Habit: Shrubs, sometimes spreading by rhizomes; sparsely to densely stellate-hairy and simple-glandular-hairy, flowers sometimes also with simple or 2-branched nonglandular hairs; stellate hairs stalked or not, 3--40-branched; glandular hairs not branched, often << stellate hairs. Stem: erect to ascending. Leaf: petioled; blades ovate to round (rarely diamond-shaped or +- reniform), unlobed or 3--7-palmate-lobed, margins generally toothed, bases cordate to truncate or wedge-shaped; stipules awl-shaped or linear to lanceolate or sometimes curved; transitioning in inflorescence into bracts +- resembling stipules. Inflorescence: Head-like to spike-like to panicle-like; bracts subtending the often highly reduced inflorescence internodes awl-shaped to linear to triangular to +- round, sometimes curved, occasionally 2--5-lobed, if 2-lobed resembling fused pair of +- modified stipules, smaller bracts sometimes deciduous; bractlets in whorl of 3 subtending calyx, distinct (occasionally fused at base in M. aboriginum), generally awl-shaped to linear, occasionally oblong or narrowly elliptic to ovate, green or partially to all red. Flower: calyx 5-lobed, not enlarging after flowering, not inflated, lobes triangular to ovate, tips acute to acuminate; petals exceeding calyx, unevenly obovate with rounded tip entire to notched or somewhat ragged-margined, pink to occasionally white and often varying in populations, generally drying closed after pollination or in some taxa drying partially to fully open; stamen tube +- included, filaments terminal and subterminal; ovary of 7--14 carpels, ovules 1 per cell, styles 7--14-branched, branches equal in number to carpels, stigmas head-like. Fruit: +- disk-like, fragile when dry, tip minutely stellate-hairy; segments 7--14, drying tan, 1-celled, wide-elliptic to obovoid-reniform, often notched near base, smooth-walled, fully dehiscent with each fruit segment splitting into two separate halves, beak 0. Chromosomes: 2n=34.
Species In Genus: 21 species: California, Arizona, northwestern Mexico (Baja California). Etymology: (Greek: malakos, soft, thamnos, shrub) Note: Measurements for dry specimens; measurements for fresh specimens also provided in key. All Malacothamnus taxa can presumably hybridize; planting Malacothamnus taxa outside their natural range could threaten resident populations, a special concern for rare taxa. Hybridization/intergradation common where geographic ranges of some taxa meet; outside these zones of morphologically intermediate or intergrading plants, identification relatively simple and taxa relatively distinct. Such transition zones mostly between two taxa making parent taxa of intermediates easy to deduce; ranges of 3+ species abut near Santa Clarita making parentage of intermediate plants there unclear. Seeds generally germinate after fires in areas where woody plants burned; plants often short-lived, +- 5 years, but some may persist 20+ years post-burn.
Jepson eFlora Author: Keir Morse
Unabridged Reference: Morse 2023 Malacothamnus Volume 3 -- A Revised Treatment of the Genus Malacothamnus Based on Morphological and Phylogenetic Evidence https://doi.org/10.6084/m9.figshare.23937066
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)
Key to Malacothamnus

List of species Malacothamnus abbottii Malacothamnus aboriginum Malacothamnus arcuatus Malacothamnus arcuatus var. arcuatus Malacothamnus arcuatus var. elmeri Malacothamnus astrotentaculatus Malacothamnus clementinus Malacothamnus davidsonii Malacothamnus densiflorus Malacothamnus densiflorus var. densiflorus Malacothamnus densiflorus var. viscidus Malacothamnus discombobulatus Malacothamnus eastwoodiae Malacothamnus enigmaticus Malacothamnus fasciculatus Malacothamnus fasciculatus var. catalinensis Malacothamnus fasciculatus var. fasciculatus Malacothamnus fasciculatus var. laxiflorus Malacothamnus fasciculatus var. nesioticus Malacothamnus foliosus Malacothamnus fremontii Malacothamnus fremontii var. exfibulosus Malacothamnus fremontii var. fremontii Malacothamnus involucratus Malacothamnus jonesii Malacothamnus jonesii var. gracilis Malacothamnus jonesii var. jonesii Malacothamnus jonesii var. niveus Malacothamnus lucianus Malacothamnus marrubioides Malacothamnus mendocinensis Malacothamnus nuttallii Malacothamnus orbiculatus Malacothamnus palmeri

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