I've also heard these are a good source of tannins, and were used to make the original iron based inks.
Been having fun finding galls - swellings or growths on leaves & stems caused by insects, mites, & even fungi. There are so many different shapes and they're all so fascinating! You can find many on oak and hackberry trees. Just flip over a leaf! #galls fieldguides.fieldmuseum.org/sites/default/…
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