Oaks have been an important and iconic fixture in my life. If you asked me to close my eyes and picture the land where I live, I would see oaks. And not just any oaks, but specifically Valley oaks, Quercus Lobata, with their tall stately trunks and the vast network of finger-like branches that crook as they reach for the sky. Valley oaks are widespread throughout the interior valleys and foothills of California, and they provide critical food sources for the caterpillars and other larvae of pollinators. As my dad is always reminding me, you can plant a million flowers in your garden to attract pollinators, but nothing is going to provide as big, or as important a food source for a diverse group of species, as an oak will.
Valley oak acorns also provided a staple food source for the indigenous people of this area. They ground acorns into flour and leached out the tannins to create a sweet and nutritious meal used for cooking. I haven’t taken the time to make my own acorn flour, although I hear it’s delicious, but instead I use the inedible tannins to make a beautiful dye that can then be shifted with iron to create a whole other set of colors. Acorns are best collected in fall once they have fallen to the ground. I’ve also collected acorns in early winter with good results, but after the rain arrives the acorns begin to germinate, and they aren’t great for dyeing anymore.
I also tested acorns from cork oaks, Quercus Suber. Cork oaks were introduced to California from their native habitat of the Mediterranean, where they thrive due to the similar climate and growing conditions. Cork oaks are used to make natural cork products like wine corks, although their use is declining due to synthetically produced substitutes. Cork oak acorns make a lovely range of colors. The tannins alone yield a nice strong butterscotch color, and when exposed to iron the tannins shift to a deep blue-purple.
I used the valley oak acorns whole, but crushed the cork oak acorns. I wondered if the results of the crushed acorns would be deeper because more surface area would be exposed for the tannins to leach out. Overall, the whole acorns seemed to perform just as well as the crushed ones. This was not a very scientific process considering I was comparing different acorns, and I gauged the results simply by eye. Perhaps at some point I’ll experiment with tighter controls, but for now my opinion is that unless you simply enjoy the tactile experience of crushing acorns ( My inner child certainly did!) it’s a task better left to making acorn flour.
There are so many species of oaks in this area, both native and introduced. After seeing how the cork and valley oak acorns differed, I’m eager to experiment with other oak species next year. I’m also eager to try oak bark as I’ve heard it yields a nice yellow. Have you worked with acorns, oak bark, or oak galls as dye? I would love to hear about your experiences if you give it a try. Sending you lots of acorn colored love wherever you are!