Selenicereus Testudo, also known as Dog Tail Cactus, is a unique lime green cactus with soft needles. Due to its epiphytic nature, it prefers more water (and even higher humidity) than most other species of cacti. You will notice it has small aerial roots which reach out into anything in their general vicinity. This cactus is an excellent choice for a hanging basket, with long trailing stems that come with maturity. For easy propagation, simply cut the stems at the joints and place in soil.