Gall Week 2021 recap

The first ever Gall Week event took place between 10/2-10/10/2021. As the project had only materialized two weeks earlier, it was incredible to see how many people participated, uploading observations and identifying photos. It was fascinating looking at the diversity of galls - colors, shapes, host plants, and gall inducers. People spent time documenting many galls and identifying other people's observations.

A map of the 6,418 observations, from 28 states in the US and 15 countries outside the US, including Botswana and South Africa :

The best part was scrolling through all the beautiful photos of galls from around the world. Here are a few examples:


When looking at how many observations each participant uploaded, it is clear that a large group of people shared the majority of observations, with 92 people sharing 10 or more observations. One of the goals of the project was to include both experienced observers and beginners, people who never looked at galls before. I was hoping to expose new people to the diverse and little-known world of galls. And from reading some of the comments, it worked. Some of the participants knew little to nothing about galls before participating.


We documented galls on many oak species, in North America and Europe. Many other galls were found on Willows, Hickory, Goldenrods, and others.

Other host plants had fewer gall species, but contributed to the overall diversity. On a 3 hour gall hike in the Bay Area in California, we were able to document 46 gall species on 16 host plants. You can view most of them here.



Identifying all these observations, from so many localities and host plants, is not an easy task. 169 people helped identifying the observations so far, of which 11 people identified over 100 observations each. Gallformers.org and its team have been extremely helpful among others. For this reason, we already have 67% of the observations at research grade! This is not an easy task, as in addition to issues other iNaturalist projects are facing, a gall project is facing unique challenges, as there is a high number of undescribed species, yet to get their scientific name. But this is also the most exciting part - how many new species have we documented?

Our work is not done. The documentation portion of the project is over, but there is still a lot of work. We need to identify as many of the species as possible, and make sure unidentifiable observations have enough information allowing future identification.

Would you like to participate in future Gall Week events? When do you think we should hold the next event - should we have one in the spring to document spring galls? Join the discussion on the project page, and join the project if you'd like to be notified before the next Gall Week event. Still need more? Order Gall Week 2021 t-shirt! All proceeds will be donated to iNaturalist.


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