Crassula 'Tom Thumb' is the perfect succulent for miniature gardens, terrariums, and succulent projects! She is acutely aware of the interplay of colors and how they can be arranged to create a balanced look. Moon Cactus is a South American desert plant, mostly Argentina. Its shape and size can vary depending on the species. The succulents were larger than the rest, with the medium-sized ones just beyond that.