Introduction to Dasylirions (Sotols)
These are Yucca-like plants that include several commonly grown landscape species including the Mexican Grass Tree (Dasylirion longissimum), probably the most commonly grown Dasylirion. These American and Mexican plants also are vaguely reminiscent of Cycads having leathery to plastic-like thorny leaves and thick, palm-like caudeces/trunks. There are at least a dozen (some sources list up to 17) species of this genus though only 4-6 are regularly seen in cultivation. This article will cover these more common species and provide a few suggestions on how to take care of them.
The Dasylirions are closely related to the Agaves and were, until recently, in the same family (Agavaceae), along with Yuccas, Furcraeas and other Agave-like plants. But now they are in the Ruscaceae, a very similar family that includes Beaucarneas, Nolinas, Sansevierias and a few other seemingly completely unrelated genera of non-succulent plants.
Historically this plant was eaten (the caudex was cooked) and drunk (an alcoholic beverage called Sotol was made from the roots) and was a fairly important plant to the natives of the southwest US and Mexico. Now there are strictly landscape plants, prized for their amazing symmetry and durability (very drought and sun tolerant).
Dasylirion wheeleris in private garden used for landscape appeal
These are all pretty easy plants to grow if you have the right climate- hot and dry. I have little experience with these in cold or wet climates, but have seen a few do OK in fairly wet climates if the soil is very well draining. But they are prone to rot in such climates. They need very little water, but extra water is almost always appreciated as long as it's not directly on the crown (can cause rotting that way) even though rainfall does not seem to have the same deleterious effect as tap water on the crowns. These plants do well in pots, too, though they seem to grow a lot faster once large in the ground than in a pot (sometimes fast growth is not what one wants, though). Though drought tolerant, these plants will undergo some marked root shrinkage and die off in extremely dry, airy soil, making them less stable and easy to uproot (though this becomes less of a concern the older and larger the plants get). I have never fertilized mine, but I assume some fertilizer, particular water-based or very slow release would be fine. I just don't see the need for it.
My girlfriend's Dasylirion longissimum in a pot- one of her very favorite plants; old potted plant for sale, with a trunk that looks a lot like a cycad's
Rate of growth is about the same as a similar sized Yucca, but is much faster than other similar sized plants such as cycads or Xanthorrhoeas (Australian Grass Trees). Buying these as small one gallon-sized plants will not mean one will have to live with a one gallon-sized plant for many years as one would if purchasing a cycad or Xanthorrhea. This is particular true for Dasylirion longissimums which are very expensive as large plants (particularly trunking ones). A 1 gallon plant will be an impressive landscape plant in full, hot sun in the ground in just 3-4 years, and a trunking plant in another 5-7. A similar sized Xanthorrhoea (a very similar looking plant) can take many decades to become a decent landscape plant and I have no idea how long to form a trunk (certainly unlikely to see mine form one in my lifetime).
Dasylirion longissiumum (aka Dasylirion quandrangularis) first photo; Xanthorrhoea quadrangularis in second photo showing similarity; somewhat similar are some cycads like this Macrozamia johnsonii in the third photo
Flowers are solitary and either male or female (never both- therefore this is a dioecious genus of plants) and are quite tall and showy.
Dasylirion longissimum flower stalks showing buds in first photo, flowers in second and seeds forming in third (second photo by Chris Mankey)
Flowering plants: Dasylirion wheeleri (photo by kennedyh); Dasylirion berlandieri; Dasylirion longissimum
Dasylirion longissumum (sometimes called longissima or quadrangularis), aka the Mexican Grass Tree or Toothless Sotol, is unique among the Dasylirions (as least the common ones) by having grass-like leaves that are dull green, thin, 4 sided, toothless and up to 6' long. These plants from a ‘cush-ball'-like spherical head consisting of hundreds of leaves that come of the trunk in a very symmetrical array. These can be trimmed to a shuttle-cock shape exposing the ornamental trunk/caudex. This is probably the only really ‘user-friendly' species that can be planted safely along a high traffic walkway (though the leaf tips could potentially poke some hapless pet or child in the eye). If removing debris, such as fallen leaves from the crown, go slow... even though there are no teeth on the leaves of this species, the leaf blades are somewhat sharp and can slice open the skin if pulled against quickly.
Dasylirion longissimum specimen in nursery showing not all plants are single trunked; sky view of my own seedling; flowers of colony in Huntington Gardens, California
As mentioned already, this is a relatively fast growing species and eventually forms a trunk that can grow as tall as 15' (though this can take several generations). The trunks, if kept pruned and free of leaf bases are very ornamental being covered with a symmetrical pattern of leaf bases. The flowers of this species are similar to most other Dasylirions- huge, tall spikes (up to an additional 15'), solitary and covered with white flowers that open from striking red buds. Seeing a 15' specimen with a 15' flower spike is an impressive sight indeed.
15' tall plant with inflorescences at least another 10' tall; pruned landscape plant in private garden showing massive numbers of leaves this plant holds
This is a very popular species tolerating a wide variety of conditions including a modest amount of shade and humidity. They tend to get leggy in shady conditions, but tolerate them far better than any of the other species of Dasylirion, which tend to sulk and rot in such locations. I have personally not been able to overwater this species (as long as planted in well draining soil) and the more water they get, the faster they grow. They can tolerate as much heat as just about and climate can provide, and are cold tolerant to about 18F. Mexican Grass trees have been grown in England and New Zealand which I am not sure could be said about most of the other species in this genus (except perhaps Dasylirion acrotrichum). This species is from Northern Mexico.
