I would be hard pressed to imagine a plant which looked more like something created by Dr. Seuss than the “Ponytail Palm”, with its large “Hershey Kiss” shaped caudex, long tapering trunk with its topknot of recurved, grass-
While most of us who are familiar with the “Ponytail Palm” as a houseplant, may think of it as a smallish shrub in cultivation, in habitat, it can eventually become a massive tree, growing to nearly 50 feet in height and producing a huge caudex up to about 10 feet in diameter. As the plant ages, it will tend to produce additional branches, forking here and there as the plant grows. In very large plants, many of the branches appear to arise directly from the huge caudex. Large specimens may produce several dozen individual branches, each topped with a characteristic topknot of recurved, pendulous leaves. The leaves are tough and very fibrous, and are narrow, growing from between ½ to 1 inch wide, and between 3 to 5 feet in length in larger plants (in younger, smaller plants, the leaves tend to be somewhat shorter). There is some variation in the degree to which these leaves curve: in some plants, the leaves are more rigid and are only slightly recurved, while in other plants, the leaves practically hang pendulously from the branches. The inflorescence grows to about 3 feet in length, and is covered with masses of tiny greenish to creamy yellowish flowers, each measuring to 1.5 to 3 mm across. The overall appearance of the inflorescence is reminiscent of an astilbe on steroids, and is very similar to those of Beaucarnea’s close relatives in the genera Nolina (Texas Bear Grass), and Calibanus hookeri. I have never seen a potted plant of the “Ponytail Palm” in flower, and speculate that this species will need to grow to a significant size before it will bloom. Male and female flowers are produced on separate plants, so to set seed, at least two plants, are required.
In Mediterranean climates around the world, the Ponytail Palm is frequently used in the landscape, where it is especially suited to dry soils, or soils with extremely sharp drainage. Large plants serve as a dramatic centerpiece in succulent and desert theme gardens. Locally, I know of two sites where large, mature specimens can be observed: the Franklin Park Conservatory maintains 2 large specimens in its desert biome and The OSU Biological Sciences Greenhouse Facility features 1 large plant in its collection.
Cultivated as a houseplant, the "Horsetail Palm" should be provided with a very bright window, preferably with a southern exposure, but this species will tolerate somewhat lower light levels: over the years, my own plant has been grown in an eastern, western, and southern exposure, and has grown well enough in each situation. Under less than ideal lighting conditions however, the growth rate of this plant will slow to a virtual crawl: brighter light will generally result in faster, stronger growth. My basic guidelines for growing succulents will apply to this plant; however, due to the size of this plant I have never moved it to a cooler growing area for a winter dormancy. While I may curtail water slightly through the winter months, I do not generally subject my plant to an extended drought at this time: as a result, it grows throughout much of the year, with a reduced rate of growth in the winter months. The "Ponytail Palm" should be given a gritty, but fertile potting medium; I use a mix of sifted garden loam, and Turface All Sport on my plant, but again, this plant will tolerate a variety of soils, and will probably grow well with any number of reasonably well draining soil mixes: avoid highly organic mixes which are designed to retain moisture for extended periods. This is another plant which should be moved outdoors to a sunny area during the summer months (gradually acclimating the plant to increased light levels to prevent leaf scorching). It will benefit from the increased light, temperatures, and exposure to summer rains. Spring and summer are also the best times to make applications of fertilizer -
In recent years, nurseries have added another species of the “Ponytail Palm”: Beaucarnea guatemalensis, has the reputation of being a faster growing plant, with a faster growing caudex. Initially, the caudex of this species is more spherical than that of Beaucarnea recurvata, but develops into a more slender and tapering caudex with age. B guatemalensis is ultimately a smaller plant, growing to under 30 feet tall and with a caudex growing to no more than 6 feet across. It leaves also tend to be somewhat wider and shorter than those of B. recurvata. There is also some speculation that B. guatemalensis may be more tolerant of lower light levels, and may therefore be better suited to the dimmer light of home interiors. At present, it is typically offered as a seedling plant, and is usually offered with a number of closely grouped seedlings each with a smallish "starter" caudex, or as a single plant, with a somewhat larger caudex, but with its trunk pruned so that the plant produces multiple branches. It seems to be becoming a very popular plant, and in time, I expect that the popularity of this species may exceed that of B. recurvata. Beaucarnea guatemalensis is a more tropical species, and is somewhat less cold hardy than B. recurvata. But you can hardly go wrong in growing either species as a houseplant, they are both undemanding, interesting, and long lived.