by Bruce Brethauer
The Agave Cactus is one of the most bizarre and unusual members of the cactus family: The plant produces a turnip-shaped root, with a compact stem from which arises numerous very long and thin tubercles - each measuring up to about 5 inches long and to about 1/2 inch wide. The tubercles are triangular in cross section, with the uppermost portion being flat, and the underside being deeply keeled. These taper gradually, but end abruptly at their tips with areoles which produce long, flattened paper-like spines, measuring up to 5 or 6 inches in length. Typical plants will grow to about 14 inches in height or less, but will occasionally grow to as much as about 30 inches tall. The plants are usually solitary, but some may occasionally tiller to produce a multi-stemmed plant. The species is native to the Chihuahaun desert in central and northern Mexico. While it has a fairly wide distribution, it is never common in any locality, typically having widely dispersed individual plants. In habitat, plants almost invariably grow in association with grasses, Yuccas, or Agaves, where their distinctive tubercles and paper-like spines help to camouflage them. Edward Anderson in his book The Cactus Family says it best when he says that only once had he found this plant in habitat when he was actually looking for it - every other time he found this plant was when he was searching for a different species, and he came upon this plant serendipitously: such is the effectiveness of this plant's mimicry. The fragrant flowers of this plant are large, to over 3 inches across, with attractive, satiny, pale-yellow petals. Individual flowers may only last 2 or 3 days each, but are typically produced in succession so that the total display may last intermittently through the summer months. Flowers arise from the areoles at the tips of young tubercles - mostly (if not exclusively) on the current year's growth. This species is closely related to Ferocactus, and plants of the two genera are sometimes hybridized - presumably producing some rather unusual looking hybrids.
Over the years, I have grown a number of plants of this species, and it has always been my experience that the lowermost tubercles ultimately die away, and eventually are lost, and the other tubercles will eventually suberize, producing flecks and patches of corky "bark"; I have yet to grow a "perfect" plant with unblemished stems and tubercles. I have observed other plants in cultivation, and this appears to be typical of most (if not all) mature plants of this species; it appears that growing the perfect "unblemished" plant is a virtual impossibility. This tendency may actually be set in this plants genes, as the marked stems and tubercles will help to camouflage these plants in habitat. As a result, any plant in cultivation will eventually develop the patina of a desert survivor which has seen its share of hard times - even if it has actually been pampered throughout its life - many growers like this appearance, but if you demand a plant with perfectly unmarked stems, then stay away from the Agave Cactus.
While field grown plants produced in the nurseries of Arizona and California can grow fairly rapidly - sometimes growing to fill a one gallon pot within a few years from seed - this does not match my own experience; here in Ohio - even when the plants are grown outdoors through the summer months, - the growth rate is considerably slower, with plants adding, at most, about 6 new tubercles each year and with the stems and roots barely increasing in diameter. While I'm certain that faster growing rates are possible here in Ohio, I am not certain what the secret is to growing a specimen sized plant quickly in my region without a greenhouse.
The 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, which is adapted to arid conditions, and seems to benefit from intense solar radiation. In my humble opinion, this plant 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 the increased temperatures of summer. Grown exclusively indoors, this species will slowly languish from the comparatively low light levels of interior spaces, and will probably never really thrive. Grown outdoors, this plant has proven to be a reliable bloomer, invariably producing intermittent blooms from late June through September. I am also convinced that by growing this plant outdoors through the summer months, is a bit more likely to tolerate 6 months of dormancy in a more dimly lit interior setting, especially if it is kept cooler and dry through the winter months. Despite its desert origins, my plants tolerate a remarkable amount of rain through their outdoor growing season, but due to their large, turnip-like roots, they can be very susceptible to root rot when exposed to extended cool and wet conditions, so the potting medium should be especially gritty to provide that extra drainage necessary for this species, and extra care should be given through the winter months to prevent over-watering this species. Many growers do not water this plant at all in the winter - I generally give my plant a light watering about once a month in winter to prevent root loss: but be warned, extended periods of cold and damp will rot this plant, so it is always better to err on the side of caution. This plant is also very frost tolerant, and will survive brief exposure to hard frosts (down to 10 degrees Fahrenheit according to Mesa Garden), but even though it will tolerate brief freezing conditions, I would recommend moving it to a warmer, protected area before subjecting this plant to frosts.
Leuchtenbergia principis is an exceptional plant which is particularly attractive to people who like some of the odder cactus species. Its leaf-like tubercles are practically unique to the cactus family, and its papery, tassel-like spines means that this plant presents little chance of injury to its grower. In time, plants will develop a desert-worn appearance which many growers favor. Best of all, I have found it to be a reliable bloomer, producing large, satiny, butter yellow colored flowers. This is a plant with lots of character, and unexpected beauty. To be fair, it may not be the perfect plant for the novice grower, but for those growers who do not mind catering a bit to the specific needs of their plants, this is an excellent choice.