These cycads resemble Cycas revoluta, but they are less widely sold, more tender, and even slower growing. Male and female plants are separate. Dioons are excellent choices for tropical effects and as container plants. Native to the American tropics, these living fossils have changed little in 200 million years. Not browsed by deer.
D. edule. VIRGIN PALM. Zones LS, CS, TS; USDA 8-11. Very slow growing. Eventually forms cylindrical trunk 610 in. wide, 3 ft. high. Spreading, slightly arching, 3- to 5-ft. leaves are made up of many leaflets that may be toothed at the tips or smooth edged. Foliage on young plants is dusty blue-green and feathery; that on mature plants is deeper green, shiny, more rigid. Established plants tolerate temperatures to 15F.
D. spinulosum. Zones TS; USDA 10-11. Slow growth to 12 ft. Leaves reach about 5 ft. long, with up to 100 narrow, spine-toothed, dark green, 6- to 8-in.-long leaets. Protect plants from frost.