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Hymenoxys brachyactis
(Tall bitterweed)

[taxon report][distribution map][all photos][line drawing]



Family: Asteraceae

Scientific Name: Hymenoxys brachyactis Wooton & Standley

Synonyms: None

Vernacular Name: Tall bitterweed

R-E-D Code: 1-1-3

Description: Biennial herb; stem solitary, branching above the middle, 3-6 dm tall, glabrous or sparsely pubescent in the inflorescence; basal rosette leaves dying when the plant flowers; stem leaves numerous, pinnatifid with narrowly linear lobes; inflorescence corymbose (flat-topped); involucre of flower heads 5-8 mm tall, outer phyllaries united for 1/3 to 1/2 their length, inner phyllaries ciliate-margined and blunt to acute at the apex; flowers yellow, ray corollas usually shorter than the length of the involucre; achenes appressed-hairy, pappus scales acute to acuminate at the apex. Flowers late July to September.

Similar Species: Hymenoxys richardsonii is a strong perennial with more than one stem. Hymenoxys vaseyi is usually perennial with one or more stems, has ray corollas as long or longer than the involucre, outer phyllaries united for 1/2 to 2/3 their length, and pappus scales blunt at the apex.


Distribution: New Mexico, northwestern Lincoln, northeastern Socorro, and western Torrance counties, southern Manzano Mountains, Gallinas Mountains, Los Pinos Mountains, and northern Chupadera Mesa.

Habitat: Dry sites with coarse soils in piņon-juniper woodland and lower montane coniferous forest; 2,100-2,500 m (6,900-8,200 ft).

Remarks: This New Mexico endemic was considered a synonym of Hymenoxys vaseyi for many decades. Now that additional field collections are available, the differences between the two taxa become more obvious and support the separation of these two species. The tall, single stem and monocarpic habit (flowers once - then dies) of H. brachyactis are especially diagnostic.

Conservation Considerations: This narrow endemic is locally abundant and will sometimes occupy disturbed sites. The prevailing land uses within its habitats do not threaten this species.

Important Literature (*Illustration):

Wooton, E.O. and P.C. Standley. 1913. Descriptions of new plants preliminary to a report upon the flora of New Mexico. Contributions from the U.S. National Herbarium 16:109-196.

Information Compiled By: Robert Sivinski, 1999

Agency Status:
Taxon USFWS State of NM USFS BLM Navajo Nation Natural Heritage NM Global Rank
Hymenoxys brachyactisSoCSoCSen..S3G3


Photo credits in header Peniocereus greggii var. greggii © T. Todsen,
Lepidospartum burgessii © M. Howard, Argemone pleiacantha ssp. pinnatisecta © R. Sivinski
©2005 New Mexico Rare Plant Technical Council