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Tetradymia
axillaris |
Tetradymia
axillaris |
Tetradymia
axillaris |
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Tetradymia
axillaris |
Tetradymia
stenolepis |
Tetradymia
stenolepis |
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Tetradymia
canescens |
Tetradymia
glabrata |
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Trees and Shrubs of Kern County (Sep 2012) Tetradymia (horsebrush). Shrubs with alternate leaves in fascicles, spiny in two of the Kern Co. species, generally flowering in the spring and early summer except T. canescens flowering in the fall; flowers 4–9, yellow, all disk type, surrounded by 4–6 involucral bracts. Cypselae with numerous white capillary bristles. Bracts of old flower heads usually persist. Easily recognized by the small number of bracts in a single row, which may be mistaken for persistent sepals. All other genera of Asteraceae in Kern Co. have more bracts with exception to one species, Gutierrezia microcephala. 10 spp., western North America (FNA), 8 in California, 4 in Kern Co.; 3 used medicinally (Moerman), 12 extracts screened by the NCI before 1980, none active; 4 spp. collected for the NCI since 1996. 1. Plants spiny (leaves develop into spines)................................................................... 2 1. Not spiny....... ........... ............................................................................................. 3
2. Leaves as well as stems covered with white cottony hairs......... Tetradymia stenolepis 2. Leaves green, only the stems covered with white hairs................ Tetradymia axillaris
3. Leaves white hairy, flat, stems often hairy................................ Tetradymia canescens
3. Leaves green,
needle-like; stems covered with white cottony
Tetradymia axillaris Nelson 1904. var. longispina (M. E. Jones) Strother 1974 [Tetradymia spinosa Hooker & Arnott 1839 var. longispina M. E. Jones 1895]. Longspine horsebrush. Deciduous spiny shrub with rigid stems and branches, stems uniformly covered with cottony hairs; spines developing as modified leaves, slender, straight, 2–5 cm long; fascicled leaves needle-like, 2–12 mm; flowering Apr-May; flower heads mostly solitary on short stout hairy peduncles 4–15 mm in the axils of spines and fascicled leaves along the upper branches, bracts 5; flowers 5–7 per head; cypselae with felt-like hairs 9–16 mm. Joshua tree and pinyon-juniper woodlands, 4,000–7,000 ft. Southwestern Utah, southern Nevada, Sweetwater Mts., White Mts., Panamint Range, southern Sierra Nevada to San Bernardino Mts. Type from St. George, UT. Kern Co.” Occasional on the hot arid desert-facing slopes of the mountains west to Kelso Canyon and on the rocky slopes of on the north side of South Fork Valley west to Lake Isabella” (Twisselmann), 716–1,950 m (CCH). Tetradymia canescens DeCandolle 1838. Gray Horsebrush. Rounded deciduous shrub with numerous erect stems from a common basal area, to 80 cm; stems not uniformly covered with hairs, some parts lacking hairs, hairy parts in strips; without spines; instead, leaves in singles and fascicles, closely overlapping on upper parts of stems, narrow and flat, 8–10× longer than wide, 1–3 cm, spreading and recurved, sometimes mucronate, with short curly white hairs; flowering Jun-Sep; flower heads at ends of branches, 5–8 clustered in an umbrelliform arrangement, flowers usually 4 to a head, bracts 4; cypselae with or without silky hairs, the hairs shorter than pericarpium. Sagebrush plains and woodlands with Joshua tree, pinyon pine, junipers, and ponderosa pine below 10,000 ft; northern Rocky Mts. to New Mexico, west to southern California, north to British Columbia. Type from the Columbia River. Kern Co.: “Occasional in the pinyon woodland on the east slope of the mountains southwest to the Frazier Park region”; “grows as a matted subshrub among the granite outcrops and blocks on the southern Kern Plateau and around the high exposed metamorphic outcrops at Lookout Point in the Piute Mountains” (Twisselmann), 1,982–2,400 m (CCH). Tetradymia glabrata Torrey & A. Gray 1858. Littleleaf horsebrush. Rounded deciduous shrub with numerous erect stems and branches to 1.2 m; stems not uniformly covered with hairs, the hairy parts in strips; without spines; leaves mostly in fascicles, needle-like, 6–10 mm; flowering May–July; flowers heads at ends of branches, 5–8 clustered in an umbrelliform manner, flowers usually 4 in a head, bracts 4; cypselae with or without silky hairs, the hairs slightly exceeding the length of the pericarpium. Often on soils derived from limestone, or gypsum on sagebrush plains and slopes below 7,000 ft; mostly Great Basin Desert. Type from the Sierra Nevada. Kern Co.: “Scarce in the arid shrub and the creosote bush associations on the desert facing slopes of the mountains and in canyons in the western El Paso Range; rare on the sand dunes in the Muroc dry lakes region” (Twisselmann), 710–1,523 m (CCH). Tetradymia spinosa Hooker & Arnott 1839. Does not occur in Kern Co. It appears that CCH has records confused with the former synonym T. spinosa var. longispina. Tetradymia spinosa is found mainly in northeastern California, to Montana, Wyoming and New Mexico. Tetradymia stenolepis Greene. Mojave cottonthorn. Deciduous silvery spiny shrub with rigid stems and branches, stems uniformly covered with cottony hairs; spines developing as modified leaves, slender, straight, 2–3 cm long; fascicled leaves boat-shaped, 1–3 cm; flowering May–Aug; flower heads several to many crowded at ends of main branches, and also solitary heads at ends of upper shorter branchlets, bracts 5; flowers 5; cypselae with felt-like hairs 5–8 mm. Mostly Mojave Desert below 5,000 ft. Type collected between Cameron and Mohave, CA. Kern Co.: Rare in alkali sinks in the Boron and Muroc regions, west to Willow Springs and Mojave”, and northeast of Lake Isabella on metamorphic rocks (Twisselmann), but apparently more frequent further west, extending to Kelso Valley, Jawbone, and Tehachapi, 706–1,402 m (CCH). Spines used for treating warts (Moerman).
References on Pharmacological Activity in Tetradymia Jennings P.W., J. C. Hurley, S. K. Reeder, A. Holian, P. Lee, C. N. Caughlan and R. D. Larsen. 1976. Isolation and structure determination of the second toxic constituent from Tetradymia glabrata. J. Org. Chem. 41(26): 4078–4081.
Jennings P.
W., S. K. Reeder, J. C. Hurley, C. N. Caughlan and G. D. Smith. 1974.
Isolation and structure determination of one of the toxic constituents
from Tetradymia glabrata. Johnson. A. E. 1982. Toxicologic aspects of photosensitization in livestock. J. Natl. Cancer Inst. ;69(1): 253–258. “Two types of plant-caused photosensitizations are recognized in livestock: 1) primary, wherein the phototoxic agent in the plant is ingested and reaches the skin chemically unchanged; and 2) secondary, wherein the phototoxic agent in the porphyrin phylloerythrin produced by chlorophyll degradation in ruminant stomachs. Phylloerythrin is normally excreted in bile but is allowed to reach the skin when hepatic damage interferes with the phylloerythrin-excreting mechanism. Primary photosensitizing plant toxins are few, whereas secondary photosensitizations can be caused by damage to the liver by a variety of plant and other toxins. Plants causing each type of photosensitization are discussed and clinical manifestations of the disease in livestock are summarized. Tetradymia species are one of the most economically important causes of phototoxicity in livestock. The etiology of this phototoxic syndrome in sheep and the importance of sagebrush species as preconditioning agents for phototoxicity are discussed.”
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