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Episode 252: Oak Apple Galls

Listen to this episode here!

Transcript 11/5/22:

Rest. Finally, after the seemingly endless days of summer and the frantic pace of the harvest season, I can find deep, resounding, guilt-free rest. Welcome to The Nature of Phenology where we share the cycles and seasons of the outdoors. I’m your host, Hazel Stark.

Here we are: November. That moment in the calendar year where I feel poised on a precipice before possibility. Just a little over halfway between the fall equinox and the summer solstice, the harvest is mostly done, the gardens put to bed, the firewood is neatly stacked, the plow guy has been arranged—wait, I forgot about that one! And I still need to pick up the odds and ends in the yard that will soon be hidden or rusted by snow and maybe even build those steps to the front door to replace the makeshift ramp that has been totally serviceable for the past year. This is the moment when our readiness for winter is palpable—we’re either all buttoned up and good to go, or panicking about the tasks that have to get done before snow flies. In an ideal world, we’re good to go, and that precipice of possibility feels like a hopeful one rather than a desperate one: will winter allow me more rest and rejuvenation and clarity or will it be a constant competition with the elements? But let’s not get caught up in what could be. Let’s instead let nature help us focus on the present. One way to do that is to search for oak apple galls.

I don’t know about you, but I get quite glum right after we lose all the colorful leaves of October. I find myself heading to mossy spruce-fir forests to at least get an infusion of green when the rattling brown and gray branches that remain in deciduous forests don’t quite bolster my spirits adequately. Oaks and beech trees both hang onto their leaves a bit longer than our other deciduous trees, like maples, so the top layer of leaf litter where oaks grow is likely to be predominantly oak leaves. In these places, there’s a special little prize you can find on the freshly fallen oak leaves. Oak apple galls are spherical growths attached to the occasional oak leaf and they’re always a treat to come across.

There is amazing variety in the world of galls: color, texture, shape, size, host, and cause. But all galls are a swollen growth on plants, fungi, and even animals. The gall you may be most familiar with, perhaps without even realizing it, is the round gall that grows on goldenrod stems, which is caused by a fly. Oak apple galls are their own special category, though there is variety within that category as well in terms of whether they grow on the leaf or stem and their size and coloration. This time of year in Downeast Maine, I most often see oak apple galls that are no bigger than a dime in diameter, though there are golf ball-sized oak apple galls too.

Look for a beige, papery sphere attached to a fallen oak leaf. Look a little closer and you’ll see a tiny hole in that sphere which tells some of the story of the origins of this gall. An oak apple gall wasp spent its entire two-year life cycle on this oak tree. Females lay eggs in the ground beneath an oak tree. The larvae then feed on the oak’s roots until eventually developing into adults. The female adult wasps climb out of the ground and onto the spring leaves of the oak tree where they insert an egg into the veins of a newly emerged leaf. As the egg develops, it releases chemical signals that make the leaf grow unusually—into that spherical gall that makes the perfect shelter for a developing young wasp. At this point, the gall is usually primarily green, camouflaging it alongside the green leaves of spring and summer. Come summer, the now adult wasp within makes a hole in the gall to make its escape, find a mate, and begin the cycle again. As the leaf naturally withers and browns in the fall, so too does the empty gall.

These galls have a high concentration of tannins in them, which people as long ago as the Middle Ages, and likely earlier, used to make ink. Even Rembrandt and Van Gogh drew with this “common ink.”

So the next time you have the gall to get glum about this gray season, head outside to find a gall. It’s a treasure hunt that’s sure to cheer you up. You can both imagine the life of the little wasp that changed the growth pattern of a mighty tree all on its own, and the humans who made ink and created incredible written and artistic wonders with those galls for centuries.

You can download this episode and find a link to the transcript, photos, information about podcasting and more by visiting Have a nature question or topic that you want us to cover in our show? Simply reach out to us! Thanks for listening and please join us next week for another dive into The Nature of Phenology.


Chudnovsky, S. (2017, July 6). How Wasps Make Beautiful and Complex “Oak Apples” | Brandywine Conservancy and Museum of Art. Retrieved October 26, 2022, from website:

marieflemay. (2013, March 21). Iron Gall Ink. Retrieved October 26, 2022, from Traveling Scriptorium website:


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