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There's tons of such sunflower-like asteraceae in the Americas but host is pretty certain yours is the common sunchoke or topinambur. Like with most crops, there's a ton of varieties bred for different purposes with varying tuber shape, size and color. In Germany it's mainly grown for liquor destillation but also animal feed and biofuel. It's healthy and has quite some potential but is invasive ans many don't like the taste and consistency. Also the tubers can't be stored for long. Don't know about California but in Europe it can only be harvested in autumn and winter. The tubers are hardy deep in the soil but while growing in spring and summer the plant exhausts the tubers so there's nothing to harvest. Only makes sense after the new tuber is formed in autumn. So it's a seasonal crop that's unavailable for half a year.
Have you tried sweet potatoes? They should grow in your climate. It's too cold here.