Tips for Gall Hunting
Tips on Gall Hunting; Where and When to Hunt for Galls
Think about sites that have mature trees with low-hanging branches. Sites that have been quite good for me include city parks, cemeteries, and forests with lots of edges where the forest meets open ground, such as fields or prairies. Galls are often on large tree species, so closed forest environments can be more difficult, especially if you are looking for galls on shade-intolerant species such as oaks. Forests with edges next to prairies are particularly fantastic as you can find galls on the trees and the herbs.
Areas of high human impact have some influence on the frequency of gall species, at least the more uncommon species. However, do not disregard manicured areas such as arboretums, city parks, golf courses or even tree lawns as they will often have galling species. For example, I found 20 or so gall species on the highly managed "Oval" on Ohio State University's main campus. Diversity does tend to be lower in these spots but do not discount them as a place to look.
If you just want to find a gall (any gall), seek out sites with plant species that have a huge diversity of galls. Examples of species with large gall diversity include; Quercus (particularly alba, coccinea, stellata), Carya (in late summer many of these will have a half dozen gall species), Celtis (many here in Ohio have 5-6 species on a single tree, although I am not sure how far east some of these go), and Solidago/Euthamia. iNat distribution maps and geotags can be useful for finding these sites. Another recommendation if you are looking for a particular host is to do a search for the common name of the host on your state's DNR website, they will often list some of the common species that are located at a given nature preserve or state park.
If you are looking for a specific gall, try to find a site where the host is regionally native and common. Trees that are native and more common in a region will tend to have higher diversity. For example, Quercus macrocarpa and Quercus muehlenbergii are native but uncommon in NE Ohio. I have found far fewer gall species on them in this area compared to western Ohio where both species are much more common. Hackberry, Celtis occidentalis, is another example of this, it becomes much more common as you move south and west in Ohio and the diversity of galls seems to increase in that direction.
If you notice that a particular tree has a large number of galls, keep visiting that tree repeatedly through the course of the year and even over multiple years, and you will likely run into new species. It seems like some trees have something like a susceptibility factor or alternatively, some kind of environmental niche like wind direction that seems to make them more galled than others. These trees have been a rich source of new species for me.
Mid to late summer (July-September) is the best season for hunting galls in Ohio. The highest number of species will be around during that time. However, if you want to find rarer or underreported stuff, look for galls during what might seem like the offseason. For example, early spring (March-May) has many interesting oak bud galls. October has another subset of oak galls that appear just as the leaves are turning that don't often get reported. November and December after the leaves fall can be a good time to look for galls in the leaf litter of more closed forests.
