Contents of the Winter 2015 Northants News

Dasylirion wheeleri                                        Colin C. Walker

             

Dasylirion is a genus that is not often encountered in cultivation in this country, because the plants are generally large-growing and hence not readily accommodated in pots in our usually smallish greenhouses.  The plants are drought tolerant or xerophytic rather than true succulents. The genus was first described in 1838 and now includes 22 species according to the latest survey (Hochstätter, 2011). It currently belongs to the family Ruscaceae or the Asparagaceae, depending on whether you adopt a narrow or broader view of families. Until recently it was part of the much smaller family, the Nolinaceae, that included just four genera, but as a result of recent molecular studies this family is no longer recognised. The most familiar genus closest to Dasylirion is Beaucarnea, of which B. recurvata, with its large swollen stem is a very common plant in cultivation, since it is often found for sale in garden centres (Walker, 2001).

Dasylirions are short perennial shrubs with thick unbranched stems crowned with dense rosettes of leaves with flowers on tall, thin spikes. The name Dasylirion comes from the Greek: “dasy” means “shaggy” and “lirion” is lily. This relates to the shaggy, unkempt appearance of the plants, in which old specimens have large numbers of dead leaves clothing the stem. Plants have a fountain-like arrangement of the long, narrow, flat leaves.

The key feature that characterises plants of this genus is that the leaf margins are usually prickly. The individual prickles can be straight, curved forward or recurved towards the leaf base. Some species have a mixture of different prickle arrangements and some have smaller prickles between the large ones. These prickles are vicious, giving the leaves the appearance and feel of small serrated kitchen knives that clearly deter animals from eating them!

Dasylirion wheeleri

Colin admiring Dasylirion wheeleri flowering in June at the Lady Bird Johnson Wildflower Center, Austin, Texas. 

Photo: Marjorie Thorburn.

The genus is distributed throughout Mexico as far south as Oaxaca, and north into the southwest USA in Arizona, New Mexico and Texas, but it is absent from California.

I encountered Dasylirion wheeleri in cultivation at the Lady Bird Johnson Wildflower Center in Austin, Texas. The species was named for Lieutenant G.M. Wheeler, who was leader of the geological and geographical survey of SW USA during which the species was discovered in 1875 in Arizona. It is now known to be one of the most widespread species, occurring in Arizona, New Mexico and Texas and south into Mexico (Sonora and Chihuahua), where it grows in grassland, open woodlands and scrubland. It reaches its eastern limit in the Franklin Mountains north of El Paso, Texas, where the plants are especially large and robust. It forms an attractive shrub with a single, unbranched stem up to 1.5 m tall with large numbers of arching, recurved leaves up to 1 m long but only about 2.5 cm across. The leaves are blue-green (glaucous) and nearly smooth, but as is typical for the genus, the leaf margins are armed with sharp, slender, straight to recurved prickles. The flower spike is slender and rises dramatically up to 4 m in height, as can be seen in the accompanying photo, and carries thousands of very small greenish-white flowers. Each plant produces only either male or female flowers and hence is described as being dioecious.

Dasylirion wheeleri

In cultivation the plant apparently has a tendency to rot in heavy soils and so requires good drainage.

Dasylirions have many uses and are commonly known by the Indian name of “sotol”.  The stems were used for building (posts in houses and corals) and for fuel. The leaves are trimmed off the stem and the remaining stump is roasted or boiled and then allowed to ferment to produce an alcoholic beverage, in much the same way that agaves are used to produce pulque, mescal and tequila. The leaves are much used for thatching, or are woven into mats or baskets, whilst the dried and varnished expanded leaf bases, so-called “desert spoons”, are used in flower arrangements.

Left: Rosette of Dasylirion wheeleri showing the long slender leaves armed with vicious prickles.

So, D. wheeleri is an attractive plant when it can be grown with unrestricted root room to enable it to reach its full potential. My own single potted specimen is merely a shadow of what it might become if it could be bedded out. I recommend this plant to those who have more space than I do. But be warned: if you ever encounter it, treat it gently because it bites back with a vengeance!

Finally, I thank Marjorie for the photo of me with a splendid specimen of D. wheeleri.

Colin

References

Hochstätter, F. (2011) Dasylirion Zucc. (Nolinaceae) Revisione del genere/Revision of the genus. 1-3. Piante Grasse 31(1): 25-30; (3): 106-122; (4): 162-181.

Walker, C.C. (2001) Dasylirion. In U. Eggli (ed.) Monocotyledons. Illustrated Handbook of Succulent Plants. Springer-Verlag, Berlin.

More on Dasylirion from Roland

Roland had a preview of this mag and noticed a blank space (in the printed edition). Now filled thanks!

Roland saw this flowering Dasylirion (right) at Kew. The information board noted that flowering is rare in the UK. Also the plant is dioecious and male flowers are white, females pink.

Kew commented that the flower spike was growing at a tremendous rate. Before the glass was removed, it grew nearly 50cm in 24 hours!

             

Dasylirion wheeleri at Kew

Dasylirion wheeleri at Kew

 

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