Marshallocereus is a monotypic genus of flowering plant in the family Cactaceae. The only species is Marshallocereus aragonii that is found in Costa Rica, El Salvador, Guatemala, Honduras, Mexico, and Nicaragua.
Marshallocereus aragonii is a columnar cactus with dark green shoots that grow up to 5âÂÂ6 meters tall (rarely exceeding 6 meters) and 12âÂÂ15 centimeters in diameter. It branches minimally from the base and typically lacks a distinct trunk. The shoots often display a diagonal, light band pattern marking the end of annual growth. The plant features 5âÂÂ8 rounded ribs, 2âÂÂ3 cm high, with 1âÂÂ3 gray central spines (2âÂÂ3 cm long) and 5âÂÂ9 shorter marginal spines (up to 2 cm long). The funnel-shaped flowers bloom at night, measuring 6âÂÂ8 cm in length. They have greenish-brown outer bracts, white inner bracts, and a tubercled, thorn-covered pericarpel.
This species is native to northwestern Costa Rica, El Salvador, Guatemala, Honduras, Mexico (Chiapas), and Nicaragua growing in dry forests at elevations from 50 to 800 meters.
First described in 1902 by Frédéric Albert Constantin Weber as Cereus aragonii, it was named in honor of Manuel Aragon, a Costa Rican statistician. In 1951, Curt Backeberg reclassified it into the genus Marshallocereus, established the year prior. Common names include Guanocal, Organo, Pitahaya, and Tuna.