Answer: I believe the plant you are referring to is Chamaelirium luteum, which is commonly called fairy wand, devil's bit or FALSE unicorn root, to distinguish it from true unicorn root, which is Aletris farinosa. You are right that male and female flowers occur on different plants. Female plants are usually leafier. If the plant is endangered as you state, there may not be a supply of them for the nursery trade; they may be difficult/expensive to grow to maturity in nursery conditions, or maybe it just hasn't been "discovered" as an appropriate landscape plant yet.
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