City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!
Issue link: http://read.dmtmag.com/i/540151
root (BR), and this past year we installed six crabapples that were produced in grow-bags. I've found with each of these systems that there are strengths and weak- nesses. B&B is more readily available but the digging process removes 80-90% of the roots, which puts great stress on the tree. On the other hand, CG trees have all of their roots, but circling roots can be a problem, especially over time. With the BR system you can have a complete root system, but there's often limited avail- ability depending on where you live. Also BR trees have to be handled properly and quickly to avoid the roots drying out; BR requires more planning. Of course, I try to plant a few trees myself every year and I enjoy how light and maneuverable the BR trees are. RH: Who is planting your trees? DL: Like all urban foresters, three different groups are planting our trees: sub-contractors, our in-house crews, and volunteers. Sub-contractors have the means to work the fastest, but with that comes the need for me to be vigilant in terms of quality control—e.g., making sure trees aren't planted too deep. With an in-house crew, I have more oversight and control but the number of trees planted may not be as numerous. Volunteers take ownership and even provide after-care, but their knowledge base may not be equivalent to that of a pro- fessional, so following up to answer questions and to ensure quality is important. RH: What do you use to guide the planting pro- cess in Cambridge? DL: Any community should have good tree planting specifications that are updated regularly. I'm always try- ing to update my specs based on emerging information or on something I've noted on a recent project, so we are already on our third edition and I'm happy to share what we have with other communities. I've realized that I do work with a lot of crews that speak Spanish or Portuguese, so we are working to get a version in those languages to share with these contractors and their crews. RH: What tips can you share on how to properly install a tree and avoid some of the common mistakes? DL: Since the vast majority of what we plant is B&B trees, I will speak to that. The first thing that I recom- mend is to make sure that the twine is removed from around the base of the tree and above the roots. This is important first, because synthetic materials don't break down over time and can create root interference and second, because doing this allows us to find the root flare. There are a lot of tools to determine how much excess soil may be present; one is called a "chaining pin." By poking around the top of the ball at about 3-4 inches (8-10 cm) from the base of the tree, we can determine how much soil is covering two or three of the larger, structural roots. Then we simply use a garden claw or small trowel/shovel to find and expose root flare. I've removed up to 24 inches (61 cm) of soil on top of roots! But it is more typically 4-10 inches (10-25 cm). Another benefit of doing this is to reduce the depth of the root ball so that we don't need to dig as big of a hole; we've reduced ball volume by one-quarter to one-third by going through this process of exposing the root flare. This is also an opportunity to uncover and address roots that are girdling or growing irregularly. We dig the hole as wide as reasonably possible but at least twice as wide as the root ball. Then, we place the root ball on undisturbed or compacted soil, setting the tree 1-2 inches (2.5-5 cm) above grade. We do our best to remove the entire wire basket, but removing no less than ½ to 2 / 3 of the burlap and wire basket is the minimal standard that I think we should follow. Then we fill the hole halfway up with soil, and stop to add water—what I call "mudding in" the tree— to help remove air pockets and help secure the root ball in the ground. Then, we fill the rest of the hole with soil and soak again with water. We finish with a nice layer of mulch, taking care not to bury the root flare. Staking a tree is not typically necessary, though in the urban environment it usually serves as a reminder that this is a young tree and that people should exercise a little caution around an establishing plant. Of course we need to remember to remove stakes or tree grates/ guards before they start to wound or girdle the tree. RH: Can you talk about your Water-by-Bike program? DL:Here in Cambridge, all new trees are installed with an irrigation bag. Through our Water-by-Bike program, which we modeled after the one created by Casey Trees in Washington, DC, a summer intern (a "tree ambassa- dor") bikes around the city with a cargo trailer in tow and refills the irrigation bags. The tree ambassador also weeds the tree pits and takes care of litter around the tree. They speak with pedestrians, residents, and businesses, explaining basic tree care and encouraging street tree stewardship. We started this campaign four years ago where we encourage residents and private business owners to feel empowered—and even respon- sible—to water and help care for the newly planted trees in the community. 36 City Trees