Ferocactus wislizeni

Name and identifying features

The accepted name is Ferocactus wislizeni. An older combination is Echinocactus wislizeni, under which the species was described in 1848. The spelling F. wislizenii also appears in horticultural literature. This account and the atlas index use wislizeni, following POWO. [2-WWW] [1-WWW]

The stem usually has 20–30 ribs, sometimes up to 40. The largest central spine is strongly hooked. Smaller, paler spines contrast with the massive central ones. Mature specimens often lean southwards. Together, these features help distinguish the species from F. acanthodes (called F. cylindraceus in many floras), whose older stems generally remain more upright. [Zimmerman and Parfitt 2003b, F. wislizeni description]

Distribution and habitat

The natural range includes Arizona, New Mexico, western Texas and northern Mexico. The floristic description lists desert scrub, grasslands and the lower margins of oak communities. Plants occupy plains, mountain foothills and slopes, often on deeper soils of limestone or igneous origin. [2-WWW] [Zimmerman and Parfitt 2003b]

Ecological studies were conducted at sites including Tumamoc Hill in Tucson. At this site, 259 plants growing at elevations of 750–900 m were observed. The local population is a well-studied example of interactions with ants, but the scope of the observations remains tied to its environment and the insects occurring there. [Ness 2006, p. 507–508]

Flowers, fruits and seeds

The flowers have a yellow, orange or red perianth. They develop near the stem tip, usually in late summer and autumn. The pale yellow fruits open at the base, releasing seeds. Their chamber remains dry. The seed surface has a fine, slightly raised reticulum, useful in identifying North American ferocacti. [Zimmerman and Parfitt 2003b, F. wislizeni description]

In the Santa Rita Experimental Range population, flowering was observed from mid-July to October. Flowers were 4.5–6 cm in diameter, and each remained open for 2–5 days. The stigma stood above the stamens and often served as an insect landing site. Nectar at the base of the short floral tube forced a bee collecting it to move through the surrounding stamens. [McIntosh 2005, p. 728]

Effectiveness of pollinating bees

McIntosh conducted experiments in 1996–1998. Flowers were covered with mesh before opening. A single visit was then allowed, the insect's identity and behaviour were recorded, the cover was replaced, and fruit formation was checked. This procedure linked a specific visit to its reproductive outcome. [McIntosh 2005, p. 729]

The most important pollinators were Diadasia rinconis, Svastra duplocincta and Ashmeadiella opuntiae. Single visits by D. rinconis more often resulted in a fruit. Fruits produced after its visits also contained more seeds than those following visits by S. duplocincta. Simply counting insects at flowers therefore overlooks differences in their services. [McIntosh 2005, tab. 2–3]

Fruits formed after a single visit contained a mean of 148 seeds, with a range of 2–951. Visits involving pollen and nectar collection did not differ significantly in seed number or fruit-set frequency. The plant's female reproductive success was assessed. Subsequent germination and offspring survival remained outside the experiment's scope. [McIntosh 2005, p. 730–733]

Nectar and four ant species

Modified spines in the upper areoles secrete nectar even outside the period when flowers are open. This allows ants to be present near buds and fruits. At Tumamoc Hill, the most common partners were Crematogaster opuntiae, Forelius sp., Solenopsis aurea and S. xyloni. A plant can host different species over the year, while simultaneous occupation by several species was rare. [Ness 2006, p. 507]

In experiments using a substitute herbivore, caterpillars of Manduca sexta, all four ant species recruited workers and attacked the introduced insect. Protection effectiveness depended on the species and number of ants. The abstract of the study by Ness and colleagues also describes a link between protection and maturation of reproductive organs. [Ness et al. 2006, abstract]

The most aggressive species, S. xyloni, often entered flowers. Bees visited plants attended by it less often and spent less time in each flower than on plants with less aggressive partners. These plants also had a lower seed mass per fruit. This was a comparison of natural partners, without random assignment of ant species. It reveals the co-occurrence of differences in protection, bee behaviour and reproduction. [Ness 2006, p. 511–513]

Petals also influenced ant behaviour. Workers of C. opuntiae avoided the half of a dish treated with a flower petal. This ant was relatively uncommon inside flowers. The test indicates the action of a signal from the petals, while the substance responsible for it was not identified in this study. [Ness 2006, p. 508–510]

Cultivation and seed production

The RHS recommends full sun and cultivation under glass, in a free-draining, peat-free, loam-based growing medium with added grit. Watering is moderate during growth. The medium remains dry during rest. A balanced liquid fertiliser is applied two or three times during the growing period. The horticultural profile also notes susceptibility to mealybugs. [1-WWW]

The RHS profile assigns the species to class H2, meaning it tolerates cold when protected from freezing. In Polish conditions, this means overwintering under cover. This horticultural classification describes care and differs in scope from experimentally determining tissue hardiness. [1-WWW]

Sowing is the main propagation method for such solitary specimens. Two genetically distinct plants are useful for producing one's own seeds, since studies show that successful reproduction depends strongly on pollen from another individual. Manual pollen transfer is described in the article on pollination, and the sowing process is explored in the sowing guide. [McIntosh 2005] [1-WWW]

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