Eulychnia

Genus circumscription and names in older material

Plants of the World Online accepts nine species of Eulychnia. These are E. acida, E. breviflora, E. castanea, E. chorosensis, E. elata, E. iquiquensis, E. ritteri, E. taltalensis and E. vallenarensis. The genus occurs naturally in Peru and Chile. The name Philippicereus is its synonym in this classification. Accepted names and their circumscriptions were checked on 10 October 2026. [2-WWW]

In POWO, Eulychnia breviflora includes plants formerly called E. saint-pieana and E. barquitensis, among others. Stanton and colleagues' experiment on E. saint-pieana is therefore described in the atlas under E. breviflora, retaining the name used in the publication. [2-WWW] [Stanton et al. 2014]

Eulychnia ritteri (formerly also E. breviflora subsp. ritteri or E. iquiquensis subsp. ritteri) is an accepted Peruvian species. Historical subspecies treatments refer to the same lineage, for which modern accounts give distinct biology and range. [2-WWW] [Pauca-Tanco et al. 2021]

Eulychnia elata (formerly E. acida var. elata) is currently an accepted species. Its former varietal rank appears on phylogenetic trees from 2021. The authors retained original material labels without treating them as a taxonomic decision. [2-WWW] [Merklinger et al. 2021, p. 187–188]

Eulychnia chorosensis (formerly E. acida var. procumbens) is another separately accepted species. In contrast, the name E. procumbens Backeb., without a nomenclatural connection to Ritter's variety, is a synonym of E. breviflora in POWO. Rank and name author therefore also matter when identifying old labels. [2-WWW] [2-WWW]

Stems and flower structure

The genus includes multistemmed shrubs, forms with a distinct trunk and plants spreading low over the ground. Stems have longitudinal ribs with rows of areoles and spines. Growth form remains an important identification feature. The branched shrub E. breviflora, tree-like E. acida and widely spreading E. castanea represent different arrangements of columnar branches. [Merklinger et al. 2021, pp. 185–186] [Warren et al. 2016, pp. 185–186] [Warren et al. 2017, pp. 185–186]

Flowers are broadly bell-shaped. The lower part of the floral structure, called the pericarpel, may be strongly hairy or covered with spines. In Merklinger and colleagues' analysis, dense pericarpel hairiness was associated with the main lineage containing E. breviflora. The lineage containing E. acida had less hair or no visible hairiness, and some of its members bore spines. These features organise larger groups, but detailed species boundaries also require data on origin and variation. [Merklinger et al. 2021, p. 185–186, 191–194]

Cells strengthening the parenchyma

Stem parenchyma contains sclereids, cells with strongly thickened, lignified walls. The abstract of Nyffeler, Eggli and Leuenberger's study describes two types. In the outer green layer of the cortex, they are elongated and oriented perpendicular to the surface. Deeper in the cortex and in the pith, they are spherical or almost spherical and larger than surrounding parenchyma cells. Secondary walls form after cell growth ends. The authors propose that these structures contribute to mechanical stem reinforcement. [Nyffeler et al. 1997, abstract]

Coastal fog and rain farther inland

Many sites lie within the influence of ocean fog on coastal mountains. Vegetation occupies separate slope patches, between which extremely dry areas extend. In the north, differences in aspect and fog access strongly organise plant distribution. In the southern part of the range, seasonal rain becomes more important, and some populations extend farther inland. [Merklinger et al. 2021, p. 185–187] [Pinto 2007, p. 185–187]

In E. breviflora (called E. saint-pieana in the experiment), lichens on stems changed local temperature and vapour pressure deficit. Epiphytes intercept fog droplets but retain some of this water on their own surfaces. Their significance therefore involves both water input and its loss rate around the cactus. The full experiment is described in “Fog, lichens and water balance in Eulychnia breviflora”. [Stanton et al. 2014]

Reproduction and population renewal

In E. breviflora and E. acida, buds and flowers were shown to predominate on the northern, equator-facing side of stems. The authors propose a link with local assimilate production and flower warming. Studies of directional distribution describe reproductive geometry. Responses to water availability and the germination stage require separate experiments. [Warren et al. 2016] [Warren et al. 2017] [Piñones-Tapia et al. 2025]

The large fruits of E. acida are eaten by various animals, and seed fate depends on the consumer. In experiments, degus destroyed most swallowed seeds. Seeds recovered after passing through goats' digestive tracts retained germination comparable to the control. In Las Chinchillas reserve, young cacti were also associated with sheltered microenvironments beneath selected shrubs. Dispersal and subsequent seedling survival are successive stages studied separately. [Cares et al. 2018] [Cares et al. 2013]

Evolution of coastal lineages

DNA analyses from 2021 indicate that Eulychnia and Austrocactus are sister genera. Genomic data place the Peruvian E. ritteri as the sister lineage to the entire Chilean group studied. Dating reconstruction indicates recent, Pleistocene diversification of modern Eulychnia lineages. The authors hypothetically link it to alternating connection and isolation of habitats during moisture changes. Methods, uncertainty intervals and differences between genomes are explored in the article on evolution of the genus. [Merklinger et al. 2021, p. 190–194]

Cultivation in Poland

For container cultivation, the starting points are a bright position, ventilation and free drainage from a permeable growing medium. The RHS describes these general conditions for cacti. Watering during growth is combined with checking how dry the medium has become, and winter rest with less water. These are general cultivation principles under cover. Coastal fog data describe water access at a site and do not determine pot-watering frequency. [1-WWW] [Stanton et al. 2014]

An archival description of E. breviflora in Konrad Szychowski's private collection of materials gives a porous growing medium and restrained watering. It is retained in the species account and in profile P064. Scientific studies discussed under individual species supplement this material with ecology, flowering and germination. [Sukulenty b.d.a, skan, p. 4–6]

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