Tree Root Architecture
Information on research of tree root architecture, root excavation, 3D-digitising of root systems, tree root growth, tree stability, and windthrow.

International Dendrological Research Institute
Nonprofit organization dedicated to documenting the woody flora worldwide.

TreeGuide
Includes information about almost all North American trees, with brief descriptions, range maps, and a few images. Brief family summaries for trees from elsewhere. List of state and provincial trees.

Tree Matters
Site for The Dendrologist, a quarterly magazine. Also contains tree tips and a record of the dates of upcoming dendrology events in the UK.

Forest Biology and Dendrology at Virginia Tech
Information about courses, trees, and forest biology. Includes fact sheets on over 450 species of trees.

The American Woods
Wood sections of 350 North American trees from the 14-volume book The American Woods, published between 1888 and 1910 by Romeyn Beck Hough.