A slow-growing, semideciduous succulent shrub with an upright form, this striking plant has a stout, gray, intensely spiny trunk that tapers at the base. Usually unbranched, it grows 4–6 feet tall in cultivation and up to 20 feet in its native habitat. Its narrow, glossy green leaves form a crown at the top, while 1–2-inch spines occur in groups of three. In spring and summer, mature plants produce fragrant 2–3-inch flowers with twisted white petals and yellow bases.