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Key to MalacothamnusView taxon page for Malacothamnus
(For a list of species in Malacothamnus, use the above link.) Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots. Key to Groups: Estimated measurements for fresh, rather than dry, material included in curly brackets {} and underlined. Key based on flowering and fruiting specimens with stem hairs measured from first internode below inflorescence. Known introductions of taxa outside natural ranges are considered in key; consult maps of geographic ranges of taxa when making identifications. If specimen is from a transition zone between taxa, it may be morphologically intermediate and not key well; notes helpful in identifying some intermediates available in descriptions of parent taxa.
5. Plants of s SCo, PR, and DSon of Orange, Riverside, and San Diego cos. ..... Group 5 6. Plants of n SCo, TR, and s DMoj in southern Kern, Los Angeles, southern San Bernardino, and Ventura cos. plus south and west edge Santa Barbara Co. ..... Group 6 6' Plants of SCoR and adjacent SnJV and s CCo in western Fresno, Monterey, San Benito, and San Luis Obispo cos. plus Santa Barbara Co. except south and west edge ..... Group 7 Group 1: Plants of ChI1. Stem stellate  Pertaining to a hair or other structure with three or more branches radiating in two or three dimensions from a common point. hairs with branches <= 2 mm (mean per plant 0.5–1.2 mm); s ChI (San Clemente Island) ..... M. clementinus 1' Stem stellate hairs with branches <= 0.8 mm (mean per plant 0.1–0.3 mm); other islands
Group 2: Plants of SN and adjacent e SnJV, s SNE, and n DMoj 1' Corollas drying closed after flowering; west or east of SN crest 2. Bractlets subtending calyx 6–14(18) {7–17(21.5)} mm, >= 0.6× calyx; flower buds  1. An incompletely developed, more or less embryonic shoot, usually covered with bud scales. 2. An unopened flower, often protected by sepals. clearly pointed; most stellate Pertaining to a hair or other structure with three or more branches radiating in two or three dimensions from a common point. hairs unstalked; leaves and inflorescence often ± sticky from glandular hairs; leaf  Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets). bases truncate  Abruptly (not gradually) narrower or smaller at base or tip, as if cut straight across or nearly so. to cordate  Heart-shaped; often pertaining to a leaf in which the blade base on both sides of the petiole is rounded and convex. ; in this region only known from one 1800s collection near Millerton Lake (c SNF) ..... M. marrubioides (G6) 2' Bractlets subtending calyx 2.5–8 {3–9.5} mm, <= 0.8× calyx; flower buds generally rounded to slightly pointed, occasionally clearly pointed; many stellate hairs with stalks; leaves and inflorescence generally not sticky; leaf bases generally cordate (rarely truncate to oblique); east of SN crest and west of crest south of Springville ..... M. orbiculatus (G6, G7)
Group 3: Plants from NW, CaR, ScV1. Bractlets subtending calyx <= 2 {2.5} mm; abaxial calyx stellate Pertaining to a hair or other structure with three or more branches radiating in two or three dimensions from a common point. hairs with branches <= 0.2 mm; Mendocino Co. ..... M. mendocinensis 1' Bractlets subtending calyx >= 3 {3.5} mm; many abaxial calyx stellate hairs with branches > 0.2 mm; other counties 2. Calyx lobe  1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth. width at widest point >= 1.4× width at lobe base, lobe edges obviously protruding in bud  1. An incompletely developed, more or less embryonic shoot, usually covered with bud scales. 2. An unopened flower, often protected by sepals. ; Shasta and Tehama cos. ..... M. astrotentaculatus 2' Calyx lobe width at widest point <= 1.2× width at lobe base or widest at base, lobe edges not obviously protruding in bud; Tehama Co. and south 3. Stem stellate hair branches <= 0.6 mm (mean per plant 0.1–0.4 mm); leaf Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets). bases often subcordate to obtuse  Having a short-tapered, blunt tip or base, the sides convex or straight and converging at more than a right angle. , occasionally cordate Heart-shaped; often pertaining to a leaf in which the blade base on both sides of the petiole is rounded and convex. or wedge-shaped ..... M. fremontii var. exfibulosus 3' Stem stellate hair branches <= 1.4 mm (mean per plant 0.3–0.7 mm); leaf bases often cordate, occasionally truncate Abruptly (not gradually) narrower or smaller at base or tip, as if cut straight across or nearly so. to obtuse ..... M. fremontii var. fremontii (G2, G4)
