Leuchtenbergia principis Hook.
Agave Cactus, Cob Cactus, Prism Cactus
Leuchtenbergia principis is a very slow-growing cactus with a cylindrical stem and long, slender tubercles. It is the sole species of the genus Leuchtenbergia. The stem becomes bare and corky at the base with age. It grows up to 28 inches (70 cm) tall. Tubercles are up to 3 inches (12.5 cm) long, grayish-green with purplish-red blotches at their tips, and topped with papery spines, making the plant resemble an Agave, hence the common name Agave Cactus. After four years or so, yellow flowers can be borne at the tip of the tubercles. The flowers are funnel-shaped and up to 2.4 inches (6 cm) in diameter. Fruits are smooth, green, up to 1.2 inches (3 cm) long, and 0.8 inches (2 cm) in diameter.
USDA hardiness zones 9a to 11b: from 20 °F (−6.7 °C) to 50 °F (+10 °C).
How to Grow and Care
Agave Cactus is a reasonably easy and tolerant plant and should grow well given the basic guidelines for growing cacti and other succulents. However, this is a desert species adapted to arid conditions and seems to benefit from intense solar radiation. Therefore, it should always be moved to a position outside during the warmer months of spring through early fall to benefit from exposure to direct sunlight and summer's increased temperatures.
Grown exclusively indoors, this species will slowly languish from the comparatively low light levels of interior spaces and will probably never really thrive. However, grown outdoors, this plant has proven to be a reliable bloomer, invariably producing intermittent blooms from spring to fall.
Agave Cactus tolerate a remarkable amount of rain through their outdoor growing season despite its desert origins. Still, their large, turnip-like roots can be very susceptible to root rot when exposed to extended cold and wet conditions. So, the potting medium should be especially gritty to provide that extra drainage necessary for this species. Also, extra care should be given through the winter months to prevent overwatering this species. Many growers do not water this plant at all in the winter.
Agave Cactus is usually propagated by seeds, as it rarely pups or has offsets. It has been reported that the plants can be propagated by tubercle cuttings, but this method is not common.
This species is native to north-central Mexico (San Luis Potosi, Chihuahua).
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