Dasylirion longissimum
| Light | Full sun to bright light; tolerates some light shade |
|---|---|
| Water | Moderate in growth, drought-tolerant; allow to dry between waterings, keep drier in winter |
| Soil | Fast-draining gritty mix (see Soil and potting mix) |
| Temperature | Frost-hardy to around USDA zone 8b once established; protect from prolonged hard freezes |
| Propagation | Seed |
| Toxicity | Generally regarded as non-toxic, though leaf tips can be sharp |
Dasylirion longissimum is a slow-growing, trunk-forming succulent from the arid highlands of northeastern Mexico, grown for the dense, fountaining sphere of long, thin, smooth-edged leaves it carries atop a gradually lengthening stem. Unlike most of its relatives in the genus Dasylirion, its leaves lack the vicious marginal teeth that give sotols their reputation, which has earned it the common names Mexican grass tree and toothless sotol. Older plants raise their leafy crown on a thickening trunk, giving them the look of a green fireworks burst frozen in mid-air.
Description
Dasylirion longissimum forms a rounded rosette of extremely long, narrow leaves — often approaching a metre or more in length on mature plants — that radiate stiffly in every direction to build an almost perfect sphere. Each leaf is squarish or four-angled in cross-section (a feature reflected in its old name D. quadrangulatum), deep green, and, most distinctively for the genus, smooth along the margins rather than armed with hooked teeth. The leaf tips are firm and can be sharp, but the edges are safe to handle.
With age the plant develops a stout woody trunk, slowly lifting the crown of foliage well off the ground; large specimens can become imposing architectural plants over many years. Old leaves dry and skirt the trunk unless removed. Mature plants eventually send up a tall, narrow flower spike bearing many small flowers; like other sotols the species is dioecious, with male and female flowers on separate plants.
Distribution and habitat
The species is native to the arid limestone hills and desert scrub of northeastern Mexico, chiefly in the states of Tamaulipas, Nuevo León, San Luis Potosí and neighbouring areas. It grows in open, sun-baked terrain on rocky, sharply drained soils, enduring intense light, seasonal drought and considerable swings between hot days and cold nights.
Cultivation
Dasylirion longissimum is an undemanding, rewarding plant given the two things it insists on: strong light and sharp drainage. Grow it in full sun to very bright light in a gritty, free-draining mix, ideally in a pot only a little larger than the root ball. Water moderately through the warm growing season, letting the soil dry out between waterings, and keep it much drier and cooler over winter to avoid rot at the crown and stem base.
Established plants are notably tough and, once dry and dormant, tolerate light frost; in cultivation the species is often grown as a hardy architectural specimen to around USDA zone 8b, though prolonged hard freezes or cold combined with wet soil can be fatal. Container plants appreciate good air movement and benefit from being kept lean rather than pushed with heavy feeding, which only produces soft, floppy growth. See Watering and Repotting for general technique.
Propagation
Seed is effectively the only practical method. The species does not offset, so there are no pups to divide, and the single growing point means it cannot be increased by cuttings. Fresh seed sown on a warm, gritty, well-drained surface germinates over a period of weeks; because the plant is so slow, seedlings take several years to develop a recognisable rosette and much longer to form a trunk. See Propagation — seed for a full walkthrough. Note that fruiting requires both a male and a female plant, as flowers of the two sexes occur on separate individuals.
Common problems
- Rot — the most common cause of loss, almost always from overwatering, poor drainage, or cold wet conditions in winter; the crown or stem base softens and browns.
- Etiolation — too little light produces pale, weak, over-long leaves and a loose, floppy rosette that never forms a tidy sphere.
- Pests — mealybugs can hide down among the tightly packed leaf bases; scale is occasionally seen on the leaves. See Pests and diseases.
- Impatience — this is a genuinely slow plant; the fountaining sphere and trunk are the reward of years, not seasons.
See also
- Dasylirion — the genus overview
- Soil and potting mix · Watering · Repotting · Propagation — seed · Pests and diseases