It is tough. I use the buildings as a reference. My method is the following:
1. Walk around and record audio
2. Ensure buildings are correct
3. Call out trees based on the building property wall. Eg: tree at 20% through Brigade Hallmark; etc.
4. Listen to the audio and add the trees
5. Later I will try and add details to the trees like species and width, etc.

This only works for the avenue trees though. Many in this neighborhood. Not sure how others have mapped trees in parks.