What can I grow that will be healthy for my ducks to eat?

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Question by brealyn71: What can I grow that will be healthy for my ducks to eat?
I can find a lot of information about plants to grow for feeding a home chicken flock, but what about for ducks? I am getting three buff orpington ducks to rotate through my garden, and I would really like to be less dependent on the feed stores, since they have to special order unmedicated food, and also for the joy of being able to care for myself with as little reliance on processing companies as possible. Any suggestions? Any links?
Of particular interest would be plants that are especially healthy or beneficial to ducks.

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