Dasylirion longissimum leaf bases 'quadrangular' shape of leaves typical necrotic (dried out) leaf tips
Dasylirion wheeleri (Desert Spoon or Common or Blue Sotol) is probably the second most commonly grown species in cultivation. This species is native to Arizona and northern Mexico. It is immediately recognizable by its pale blue, usually somewhat twisted, flat, heavily armed, very stiff and narrow 3'-4' leaves that end in a brownish tassel. It is called a desert spoon because if the leaf if removed in its entirety the base of the leaf is spoon-shaped where it was attached to the caudex/stem. The leaves come off the caudex in a strikingly symmetrical pattern forming a perfect sphere of viciously sharp but ornamental leaves. This is NOT a good plant for near walkways as the leaves will readily grab all clothing or skin that rubs across them. I hate pulling fallen leaves from this plant as the leaves seem to reach and grab my arms no matter how carefully I reach in among them. I strongly recommend the use of thick gloves when pruning this plant!
Dasylirion wheeleri in botanical garden old plant in private garden (multiple trunks) my own seedling (about 5 years from seed)
This is a very sun and heat needy species, but is amazingly drought tolerant, even as a seedling. Plants grown in shade tend to be unhappy and eventually decline. I have not found these to be upset by excessively being watered as long as one does not excessively water the crowns. They just grow faster. I have not, however, attempted to discover their upper limits of water tolerance and suspect that there is one. Dasylirion wheeleris are cold tolerant down to below 15F and can tolerate brief periods of snow as long as the temps warm up soon after.
top view of my seedling showing tassels on leaf tips; leaf blade showing viscious spines (hooking in both directions); dried leaf tips
Dasylirion wheeleri flowers
This is an excellent potted plant and one of the best looking of all the Dasylirion species.
potted plant in private collection
Plant in my front yard... makes walking in shorts in this area a bit uncomfortable
Dasylirion texanum (Texas Sotol, or Green Sotol) is another somewhat common species in cultivation, but not one I can tell from Dasylirion acrotrichum (also known as the Green Desert Sotol). If one is roaming Texas and runs across a green Sotol, chances are it's this species since Dasylirion acrotrichum is from eastern Mexico. This species is not unlike Dasylirion wheeleri but distinctly a pale green color and the leaves are not twisted. Otherwise it is a very similar plant in both shape and size, and nearly as cold tolerant. Some populations, particularly in the very dry areas, are significantly smaller than most other Dasylirions having leaves only up to 2.5'-3' long. Leaves end in dry tassels much like they do in Dasylirion wheeleri (and most other spiny-leaved species).
Dasylirion texanums (mature plant, and my own seedling)
Dasylirion acrotrichum (or sometimes called Dasylirion acrotriche) (Green Desert Sotol, or Frayed Sotol) is a very similar though usually larger species to Dasylirion texanum. It is identically colored light, dull green leaves that are heavily armed with hooked spines and the leaves are relatively flat and wide. The leaves end in dried brown tassels for which the plant is named... but I cannot see what is unique about this as most of the other spiny-leaved species have similar frayed ends. I have seen photos of this species in England as well, so perhaps this species can tolerate more rainfall and humidity than some of the others. However I have no personal experience with this species.
Dasylirion acrotrichum (photo by GreenEyeGuru)
Dasylirion leiophyllum (Smooth Leaved Sotol) is another Texas native (but also grows in New Mexico as well as Mexico) and another pale green-leaved plant. Do not let the name smooth leaved give you the idea this is a toothless, user-friendly plant... it is just as viciously spiny as any of the other flat-leaved Dasylirions. Again, I am at a loss to tell this one from the above two... probably some minute floral variations. I know very little about this species other than it's less commonly grown than any of the above species.
Dasylirion berlandieri (Blue Giant Sotol) is somewhat unique in appearance in that is not only has some attractive, flat, relatively wide spiny blue-grey leaves, but the leaves are arching and less stiff than most of the other previously discussed species that tend have stiff, spherical crowns of leaves. Unlike most other flat leaved Dasylirions, the leaves of this species have no tuft at the end. As far as I can tell, this species also has the widest leaves of the ‘common' Dasylirions. It is native to the moderately high elevations in northeastern Mexico. I have only seen this species in the Huntington Gardens but it is certainly an attractive one though equally dangerous to walk near.
Dasylirion berlandieri in Huntington Botanical Gardens, California
Dasylirion glaucophyllum (Hidalgo Sotol) is sort of a halfway plant between Dasylirion wheeleri and Dasylirion berlandieri. This bluish species is similarly sized to Dasylirion wheeleri and has somewhat twisting heavily armed leaves, but these leaves have no frayed tips and they are somewhat droopy (not as stiff as in Dasylirion wheeleri). I have seen this plant grown in California, but I have never seen it for sale at any nurseries.
Dasylirion glaucophyllums in botanical garden
Dasylirion miquihuanensis (Arborescent Sotol) is a Mexican species with pale blue-green flat, stiff, narrow spiny leaves that forms a thick trunk up to 7' tall. It is not terribly unique in appearance but it is more readily available recently than some of the above species in cultivation. The leaves are slightly different in color than most of the other plants and the leaf tips end in a dried curling tuft that is perhaps less frayed than most. I am not sure why this species gets the name Arborescent Sotol when several of the other above species have trunks as well (though only Dasylirion longissimum seems to have one that is taller).
my own seedling of Dasylirion miquihuanensis leaf blade showing spines close up showing frayed leaf ends
Obviously there are more species out there, but I have either never seen them or heard of them. Many are so similar in appearance that I suspect there may be some synonymy that is not fully discussed or understood yet (certainly not by me at least). But this discussion should at least provide some with an introduction to these wonderful desert landscape plants.