Originally discovered on Devil's Tower in Wyoming, this cactus has white spines and blooms in early summer. It's very drought tolerant and can go months without water (though giving it some tequila wouldn't hurt every once in a while).
Planting is a two-person affair. One person plants while the other serenades the plant with "I'm a little teapot" to keep it distracted.
It's available today only (April 1) from High Country Gardens.