In Northwest Indiana, a new urban forestry effort called CommuniTree has emerged with a goal of helping solve some of the region’s post-industrial social and ecological issues. Though no panacea, tree planting can have significant benefits, including air pollution abatement, temperature moderation, stormwater management, and beautification. CommuniTree is a Collective Impact-style collaborative of over a dozen partner groups (public, nonprofit, private, and partnership organizations) that plants trees on public and industrial properties in post-industrial Northwest Indiana communities where urban forestry governance and resources are relatively lacking. This paper presents the results of the first phase of a transdisciplinary research program that draws insights from urban forest governance scholarship and transdisciplinary sustainability science as well as from urban forest professionals involved in CommuniTree who helped design the research. We used a transdisciplinary case study approach with qualitative interviews with key informants from CommuniTree partner organizations to investigate partner organizations’ motivations for participating, desired outcomes, and long-term visions for CommuniTree. We find that the CommuniTree partnership itself is an intrinsic incentive to partners’ participation: once an influential champion brought the group together, they were motivated to stay involved by the work and structure of CommuniTree. The scant existing urban forest governance in the region also motivated partners to contribute to CommuniTree collective action. For desired outcomes, we find that partners are interested in the potential improvements to ecological quality that may result for the region such as improved stormwater management and air quality, but that more than ecological outcomes, partners are interested in the social outcomes that might come of the CommuniTree, including engaging communities in ecological stewardship activities and the beautification and general improvements to public spaces that result from tree planting. And for its future, partners conveyed a plurality of visions for CommuniTree’s growth including expanding the program to new communities, planting trees on new types of locations, and involving more partners, the general public, and new volunteer groups. However, current CommuniTree structure has vulnerabilities to its sustainability and longevity, including a reliance on predominantly grant funding, shifting organizational dynamics within/among partners, and a lack of systematic integration of the voices of local community members. In conclusion, this research on CommuniTree’s structure and function (i.e., the governance and activities) and on what partners value as desired outcomes and for the future informs an understanding of the vulnerabilities and opportunities for CommuniTree as the program evolves to better meet the needs of current partners, future stakeholders, and, most importantly, community members.