Story and Photographs by Joan Herrmann

Whereiwander… about ten years ago, while working at a local outdoor educational/nature program, is when I truly became curious about galls. At that time I had no knowledge about what they were, what caused this phenomenon, and that they occurred in many different sizes and shapes. One of the first galls to catch my attention is one that can readily be found in our meadow. They are quite obvious in early summer when the goldenrod plants, which are numerous and quite tall, dominate the wildflower meadow. The goldenrod gall is produced after, a rather small fly known as the Goldenrod Gall Fly (Eurosta solidaginis) lays her egg, both singly and exclusively on the goldenrod plant stem. The fly inserts her ovipositor into the stem and deposits the egg. Once the egg hatches the larva will secret its saliva within the stem which is an irritant to the plant; the plant reacts much the same way we do when a black fly bites, draws blood, and secrets its saliva onto our skin.

When we are bitten our body reacts to the irritant fly saliva and the site begins to swell. The goldenrod plant reacts in a similar manner producing plant tissue around the intruder (the goldenrod gall fly larva) and produces a green gall on the plant’s stem. The larva is now protected within the plant tissue which is in the shape of a green ball. The gall will provide food and shelter for the larva throughout the summer, fall, and winter. The plant will change color as it ages in the fall and the gall will appear as a brown ball shape on the plant’s stem. Once the temperature drops the enclosed larva will produce a type of “antifreeze” known as glycerol which will keep it from freezing inside the gall. The larva will be dormant throughout most of the winter in an insect sleep known as diapause. When the temperatures rise and the daylight becomes longer in the springtime, the now active larva will chew an exit tunnel through the gall. When it has achieved an exit opening it will lightly seal the exit hole. Then the larva will begin the third stage of metamorphosis and begin its pupal stage. Upon completion of the pupal stage, the adult fly will emerge and will then use the previously chewed tunnel to escape from the gall. The adult fly will pump fluids into its head and pushes its “bubblehead” through the lightly sealed exit hole. It is also interesting to note that the seed production of the goldenrod plant decreases by forty percent as a result of the gall; which is another example of disease and insects keeping our native plants in balance.

Galls may be found on plant stems or on its leaves. The Willow Cone Gall was the next gall that was intriguing because its shape resembles a pine cone. We know that pine cones grow on conifer trees, but while exploring the bog with some of my students, we noticed what appeared to be a “pine cone” on a deciduous tree. The tree was actually a willow and we knew that willow trees don’t produce cones. It was a mystery that needed solving. It took a while but, I learned and was able to share with my students that it was gall and not a cone. The gall was created in a similar manner as the goldenrod gall fly larva produced the goldenrod gall. The insect that produced the cone-shaped gall was actually a tiny midge (Rabdophaga strobiloides). It initiates a gall found at the tip of a willow stem. The gall is cone-shaped and comprised of numerous stunted, overlapping willow leaves. Like the goldenrod gall which is green in summer, so too is the cone gall green in summer and it turns a whitish-gray in winter.

In addition to numerous species of insects utilizing this method of protecting their eggs throughout the seasons, and their metamorphosis stages, galls may also be produced by fungi, nematodes, and bacteria. The Oak Apple Gall is produced by a wasp (Amphibolips confluent). However, it is only one of more than eight hundred different galls that are produced by Oak trees. The oak apple gall is about the size of a golf ball and it is green in summer which gives its apple appearance but will turn a papery brown color in fall and winter. This past year I also found a Wooly Oak Leaf gall that was induced by a wasp (Andricus quercuslanigera). The gall looks like a tiny wooly ball and can be found attached to an oak leaf.

Another rather interesting gall is one produced on Red Maple leaves. Maple Eye Spot Gall is very interesting and colorful. The leaf appears to have numerous bull’s eyes on it and the gall is produced by a midge (Cecidomyia ocellaris). I found several of the galled leaves on a hike in the Rome Sand Plains. In addition to plants and trees, vines like our wild grape vines are also hosts to insect galls. Grape Phylloxera gall is a notorious pest of vineyards native to North America. It was accidentally exported to Europe in the mid-1800s, nearly destroying the French wine industry before resistant rootstocks were shipped from the United States to salvage the crops.

Of the two thousand gall-producing insects in the United States, fifteen hundred of them are wasps or gnats. As I mentioned earlier Oak trees have over eight hundred species, the Daisy family has nearly two hundred species of insects, the Rose family more than one hundred species of insects, and the Willow family also has more than one hundred species of insects. For the most part galls generally create a win-win situation giving food, shelter, and protection for the larvae and as a rule, do not harm the plant. We have benefitted too as there are a number of ways that we have found to utilize galls; making medicine, insecticides, and permanent ink because of the large amount of tannic acid contained in the galls.

I hope that you have an opportunity to find a few of these interesting and fascinating galls.


As a Professional Nature Photographer, Naturalist, and Outdoor Educator, Joan Herrmann has been teaching and doing programs for Schools, Garden Clubs, Libraries, and Nature Centers, about 38 years. After moving from the Rochester area in 1995 she began her Photography business, Essence of Nature, and also became a co-owner of The Artworks in Old Forge, New York. As a docent at Munson, Williams, Proctor Arts Institute, in Utica, New York she has been educating children and adults, for nineteen years.

In 2007 she began working with the Black River Outdoor Educational Program (BROEP) and in 2013 and 2014 did a week-long summer program at BROEP in conjunction with Mohawk Valley Community College (MVCC). Using her love of both nature and photography she created a Flora/Fauna outdoor educational program teaching students (ages 6 to 14) the joys of nature and creative photography skills.

Joan’s love of nature has been a lifelong study of Birds, Wildflowers, Mosses, Ferns, Trees, Amphibians, Reptiles, Grasses, Insects, Spiders, Tracks, Scat, and Galls. She has assisted in the cataloging of all trails used by the hiking Coaches and photographed and identified seasonal Flora.

Since October 2016 she has been writing a bimonthly nature column with Adirondack Express Newspaper. In October of 2019, she began a bi-monthly column with My Little Falls Newspaper. You may reach her at jmhphoto8442@gmail.com