Kalopanax (Castor Aralia)
Scientific Name: Kalopanax pictus
Family Name: Araliaceae
Tree: 40 50 ft. (12 -15 m) tall, with a round spreading crown. Mature castors have black bark with ridges, while saplings have green or yellow shoots with thorns.
Identifying characteristic: The large green star shaped and prickly leaves that give Castor a tropical appearance, identify it from other species.
Location: We found Castor Aralia growing in Cold Spring Park in Newton, Massachusetts.
History and Comments: Castor Aralia is native to Asia, and is highly invasive. It was introduced into the United States in the last 50 years, and it has just begun to infiltrate Cold Spring Park, where there are already several saplings growing. The threat from Castor is not yet fully recognized, and it is still recommended as a shade tree, because it is resistant to insects. However, when planted, it will seed in the neighboring areas and choke out native vegetation. It prefers wet areas, particularly by rivers, and it also needs a lot of sun.