Mexican Jumping Bean
Arrow Poison Plant

Sebastiania bilocularis
(Sapium bilocularis)

Observed in the Ajo Mountains in western Pima County, Arizona, USA, March 2010. The reddish stalk is an old inflorescence now bare or fruit and flowers.

RANGE: Locally common at Organ Pipe Cactus National Monument and nearby mountain ranges. Rare or absent elsewhere in the USA. Common in Sonora and Baja California, Mexico.

SHRUB: A many branched woody shrub mostly about 2 meters tall but occasionally reaching 4 meters or taller. Twigs are reddish in color and when cut ooze a clear, toxic resin .

LEAVES: Leaves are dark green and lance shaped. The margins are mostly smooth with some faint dentitions. After cold weather or at ends of seasons leaves turn bright orange-red.

FLOWERS: Small greenish-red flowers on a spike. The flowers lack petals and are either male or female but occuring on the same plant, i.e. the plants are monoecious.

FRUIT: Three-valved capsule borne with with a large seed in each capsule. Some seeds contain a weevil larva that can cause the ‘bean’ to move or jump.

UNARMED

Euphorbiaceae -- Spurge Family

More Information:

• Southwest Environmental Information Network
• ITIS Taxonomic Report
• Cabeza Prieta Natural History Information
• USDA Plant Profile
• Google Images
• Google Scholar Literature Search
• Google Scholar w/ old name, Sapium biloculare