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Products > Dasylirion longissimum
Dasylirion longissimum - Mexican Grass Tree

[2nd Image]
Habit and Cultural Information
Category: Succulent
Family: Nolinaceae (~Agavaceae)
Origin: Mexico (North America)
Evergreen: Yes
Flower Color: White
Bloomtime: Summer
Synonyms: [D. quadrangulatum, Hort.]
Height: 6-10 feet
Width: 4-6 feet
Exposure: Full Sun
Summer Dry: Yes
Irrigation (H2O Info): Low Water Needs
Winter Hardiness: <15 F
Dasylirion longissimum (Mexican Grass Tree) A large evergreen trunk-forming shrub with fairly rigid 4 to 6 foot long glaucous-green grass-like long leaves. The leaves radiate symmetrically out of a large woody trunk that can slowly but eventually grow to 6 -15 feet tall. Not each year but generally summer to fall (occasionally in late spring), a nine foot tall spike of small white flowers emerge from reddish buds. Dasylirion are dioecious so are either male or female plants with the females often having decorative reddish seeds after flowering. Plant in full sun to light shade. Drought tolerant and cold hardy to at least 15 F. A great container plant or focal point specimen in the garden and on older plants the bottom leaves can be trimmed off to expose the trunk. Best to plant back away from a pathway; the leaves are not sharp but are rigid enough to be able to poke someone in an eye once they get to this height and leaf margins can slice like a paper cut. This species comes from the Mexican states of Hidalgo and Queretaro. The name for the genus comes from the Greek words 'dasys', meaning "dense" , "rough" or "shaggy" and 'lirion' meaning "lily" likely in reference to the rough leaves of some species. The specific epithet means "the longest" in reference to the extremely long leaves of this species. Also known at the Longleaf Sotol this plant was long been included in the Agave family (Agavaceae), but is now considered to be with Nolina and Beaucarnea in the Nolinoideae subfamily within the huge Asparagus family, the Asparagaceae. The scientific name of this plant has gone back and forth between Dasylirion longissimum and Dasylirion quadrangulatum. Generally these name have long been regarded as synonyms with Dasylirion longissimum, described in 1856 by the French botanist Charles Lemaire, considered to be the oldest valid name, while Dasylirion quadrangulatum was described in 1879 by the American botanist Sereno Watson. Most recently these plants have been determined to be two separate taxa that vegetatively look the same, but Dasylirion longissimum, the more southern occurring species from the Mexican states of Hidalgo and Queretaro, flowers later summer and fall with a spindle shaped inflorescence widest in the middle, while the more northerly species, Dasylirion quadrangulatum, from Tamaulipas, southern Nuevo Leon and northern San Luis Potosi, tends to flower earlier in the spring with a conical shaped inflorescence widest at its base. Since these plants were long considered synonyms, with seed collected somewhat indiscriminately, it is hard to know which plants are in gardens until they bloom. Rarely does a nursery plant flower and though we know that some of our older plants have previously flowered and these match best with Dasylirion longissimum, we cannot say the commercial seed purchased since had been the same and so might be either species. We feel this is consistent with plants sourced at other nurseries growing these narrow unarmed long leafed Dasylirion plants, so feel there is no guarantee which species one is likely to end up with. Fortunately both species look very much the same and visibly the differences are minor, so this should not be an issue for most, except those who maintain well documented botanical collections. There is a bit more about this on the Ruth Bancroft Garden's Dasylirion Page. We have grown this interesting and attractive plant at our nursery since 1988.  The information on this page is based on our research conducted in our nursery library, from online sources, as well as from observations made of this plant as it grows in our nursery containers, in the nursery's garden and in other gardens where we have observed it. We will also incorporate comments received from others and welcome getting feedback of any kind from those who have additional information, particularly if this information is contrary to what we have written or includes additional cultural tips that would aid others in growing  Dasylirion longissimum.