Dasylirion longissimum Seeds | Mexican Grass Tree

Mexican grass tree with a fountain of long narrow blue-green leaves on a short trunk — Mexican Grass Tree (*Dasylirion longissimum*): Asparagaceae, rocky slopes of northeastern Mexico.

LATIN NAME: Dasylirion longissimum

COMMON NAME: Mexican Grass Tree

Plant Profile

Mexican grass tree is a slow, sculptural plant of the high desert of northeastern Mexico, growing a stout, woody trunk one to two metres tall that is hidden for years by a dense head of leaves. The leaves are the longest in the genus: one to two metres of narrow, stiff, blue-green blade, only three millimetres wide, and completely without spines, so the head looks like a fountain of wire. Old leaves fall away to leave a neat skirt or a bare trunk, depending on the plant. It is dioecious, with male and female plants producing separate flower spikes two to three metres tall, covered in tiny cream flowers. It grows on dry, rocky slopes in Querétaro, Hidalgo and San Luis Potosí, where it may live for a century.

Science & Biotechnology

Dasylirion belongs to the Nolinaceae, the group of rosette plants in the Asparagaceae that includes Nolina and Beaucarnea, and its leaves are unusual in having no marginal teeth, unlike most of its relatives. The genus is being studied for its population genetics in Mexico, where several species are harvested for the fermented drink sotol, and the harvest of wild plants for the distillery has raised conservation concerns. The species is dioecious and wind-pollinated, and the seed set depends on having both sexes within a few hundred metres, which is a problem in fragmented populations. Its growth rate is extraordinarily slow, a few centimetres of trunk a decade, and a large plant may be older than the town it grows beside. Its leaves have a thick cuticle and sunken stomata, adaptations to heat and drought.

Uses & Benefits

The plant is grown as an architectural specimen in dry gardens, in large containers and in gravel plantings, where its fountain of stiff leaves and its eventual trunk make it a focal point. It is also used in xeriscaping and in commercial landscaping, where its tolerance of heat, drought and poor soil is valued. The leaves have been used for thatching and for weaving, and the trunk for small construction. Related species are distilled for sotol, though this one is not a main source. It is not a plant for a small garden or for rich soil, and it is very slow, so large specimens are expensive. It needs full sun, sharp drainage and room for the leaf spread.

Growing from Seed

Sow the seed in spring in a gritty mix of coarse sand, pumice and a little loam, one centimetre deep. Keep at twenty-five to thirty degrees with bright light; germination takes three to six weeks, and the seedlings are slow. Grow them in deep pots, since the plant makes a long taproot, and water sparingly. Plant out into a raised bed or a gravel garden with full sun and sharp drainage, and water only in the first summer. The plant tolerates frost to about minus eight degrees. Do not feed, and do not plant in a bed that receives regular irrigation, which rots the crown. Expect a metre of trunk in thirty years.

Our Take

A Mexican grass tree with metre-long spineless leaves and a century-long timetable. Full sun, gravel, and no hurry at all.

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