Group 4: Plants of SnFrB and adjacent n SnJV, n CCo, and n SCoRI1. Corollas drying partially to fully open; calyx lobes 1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth. >= 6 {7} mm ..... M. fremontii var. fremontii (G2, G3) 1' Corollas drying closed; calyx lobes < 6 {7} mm 2. Leaf blades generally moderately 3–7-lobed, lobes acute  Having a short-tapered, sharp tip, the sides convex or straight and converging at less than a right angle. (rarely obscure or rounded); stellate Pertaining to a hair or other structure with three or more branches radiating in two or three dimensions from a common point. hair branches on leaf Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets). blades mostly <= 0.2 mm; commonly planted ..... M. nuttallii (G6, G7) 2' Leaf blades unlobed or obscurely (rarely moderately) 3–5-lobed, lobes rounded to approaching acute; stellate hair branches on leaf blades mostly >= 0.2 mm; native to this region ..... M. arcuatus 3. Calyx-subtending bractlet length >= 3 {3.5} mm, >= 1/2 of calyx length; branches of stellate hairs on stem often distinct without magnification, longest stem hair branches generally > 0.5 mm ..... M. arcuatus var. arcuatus 3' Calyx-subtending bractlet length <= 3.5 {4} mm, <= 1/2 of calyx length; branches of stellate hairs on stem generally not distinct without magnification, longest stem hair branches generally <= 0.5 mm ..... M. arcuatus var. elmeri
Group 5: Plants of s SCo, PR, and DSon in Orange, Riverside, and San Diego cos.1. Inflorescence a narrow to wide panicle  1. In flowering plants excluding Asteraceae, Cyperaceae, Poaceae, and some other groups, a branched inflorescence in which the basal or lateral flowers (or some of them) open before the terminal or central flowers on any axis. 2. In Asteraceae, Cyperaceae, Poaceae, and some other groups, a panicle-like inflorescence is one in which at least some of the inflorescence units (e.g., heads in Asteraceae; spikelets in Cyperaceae and Poaceae), instead of individual flowers, are attached (stalked or unstalked) to branches and not directly to the main axis of the inflorescence and in which floral development may or may not proceed as in 1. 2. Stellate hairs on calyx with most branches <= 0.2 mm; native north of San Diego Co. and possibly near its northern border, planted elsewhere in county ..... M. fasciculatus var. laxiflorus (2; G6) 1' Inflorescence spike-like, occasionally with axillary  Pertaining to or within an axil, especially a leaf axil. spikes near base of inflorescence 3' Most glandular hairs on stem <= 0.1 mm and all <= 0.3 mm, all glandular hairs on abaxial calyx <= 0.4 mm; abaxial calyx tube densely to sparsely stellate-hairy 4. Abaxial calyx tube generally with sparse stellate Pertaining to a hair or other structure with three or more branches radiating in two or three dimensions from a common point. hairs and/or simple  Composed of a single part; undivided; unbranched. to 2-branched nonglandular hairs; calyx stellate and 2-branched hair branches <= 4 mm (mean per plant 0.5–2.3 mm) ..... M. densiflorus var. densiflorus 4' Abaxial calyx tube with dense stellate hairs; calyx stellate hair branches <= 2 mm (mean per plant 0.1–0.6 mm) 5. Calyx lobes 1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth. 3–12 {3.5–14.5} mm; bractlets subtending calyx 3–13 {3.5–15.5} mm; bracts subtending inflorescence internodes  Segment of an axis (generally a stem) between successive positions (nodes) from which one or more structures (especially leaves, buds, branches, or flowers) arise. within and just below flower clusters (0.5)1–8(12) {(0.5)1–9.5(14.5)} mm wide, most easily seen near the base of immature flower clusters; desert transition zone, San Diego Co. ..... M. enigmaticus 5' Calyx lobes 2.5–5 {3–6} mm; bractlets subtending calyx 1–5 {1–6} mm; bracts subtending inflorescence internodes within and just below flower clusters 0.5–2.5(4) {0.5–3(5)} mm wide; elsewhere 6. Longest stellate hair branches on stem below inflorescence and on calyx >= 0.3 mm (mean per plant 0.1–0.4 mm); near northern border of San Diego Co. and south to Baja California ..... M. fasciculatus var. fasciculatus 6' Longest stellate hair branches on stem below inflorescence <= 0.4 mm (mean per plant 0.1–0.2 mm), longest stellate hair branches on calyx <= 0.5 mm (mean per plant 0.1–0.2 mm); near northern border of San Diego Co. and north, some planted in San Diego Co. ..... M. fasciculatus var. laxiflorus (2; G6)
