Aeonium arboreum 'Zwartkopf' is a beautiful succulent, up to 3 feet (90 cm) tall, that forms clumps of gray-brown stems that often branch near their base. The long bare stems hold large terminal rosettes, up to 8 inches (20 cm) in diameter, of very dark purple, almost black leaves. Flowers are yellow, star-shaped, and appear in summer in long, conical clusters from the center of the rosettes of mature plants, after which the stems bearing the flower die to the ground.