Here's what the walnuts look like with their husks on. Ripe ones are yellowish and can be indented with your (glove-covered!) finger. Once they sit around on the ground or the hulls get smashed, they turn brown:
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I smash the hulls off by grinding them into the gravel driveway with my boots, or running over them with the car. Sushi cat for scale:
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As you may be able to see in this picture, the hull juices stain everything, including the plastic bucket and gloves. These are heavy-duty gloves. I made the mistake of wearing flimsy dishwashing gloves earlier, and ended up with stained hands for a week.
The walnuts dry outside for a while, then they sit on a window screen to "cure" for several weeks.
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Right now the nut meats are kinda rubbery. I tasted one and was blown away by its bitterness and fruity, almost apple-like, flavor. They say the flavor develops as the nuts cure. We'll see.