The stems of this cactus are usually few in number, thin and barely succulent, to about 3 feet (1 m) tall. The plant grows from a large, starchy underground tuber that can occasionally weigh more than 40 pounds (18 kg). The nocturnal white flowers are about 3 inches (8 cm) across with very long floral tubes, and are strongly scented. (Some people can't smell them.) They close soon after the morning sun reaches them.