Group 6: Plants of n SCo, TR, and s DMoj in southern Kern, Los Angeles, southern San Bernardino, and Ventura cos. plus south and west edge Santa Barbara Co.1. Calyx lobes 1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth. 3–9.5 {3.5–11.5} mm wide, lobe 1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth. width at widest 1–6× width at lobe base; known in this region only from Aliso Canyon Park (Los Angeles Co.) ..... M. foliosus 1' Calyx lobes 1.5–4 {2–5} mm wide, lobe width at widest 1–1.5× width at lobe base 2. Bractlets subtending calyx <= 1/2 calyx length; branches of stellate Pertaining to a hair or other structure with three or more branches radiating in two or three dimensions from a common point. hairs on stem and calyx average 0.1–0.2 mm 3. Leaves generally bright green adaxially (occasionally gray-green), paler abaxially; adaxial leaf Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets). stellate hair branches 0.1–0.4 mm, uneven in size – scattered hairs with longer branches than most; mostly south of Santa Clara River and/or east of Santa Paula, one presumably planted population to west near Lake Casitas ..... M. fasciculatus var. laxiflorus (G5) 3' Leaves pale gray-green to light green adaxially, not or slightly paler abaxially; adaxial leaf stellate hair branches 0.1–0.2 mm, even in size; mostly north and west of Santa Clara River and west of city of Santa Paula, commonly planted elsewhere ..... M. nuttallii (G4, G7) 2' Bractlet or stellate hair branch lengths not as stated above 4. Bractlets subtending calyx 6–14(18) {7–17(21.5)} mm, >= 0.6× calyx; flower buds 1. An incompletely developed, more or less embryonic shoot, usually covered with bud scales. 2. An unopened flower, often protected by sepals. clearly pointed; most stellate hairs unstalked; leaves and inflorescence often ± sticky from glandular hairs; leaf bases truncate Abruptly (not gradually) narrower or smaller at base or tip, as if cut straight across or nearly so. to cordate Heart-shaped; often pertaining to a leaf in which the blade base on both sides of the petiole is rounded and convex. ..... M. marrubioides (G2) 4' Bractlets subtending calyx 1.5–8 {2–9.5} mm, <= 0.8× calyx; flower buds generally rounded to slightly pointed, occasionally clearly pointed in M. orbiculatus; many stellate hairs with stalks; leaves and inflorescence generally not sticky; leaf bases generally cordate 5. Bractlets subtending calyx 1.5–4.5 {2–5.5} mm; calyx lobe length generally 1–2.3× width; plants generally 1–5 m; San Fernando Valley, nearby southern slopes of SnGb, and Verdugo Mountains ..... M. davidsonii 5' Bractlets subtending calyx 2.5–8 {3–9.5} mm; calyx lobe length generally 1.4–4× width; plants generally <= 2 m; northern slopes of SnGb and SnBr and north ..... M. orbiculatus (G2, G7)
Group 7: Plants of SCoR and adjacent SnJV and s CCo in western Fresno, Monterey, San Benito, and San Luis Obispo cos. plus Santa Barbara Co. except south and west edge1. Inflorescence head-like, occasionally with second (generally smaller) flower cluster below terminal cluster 2. Many branches of stellate Pertaining to a hair or other structure with three or more branches radiating in two or three dimensions from a common point. hairs on stem 1–3 mm; many simple Composed of a single part; undivided; unbranched. glandular hairs on stem, leaves and abaxial calyx 0.3–1.4 mm, generally distinct at 20× magnification, occasionally sparse and difficult to detect; stem surface and abaxial calyx lobe 1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth. surface generally easily visible through hairs without magnification ..... M. lucianus 2' Most branches of stellate hairs on stem < 1 mm; glandular hairs on stem, leaves and abaxial calyx <= 0.1 mm, often only apparent as a resinous dot, much smaller than and often obscured by adjacent stellate hairs; stem surface and abaxial calyx lobe