So two weeks ago I took a class on California Native Medicinal plants at
Heather Farm in Walnut Creek taught by Tellur Fenner. An interesting class, just some bare bone basics, but we did learn how to use a few things.
One of the most surprising for me was making a cold infusion out of Fremontodendron californicum, also known as flannelbush.

Cold infusions are made by soaking something suspended in cheese cloth or muslin overnight, usually 1oz of an herb in 32oz of water.
Fremontodendron forms a mucous-like substance when soaked in cold water, which is good for coating the throat or esophagus, in other words for sore throats. We used the flowers, leaves and outer bark all dried and crushed or cut very small. You can use all three parts in combination or any of them individually. He said it was used similarly to slippery elm for those in other parts of the country.
I have to say as a gardener I don't really like this plant. Don't get me wrong, the plant is really beautiful, but I'm pretty sensitive to the little hairs on the leaves which make my skin itch and burn. It's very popular here in the Bay Area and people always seem to want me to prune one, or take it out or otherwise put myself in the middle of it. Fair enough, I suppose since they're paying me. And now that I know it can be used practically for sore throats I can appreciate again. If you are sensitive Tellur Fenner recommended straining it well, or I figure I can just use the flowers and bark.