Formal:
* Arborist: This is a professional who specializes in the care and management of trees, including planting.
* Forester: Someone who manages forests, often including planting trees for reforestation.
Informal:
* Tree planter: This is a straightforward description of someone who plants trees.
* Green thumb: This is a general term for someone who is good at gardening, which could include planting trees.
* Environmentalist: Someone who cares about the environment and might plant trees as part of their efforts.
You could also use phrases like:
* Someone who plants trees
* A tree-planting enthusiast
The best term to use will depend on the specific situation and the level of formality you need.
