Nichols Turk’s Head Cactus Conservation

Reprinted from Cactus and Succulent Journal Vol. 79, No. 1, January-February 2007

Echinocactus horizonthalonius and its various subspecies are small barrel cacti whose distinctive blue-green coloration suggests the common name Blue Barrel. The plant has also been known as the Turk’s Head Cactus because of a fancied resemblance to a turban. With one exception it is a Chihuahuan desert species ranging from New Mexico, near Albuquerque (where a population was reportedly destroyed by development), south to west Texas and the Mexican states of Chihuahua, Coahuila, Nuevo Leon, Tamaulipas and San Luis Potosi. All varieties of E. horizonthaloniusare found in limestone-derived soils on hills or alluvial fans at elevations ranging from 2400 to near 5000’ and grow to a maximum 10-12 inches tall by 6 inches wide.

Nichols Turk’s Head (Echinocactus horizonthalonius var nicholii) is an interesting outlier, however, occurring at several isolated localities in the Sonoran desert of southern Arizona and northern Sonora, Mexico. In addition to its disjunct distribution, its flowers are a beautiful pink, as opposed to the range from red to white exhibited by the Chihuahuan Desert varieties. The Arizona plants all bloom on the same day, a characteristic that would appear to enhance the chances for successful cross pollination. They also tend to be cylindrical rather than globular in form, with a pronounced left or tight swirl to the ribs. Seeds often roll down the ribs and germinate at the base of the parent, which becomes a nurse plant for the seedlings, such that what appears to be a multi-headed plant is often actually several individuals.

Photos by Kathy Robertson, USFWS
Photos by Kathy Robertson, USFWS

The occurrence of a separate and distinct population separated by several hundred miles from the species’ primary range raises some interesting questions. Assuming the Arizona plants were originally introduced, how did they get here, and why didn’t they colonize apparently suitable habitat between the Waterman Mountains of Arizona and east central New Mexico? In Cacti of the Southwest W. Hubert Earle notes that several Chihuahuan desert species (including Epithelantha micromeris and Mammillaria heyderi) reach their western limits in the limestone hills of southeast Arizona. So why does Nichols Turk’s Head pass up this habitat for Sonoran desert lands far to the northwest?

Birds seem unlikely as a seed dispersal agent. Mature fruits are firmly encased in a cage of spines. Birds would have to work hard to get at the seeds and then fly a few hundred miles west to deposit them – a most unlikely scenario, indeed. Speculation that the Arizona plants were somehow introduced by early prospectors seems even more far fetched. Short of actually planting the seeds it is difficult to imagine any human activity serving as a dispersal agent.

A close look at the endangered Nichols Turk’s Head Cactus. One of only three known populations grows in the Waterman Mountains in the Ironwood Forest National Monument. They get their name from a spiral they develop as they grow taller, resemlbing a Turk’s turbine.Photo Carianne Campbell – Arizona Native Plant Society
A close look at the endangered Nichols Turk’s Head Cactus. One of only three known populations grows in the Waterman Mountains in the Ironwood Forest National Monument. They get their name from a spiral they develop as they grow taller, resemlbing a Turk’s turbine.Photo Carianne Campbell – Arizona Native Plant Society

A more likely explanation is that variety nicholii is a remnant of a once contiguous distribution that died out in the area between the present day populations, leaving what is known as a relictual distribution. The isolated population, no longer interacting with the more widespread populations farther east, is free to evolve separately, forming now a closely related, but distinct, variety.

A Desert Botanical Garden conservation report estimated the total number of E. horiaonthalonius var nicholii plants at 10,000 and recognized illegal collecting, off road vehicles, mining and erosion due to heavy foot traffic from drug- and people- smuggling as threats to the subspecies’ survival. It was listed as endangered in 1976 and is also protected by CITES (the Convention on International Trade in Endangered Species) and the Arizona Native Plant Law. An additional measure of protection was added with creation of the 129,000 acre Ironwood Forest National Monument by presidential proclamation in June 2000.

Resource surveys by the Bureau of Land Management have identified an even more insidious threat in the form of invasive weeds, especially Buffelgrass (Pennisetum ciliare). The devastating effect of invasive grass and weed-fueled fires in the Sonoran desert was graphically chronicled by Jan Emming in the Jan-Feb 2006 edition of Cactus and Succulent Journal.

Volunteers from the Sierra Club and the Arizona Sonora Desert Museum are determined to do everything we can to prevent Cave Creek-type fires from decimating Ironwood Forest National Monument. An abandoned air strip in the monument has provided ideal conditions for buffelgrass to spread into prime Nichols Turk’s Head habitat in the surrounding desert, and we have focused our initial efforts there. Our strategy has been to contain the spread o the grass by hand chopping, while management plans for the monument are completed and other control measures are evaluated. It is exhausting but rewarding work.

As a conservationist I have attended many meetings and written many letters, but the results of such activities are elusive and may take years to realize. But after a morning’s work at Ironwood, volunteers can reflect with pride on a truckload of Buffelgrass removed from sensitive habitat and take satisfaction in knowing that their efforts have made a difference. We can thank Sandy Bahr of the Sierra Club and Darrell Tersey at Bureau of Land Management for mobilizing forces to fight Buffelgrass; and Kathy Rice of the Desert Botanical Garden for technical advice.

With continued hard work and a little help we might eradicate this pest and save a beautiful and rare cactus. If you reside in Central or Southern Arizona we would very much appreciate your help.

Since this article was published in 2007, there has been a concerted effort to remove buffelgrass from the old airstrip at the base of the Waterman Mountains and from the Waterman Mountains themselves. Dedicated volunteers associated with many local organizations including the Friends of Ironwood Forest have contributed thousands of hours to removing this threat to the Nichols Turk’s Head cactus. The Friends of Ironwood Forest were awarded the 2010 Bureau of Land Management’s Making A Difference Volunteer Award and the Landscape Stewardship Award from the Public Lands Foundation.