This is an elm near the corner of Avenue A and East 7th Street. I noticed these growths on the leaves. With help from reddit.com/r/whatsthisbug/ I found out that they are finger galls. Bottom line: Icky but not dangerous to the elm.
Galls are formed by insect/mite feeding or egg-laying activity. Either mechanical damage or salivary secretions (introduced by insects and/or mites) initiate increased production of normal plant growth hormones. These plant hormones cause localized plant growth that can result in increases in cell size (hypertrophy) and/or cell number (hyperplasia). The outcome is an abnormal plant structure called a gall… Most galls do not adversely affect plant health. Therefore, management is generally not suggested to protect plant vitality. extension.umn.edu

I took this photo as a part of my ongoing Tompkins Square Park Tree Identification Project. As an update on that, It’s already been done. A very nice wall map is available from East Village Parks Conservancy for $20. The map was a 1998 project of what looks to be a collective of volunteer artists and cartographers. The map uses common names and is not species specific, and of course some of the trees on the map are no longer there. The project I am still thinking of is web-based, species specific, and probably way too much work for me to do on my own. I think I will start with keeping an eye on the oldest and largest, and most interesting trees over the course of a year and see what happens.

Filed under: East Village, Manhattan, Parks, Photos , Tompkins Square Park, trees, TSPTIP by gamma