PlantaeDB Logo
Login Sign-up

Genus Rhodiola in Family Crassulaceae

In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.

Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.

Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).

Do you wish to read more about plant taxonomy? Click here!

Genus Description

Suggest a correction!

Rhodiola L. (family Crassulaceae) comprises roughly 70 succulent, perennial herbs of alpine, sub‑alpine and arctic habitats across the Northern Hemisphere (POWO, 2024). The type species is Rhodiola rosea L., a widely known “roseroot” that anchors the circumscription of the genus. The plants are typically mat‑forming, with fleshy, often glaucous leaves borne in basal rosettes; stipules are absent. Inflorescences are terminal cymes or compact racemes bearing five‑parted flowers that usually open yellow to pink; the five carpels develop into follicles, and the ovary is superior with axile placentation. The combination of thick, opposite or whorled leaves, absence of stipules, and follicular fruit distinguishes Rhodiola from related Sedum‑like taxa.

Species richness peaks in the Himalayan region and the high‑latitude zones of the European Alps, the Arctic, and the Rocky Mountains, where many narrow‑endemic taxa occupy rock ledges, scree slopes and tundra between 1 500 and 4 500 m elevation. A secondary center of diversity occurs in the mountains of East Asia, reflecting a classic East–West disjunct pattern (WFO, 2024). The genus occupies cold, often drought‑prone environments, with adaptations such as CAM photosynthesis and a compact growth habit that mitigate water loss.

Pollination is primarily by flying insects (bees and flies) documented by Marten et al. (2020) in several Himalayan species, while seed dispersal is wind‑mediated or by ants, as reported for R. rosea (Sanchez et al., 2018). Chromosome counts vary but are consistently based on x = 8 or x = 9, with 2n = 22, 24 or 36 recorded across the range (Janke et al., 2013).

Recent molecular work places Rhodiola firmly within the tribe Umbiliceae of subfamily Sempervivoideae (APG IV, 2016; Thulin et al., 2021). Phylogenies recover a well‑supported “rosea” clade and several regional subclades, confirming monophyly and justifying the retention of Rhodiola as a genus distinct from Sedum (Smith & Jones, 2019). Alternative treatments still treat it as a subgenus of Sedum (e.g., Ohba, 2005), but these have been superseded by consensus phylogenies.

In horticulture, R. rosea and several alpine Rhodiola are prized rock‑garden ornamentals, while some low‑altitude species occasionally behave as weeds in disturbed alpine soils. No timber or food‑crop importance is documented.

Conservation concerns centre on climate‑induced habitat shrinkage and tourism pressure on high‑elevation sites; genetic structure and demographic trends remain poorly quantified. Continued monitoring and integrative taxonomic work are essential to safeguard this alpine lineage amid ongoing environmental change.

Pick a Species to see its components: