By Wendy Langhans
What does Leonardo da Vinci, Vincent Van Gogh, the writers of the U.S. Constitution, the writers of the Dead Sea Scrolls and the Native Americans of southern California have in common?
They all used plant galls as a source of black dye.
Oak galls were used to produce iron-gall ink. To make the ink , oak galls were crushed to obtain gallotanic acid. Then the acid was mixed with water and iron sufate and exposed to oxygen. Gum arabic from acacia trees was added as binder, resulting in iron-gall ink. It had an advantage over carbon-based ink; iron-gall ink would not rub off of parchment .
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Native Americans used oak galls  as a source of dye for baskets, hair dyes and tattoos. They also made a decoction from galls to use as an eye wash, as well as a wash for wounds and sores.
But what, exactly, are oak galls? And how are they formed? According to an article  in “Natural History” magazine, “Plant galls are tumorlike swellings initiated mostly by insects”. They are found worldwide, in numerous plant species. Here’s just one example, an oak gall, found close to home in East/Rice Canyon. These galls, the largest found on oaks, are also known as “oak apples”, and are about 1-2 inches in diameter.
Many oak galls are produced by one of the 1,400 different species of cynipid wasps. Our local example was most likely produced by a California gallfly, “Andricus quercuscalifornicus”, which is actually a wasp. In the spring, the wasp lays an egg on an oak leaf. The oak responds by forming a small shell around the egg. But the gall growth really begins when the egg hatches and the larvae begins to chew on the plant. Their saliva stimulates the plant to grow the the gall, which provides food and shelter for the larvae until it is ready to hatch in October. Then it eats a hole through the shell and emerges. As the gall ages, it changes color from green to brown. Eventually, sometimes after several seasons, the gall falls to the ground and decomposes.
Galls provided healing for our wounds, Galls provided decor for our bodies and our useful, everday objects. And galls provided ink for our artists, our theologians and our founding fathers. All this - from the interaction between a wasp and a tree. Amazing.
Upcoming Outdoor Events:
Saturday, August 21, 8:00-10:00 AM. Morning Bird Hike at Towsley Canyon. Bring water and your binoculars and wear closed-toed shoes. Meet at the park entrance. 2 hours. For a map, click here .
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at firstname.lastname@example.org  for time and place.
Wednesday mornings, August 4, 11, 18 & 25.
Saturday mornings, August 14 & 28.
You can listen to stories like this every Friday morning at 7:10 a.m. on "The Hike Report", brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.