It's been raining here in California, a welcome respite from a long drought. Spring is thick with beautiful yellow oxalis blossoms, surprisingly appropriate to the garden in front of our hat factory. 

Oxalis is native to South Africa. Here it is referred to as an invasive species, a noxious weed, a pest plant -- and also as a tasty salad green with a bright lemony note. The bright citrus flavor is due to oxalic acid, which is lauded by some but can be dangerously unhealthy if consumed in quantity. And -- oxalic acid derived from the plant and diluted in water has long been used for removing stains and bleaching panama hats as recorded in the book Scientific Hat Refinishing, published in 1919.