surface often hidden by dense hairs 3. Mature leaves adaxially sparsely stellate-hairy or occasionally stellate hairs 0, if more densely hairy, centers of stellate hairs average >= 0.5 {0.7} mm apart, branches of adjacent stellate hairs not overlapping throughout leaf Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets). surface; inflorescence generally with lobed bracts subtending highly reduced internodes Segment of an axis (generally a stem) between successive positions (nodes) from which one or more structures (especially leaves, buds, branches, or flowers) arise. , bracts ± as wide as long, widest bracts >=(5)7 {(6)8.5} mm wide measured below lobes 1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth. ..... M. involucratus (2) 3' Mature leaves adaxially densely stellate-hairy, centers of stellate hairs average <= 0.25 {0.35} mm apart, branches of adjacent stellate hairs generally overlapping throughout leaf surface; inflorescence with unlobed bracts subtending highly reduced internodes, bracts linear  Elongate, with nearly parallel sides; narrower than elliptic or oblong. to lanceolate  Narrowly elongate, widest in the basal half, often tapered to an acute tip. (rarely ovate), widest bracts <= 6.5(9) {8(11)} mm wide ..... M. palmeri 1' Inflorescence spike-like to panicle-like 4. Bractlets subtending calyx >= 1 {1.4} mm wide 5. Calyx lobes >= 1.2× wider above base than at base, ovate  Egg-shaped (i.e., widest below the middle) in two dimensions (i.e., in one plane), as a leaf. to widely so with sometimes abruptly acuminate  Having a long-tapered, sharp tip, the sides concave. tip; many stellate hairs on stem with stalks, a layer of those with stalked hairs covering those without stalks ..... M. aboriginum 5' Calyx lobes <= 1.2(1.4) × wider above base than at base, triangular to ovate; most stellate hairs on stem unstalked 4' Bractlets subtending calyx < 1 {1.4} mm wide 7. Stem glandular hairs <= 0.8 mm (mean per plant 0.1–0.5 mm); Vandenberg Space Force Base (western Santa Barbara Co.) ..... M. eastwoodiae 7' Stem glandular hairs <= 0.1 mm (mean per plant < 0.1 mm); Vandenberg Space Force Base and elsewhere 8. Mature leaves ashy- to bright-green adaxially, often paler abaxially, ± thinly yellowish to white stellate-hairy, more densely so abaxially; leaf base generally deeply cordate Heart-shaped; often pertaining to a leaf in which the blade base on both sides of the petiole is rounded and convex. , occasionally subcordate to truncate Abruptly (not gradually) narrower or smaller at base or tip, as if cut straight across or nearly so. 9. Bractlets subtending calyx 1.5–3 {2–3.5} mm; calyx stellate hair branches <= 0.5 mm (mean per plant 0.2–0.3 mm); plants generally 1–5 m; Monterey, n edge San Luis Obispo cos. ..... M. discombobulatus 9' Bractlets subtending calyx 2.5–8 {3–9.5} mm; calyx stellate hair branches <= 1.7 mm (mean per plant 0.3–1 mm); plants generally <= 2 m; Santa Barbara Co., eastern edge San Luis Obispo Co. ..... M. orbiculatus (G2, G6) 8' Mature leaves pale ashy- to light-green on both surfaces, often somewhat paler abaxially, densely white stellate-hairy on both surfaces; leaf bases generally subcordate to wedge-shaped (sometimes more deeply cordate in M. nuttallii) 10' Calyx stellate hair branches average <= 0.4 mm 11' Inflorescence generally panicle-like, if spike-like, population includes panicle-like inflorescences; flowering May and later 12. Bractlets subtending calyx and often flower buds 1. An incompletely developed, more or less embryonic shoot, usually covered with bud scales. 2. An unopened flower, often protected by sepals. reddish (buds when reddish due to red glandular hairs); leaves not lobed to obscurely 3-lobed ..... M. jonesii var. gracilis 12' Bractlets subtending calyx rarely and flower buds not reddish; leaves not lobed to clearly 3–7-lobed 13. Bractlets subtending calyx >= 3.5 {4} mm × >= 0.5 {0.7} mm wide; leaves unlobed to clearly lobed, surface wrinkled; Monterey Co., introduced along southern border San Luis Obispo Co. ..... M. abbottii (2) 13' Bractlets subtending calyx <= 3.5(5) {4(6)} mm × <= 0.5 {0.7} mm wide; leaves generally clearly lobed, surface smooth; Santa Barbara Co., southern edge San Luis Obispo Co., also widely planted ..... M. nuttallii (G4 G6)
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