Ferocactus acanthodes

Name and subspecies circumscription

POWO accepts Ferocactus acanthodes and three subspecies. These are the nominate subspecies F. acanthodes subsp. acanthodes, subsp. eastwoodiae and subsp. lecontei. The name Ferocactus cylindraceus, common in articles and floras, is a synonym of the nominate subspecies in this database. Flora of North America retains a different treatment and uses F. cylindraceus. The appropriate names accompany the descriptions of individual studies here. [2-WWW] [2-WWW] [Zimmerman and Parfitt 2003b]

The former names F. cylindraceus subsp. lecontei and subsp. eastwoodiae correspond to separate subspecies in the current classification. Information on locality and original identification therefore remains part of the result. Updating the name of plants from a given population preserves their scope, while physiological data from one region require separate verification in other subspecies. [2-WWW]

Structure and identification

The stem is usually upright and elongated. The Flora of North America description generally gives a height of 45–150 cm and a diameter of 25–40 cm, with some specimens outside these ranges. The ribs are distinct, with a small notch above the areole. The largest central spine is curved or twisted, and a strong hook is more common in young plants. [Zimmerman and Parfitt 2003b, F. cylindraceus description]

The flowers are usually yellow inside and darker outside. The pale yellow fruit opens through a hole at the base. The seed surface is pitted. Stem, spine and seed features considered together help distinguish the plant from F. wislizeni. [Zimmerman and Parfitt 2003b, F. cylindraceus description]

Range and habitat conditions

The natural range includes southern California, Arizona, Nevada, southwestern Utah and northwestern Mexico. The flora describes plants from the Mojave and Sonoran deserts and dry scrub, often on rocky slopes with igneous or limestone substrates. It gives elevations from sea level to 1500 m. [2-WWW] [Zimmerman and Parfitt 2003b]

A flower open to specialised bees

At Desert Peak, northwest of Tucson, plants studied as F. cylindraceus flowered from late April to September. Flowers in this population were 3.8–6 cm in diameter and remained open for several days. Nectar was secreted at the base of the short floral tube, and the raised stigma often received the landing insect. [McIntosh 2005, p. 728–729]

In 1996–1998, the dominant visitor and pollinator was Diadasia rinconis. Across the three seasons, 25, 70 and 113 visits respectively were recorded for this species. The counts reflect different observation effort in successive years, rather than a direct change in bee density. A single visit, when it resulted in a fruit, yielded a mean of 149 seeds, with a range of 11–896. [McIntosh 2005, tab. 1, p. 730]

Bees collecting nectar and pollen achieved comparable fruit-set and seed-production results. The largest contribution from D. rinconis arose mainly from frequent visits. Specialisation defined this way is a feature of the ecological system studied, involving one population and observations from about 9 to 13 h. Other sites may have different insect communities. [McIntosh 2005, p. 730–733]

Cultivation and propagation

For potted plants, the starting point is a bright, airy position under cover and a free-draining growing medium. Water during active growth, after checking how dry the mix has become. Water drains from the pot. A cooler, drier winter rest and abundant light support flowering. These are general RHS recommendations for indoor desert cacti. [1-WWW]

Reproduction in the population studied depended on seeds and cross-pollination. When planning to sow one's own seeds, pollen can be transferred between genetically distinct flowering individuals. The single-visit experiment highlights the importance of actual contact with floral organs and subsequently checking whether a fruit forms. [McIntosh 2005]

Roots during drought

North and Nobel's experiment used F. acanthodes from Agave Hill near Palm Desert in California. At the onset of drought, root segments were around one, three and twelve months old. The youngest retained a surrounding sheath of root hairs, mucilage and soil particles. It protected the tissues from drying. Three-month-old roots developed lacunae, spaces left by ruptured cells of the primary cortex. In the oldest roots, the authors assigned an important role to dehydration of the periderm, a secondary protective tissue containing suberin. [North and Nobel 1992, p. 10, 13–14, 18]

After 30 days of drought, at a soil water potential of around −3.5 MPa, hydraulic conductivity in three-month-old ferocactus roots was reduced by 61%, and in twelve-month-old roots by 57%. After rewetting, young roots recovered almost their initial conductivity. Older roots returned to only part of their maximum value. Reversible embolism, interruption of the water column by gas, occurred in vessels in all groups. However, reduced performance of the whole root also remained related to barriers along the path from its surface to the xylem. [North and Nobel 1992, pp. 13–18]

Conductivity was measured on excised roots immersed in a solution, so it describes tissue properties with water contact assured. In the habitat, root contact with soil also matters. Shrinkage during drought can create air gaps that increase resistance at this interface. The results concern the Californian material studied, associated with the nominate subspecies. The experiment did not compare the physiology of all subspecies of F. acanthodes. [North and Nobel 1992] [2-WWW]

Ribs added during growth

Rib number can change as a plant grows. Robberecht and Nobel studied 100 randomly selected F. acanthodes at Deep Canyon in California. In 56% of the plants, the number of ribs halfway up the stem was 5, 8, 13 or 21. These are successive Fibonacci numbers, each being the sum of the preceding two. A further 19% had a number differing by one from such a value. The pattern described the structure of the population studied, which also included plants with intermediate values. [Robberecht and Nobel 1983, p. 153–154]

New ribs appeared first near the tip. Their number at the top could therefore exceed that in the middle of the stem, while remnants of an earlier arrangement persisted at the base. Some plants had 21 ribs at the top, 13 in the middle and 8 at the base. The authors linked the stepwise addition of ribs to stem development and the ability to change its volume as hydration fluctuates. The causes triggering successive stages were not determined experimentally in this study. [Robberecht and Nobel 1983, pp. 153–155]

Related articles

Materials from the author's archive

The species also appears in Konrad Szychowski's private material archive. [Kaktologia 2009b, file p. 9] [Neciu b.d., file p. 1] [Romulski b.d., file p. 8]