The Waltham Forestry Division is currently in the process of completing an Inventory of all the public trees in Waltham. See more details here:

Waltham Tree Inventory Currently Taking Place:
Noticing any metal tag numbers on trees around the city? The Waltham Forestry Division is currently in the process of completing an Inventory of all the public trees in Waltham. As of February 1st, 2017, Ward 4-1,4-2, 6-1, 8-1 and 9-2 are complete (the Inventory will be ongoing until complete). The Forestry Division has been able to capture significant information, including tree species, diameter, health, and a host of other statistics that will be used for maintenance planning and reforestation. The data also will quantify CO2 sequestration, energy savings, annual costs, storm water interception, and other data.
Residents can view all the collected information using our “Maps Online” feature on the City Website: http://bit.ly/walthammapsonline
Once you type in an address you will be taken to the overhead map. Select the “Tree Inventory” tab at the top of the page. If your (public) tree has been inventoried it will appear as a green irregular shape. The 2004 inventory trees are shown in red. Click the round blue “i” icon at the top right and then click on the tree to see the collected data.
The program is in its infancy and volunteer data collectors are appreciated. Please contact Tree Warden, Kevin Thompson at (781) 314-3850 or kthompson@city.waltham.ma.us. The Forestry Division uses “I-Tree Streets” for data collection, which can be used on many smartphones and tablets: http://www.itreetools.org/streets/.