Malacothamnus (bush-mallow) is a genus of shrubs and subshrubs found throughout much of mainland California and on three of the Channel Islands. Outside of California, Malacothamnus is known from the northern half of Baja California, from a disjunct location in central Arizona, and possibly from a historic location that may have been in southern Arizona or adjacent Mexico. Plants of this genus are most commonly found in early-successional, post-burn plant communities.

Malacothamnus fasciculatus 2.jpg
Malacothamnus fasciculatus
Scientific classification e
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Malvales
Family: Malvaceae
Subfamily: Malvoideae
Tribe: Malveae
Genus: Malacothamnus

Thirty-seven Malacothamnus taxa have been described, but circumscriptions of many taxa are controversial due to overlapping morphological variation and limited analyses. At one extreme, Thomas Kearney recognized 28 taxa.[1][2] At the other extreme, David Bates who wrote the 1993 Jepson Manual and the Flora of North America treatments recognized only 11.[3][4] A more recent researcher of Malacothamnus, Tracey Slotta, recognized 17 taxa, reviving two species and four varieties subsumed by Bates.[5][6] Sixteen taxa are currently included in the CNPS Rare Plant Ranking system, with two presumed extinct.[7] Ten of these are not recognized under the Flora of North America treatment and six are not recognized under the most recent Jepson Manual treatment. Further research is currently in progress to resolve the taxonomy of the genus using both molecular and morphometric approaches.[8]

Malacothamnus are currently thought to be most closely related to the Iliamnas of the US interior and the Phymosias of Mexico, Central America, and the Caribbean.[5]

Species from treatments currently in use[1][2][6][4][9]


  1. ^ a b Kearney, T. H. 1951. “The Genus Malacothamnus, Greene (Malvaceae).” Leaflets of Western Botany VI (6):113–40.
  2. ^ a b Kearney, T. H. 1955. “Notes on Malvaceae VII: A New Variety in Malacothamnus.” Leaflets of Western Botany VII (12):289–90.
  3. ^ Bates, D. M. 1993. “Malacothamnus.” In The Jepson Manual: Higher Plants of California, edited by James C. Hickman, 751–754. Berkeley: University of California Press.
  4. ^ a b Bates, D. M. 2015. “Malacothamnus.” In Flora of North America North of Mexico, edited by Flora of North America Editorial Committee, 6:280–85. New York and Oxford.
  5. ^ a b Slotta, T. 2004. “Phylogenetics of the Malacothamnus Alliance (Malvaceae): Assessing the Role of Hybridization and Molecular and Morphological Variation in Species Delineation.” Ph.D. dissertation, Virginia Polytechnic Institute and State University.
  6. ^ a b Slotta, T. 2012. Malacothamnus. In B. Baldwin, D. Goldman, D. Keil, R. Patterson, T. J. Rosatti, and D. H. Wilken [eds.], The Jepson Manual: Vascular Plants of California, 884–885. University of California Press.
  7. ^ "CNPS Inventory of Rare and Endangered Plants: Malacothamnus"
  8. ^ Morse, K. "Malacothamnus - The Bush-mallows"
  9. ^ Morse, K., and T. Chester. 2019. Malacothamnus enigmaticus (Malvaceae), a new rare species from the desert edge of the Peninsular Range in San Diego County, CA. Madroño 66: 103–119.

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