International Year of Plant Health 2020 (video)
Tree Benefits Calculator
How To Measure a Tree (Portland Trees website)
https://www.portlandoregon.gov/trees/article/424017
Monica Lewandowski, presentation file
WestFest Trees (pdf)
Healthy plants, healthy planet Activity Book
Free pdf download
http://www.fao.org/documents/card/en/c/ca9327en/
Publication (free access online for this article):
Forest Health Detectives by Tara L. Bal. The American Biology Teacher, 76(8):536-541 (2014). https://doi.org/10.1525/abt.2014.76.8.7
iNaturalist app - identify and learn about plants, animals, insects
More ideas:
Search for nature scavenger hunts to find many more ideas