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Mexican Jumping Bean
Arrow Poison Plant

Sebastiania bilocularis
(Sapium bilocularis)

Sebastiania bilocularis, photo © by Michael Plagens

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.


Euphorbiaceae -- Spurge Family

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Copyright Michael J. Plagens, 1999-2010