s a great way to get to know other tree people 🙂
Photo: Staff and volunteers enjoy a tree pruning party in the Oliver neighborhood.
We encourage Baltimore residents to take ownership of their local tree beds! Let’s add more beauty to our city! Most decorations are generally harmless to the tree unless they involve digging into the soil (root disturbance) or if they are wrapped tightly around the trunk or branches (restricts growth.)
Photo: Did you know there are more plastic pink flamingos in the world than real ones? These types of fun decorations don’t harm your tree, but their production and eventual disposal aren’t great for the environment.
Photo: We all want to show our support of the Ravens by painting the town purple, but skip the tree?
Generally, painting the trunk of your tree is not a good idea. Think of tree bark like human skin. Water-based, temporary paint is non-damaging if you wash it off after a short period of time. However, permanent oil-based paint will cause long-term health issues. Trees have pores in their bark, called lenticels, that facilitate gas exchange. Covering up them up reduces respiration. Basically, your tree won’t be able to breathe!
Photo: This bench is a nice touch, but was built a little too close to the tree. It will need to be moved in the next couple of years or it will restrict trunk growth.
Photo: String lights look beautiful but can cause serious damage to trees. It is okay to install these loosely around the trunk for short periods of time, but they must be removed or adjusted as the tree grows wider in diameter.
Photos: Spooky spider webs & festive tinsel won’t harm your tree as long as you remove them after the holidays. (Note: The wooden border in the photo on the right is blocking stormwater. It also raised the soil level in the bed so that the tree trunk is buried. The lifespan of this Eastern redbud in Hampden will certainly be limited as a result.)
General Street Tree FAQ’S
Visit Baltimore City Forestry’s web page.
How Can I Get A Tree?!
Don’t have a street tree yet? A request can be made to the City by completing a Tree Planting Request Form. If you have an existing dead tree or stump, you will also need to contact the City for removal prior to planting.
You can find a list of approved street tree species here: Approved list of trees from Baltimore City Forestry Division
Have a Problem With Your Existing Street Tree? Call “311”
Residents should never try to deal with a public tree problem on their own—even if it’s in front of their home! They should call 311 and report the problem. Trees on private property, however, are the responsibility of the homeowner.
Check Out the Baltimore City Tree Inventory!
Curious to learn more about our current tree canopy? Baltimore City Department of Rec & Parks recently inventoried all of our street trees! Take a look at the regularly updated map here.
Finally – Show us your tree!
How have you cared for your local street trees recently? Take photos and tag us @bluewaterbmore and @treebaltimore or email images to [email protected]
*Correction: This post has been updated to more clearly delineate the maintenance responsibility of the city and homeowners.