Scientific: Dasylirion quadrangulatum (formerly Dasylirion longissimum)
Common: Mexican grass tree, toothless sotol, longleaf sotol
Family: Asparagaceae (subfamily Nolinoideae)
Origin: Mexico in and around Coahuila, Tamaulipas, San Luis Potosi
Pronounciation: Da-sa-LIR-ee-on quad-ran-gu-LA-tum
USDA 7-10 (arid regions only)
Landscape Use: Specimen, textural accent, barrier, container plant for patios, xeric, oasis, or even mesic landscape design motifs
Form & Character: Large, upright, rosetting and rounded, wispy, airy, agave like, refined.
Growth Habit: Evergreen, perennial shrub, slow to moderate growth to 10- to 12-feet tall with 6-feet spread, caulescent. Flower spikes will extend to heights of 15 to 20 feet.
Foliage/Texture: Foliage densely-rosetting, long, very narrow (almost linear), dull to dark green to 3-feet long, leaves with unarmed simple margins; fine texture.
Flowers & Fruits: Dioecious, cream-colored flowers, plume-like, on a 10- to 15-feet stalk, plants will only flower after 7 to 10 years, and then will not flower every year thereafter.
Seasonal Color: Flowers stalks in later spring to summer.
Temperature: Tolerant of some heat stress above 110oF and is slightly more cold tolerant than Dasylirion wheeleri.
Light: Full sun
Soil: Well drained
Watering: Somewhat drought tolerant, some watering during the summer is needed if Mexican grass tree is planted in the lower desert urban landscapes, otherwise none. It's best to irrigate sparingly if at all during the winter. In the lower desert, it will typically show significant leaf tip necrosis.
Pruning: Only minimal pruning is generally ever needed. Minimal in this case means removing older dieing or dead leaves. If older dieing leaves are not removed then Mexican grass tree with develop a nice "grass skirt". Sadly, in many cases the improper planting of Mexican grass tree into small landscaped areas (spaces that are too small for this plant to grow to full size) will be the guiding motivation that 'horticulural clods' (aka 'hort clods') need to "prune" Mexican grass tree into one of their many classic Phoenix beer keg shapes.
Propagation: Usually propagated sexually by seed but germination and establishment are slow.
Disease and Pests: Root rot might occur if soil is chronically wet.
Additional comments: Mexican grass tree is a large, beautiful and noble plant for Phoenix landscapes. Like its counterpart Dasylirion wheeleri, Mexican grass tree is often misused by landscape designers in the Phoenix area, arranged in tight groupings without sufficient space for them to grow and spread naturally to full size.