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Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Eudicots
Cladus: Core eudicots
Cladus: Asterids
Cladus: Campanulids
Ordo: Asterales

Familia: Asteraceae
Subfamilia: Asteroideae
Tribus: Astereae
Subtribus: Unassigned Astereae
Genus: Ionactis
Species: I. alpina – I. caelestis – I. elegans – I. linariifolius – I. stenomeres

Ionactis Greene, 1897

Greene, E.L. 1897. Pittonia 3(17C): 245–246.


Hassler, M. 2018. Ionactis. World Plants: Synonymic Checklists of the Vascular Plants of the World In: Roskovh, Y., Abucay, L., Orrell, T., Nicolson, D., Bailly, N., Kirk, P., Bourgoin, T., DeWalt, R.E., Decock, W., De Wever, A., Nieukerken, E. van, Zarucchi, J. & Penev, L., eds. 2018. Species 2000 & ITIS Catalogue of Life. Published on the internet. Accessed: 2018 Mar. 25. Reference page.
International Plant Names Index. 2018. Ionactis. Published online. Accessed: Mar. 25 2018.
The Plant List 2013. Ionactis in The Plant List Version 1.1. Published on the internet. Accessed: 2018 Mar. 25.
Tropicos.org 2018. Ionactis. Missouri Botanical Garden. Published on the internet. Accessed: 2018 Mar. 25.

Ionactis, common name stiff-leaved Asters or ankle-asters, is a small genus of plants belonging to the daisy family. These aster-like plants are endemic to North America (Canada and the United States).[3][4] One species is widespread across much of the eastern half of the continent, while two others are rare endemics with very restricted ranges (see below).[5][6]

The generic name, Ionactis, is derived from the Greek words "ion," meaning "violet" and "aktis" meaning "ray." This is in allusion to the ray florets, frequently pale purple in this genus.[7]

Ionactis was classified as a separate genus by Edward Lee Greene in 1897 with the species Ionactis linariifolia, which had been classified by Carl Linnaeus as Aster linariifolius. The species of Aster (in a strict sense) are now restricted to Eurasia.

The stiff-leaved Asters are perennial herbs with numerous green stems, about 2,5 cm long (rarely 10 cm), usually in a tussock. The spatulate leaves are small, stiff, sharply ascending and thick about the stem. The upper leaves are much smaller than the lower. Yellow-orange resin droplets form on the leaves of the Red Rock Canyon Aster (Ionactis caelestis).[7]

The involucral phyllaries (bracts under the flower head) are narrow and overlapping. They have, along the midrib, a narrow zone containing chlorophyll. The silky-hairy, fusiform achenes form a crown with a double pappus in two series, the inner one with long, barbellate bristles, the outer one with short bristles or minute scales.[7]

The small flower heads grow solitary or sometimes in a cluster at the end of the stems. The 10–24 fertile ray florets are nearly white, blue to pink, lavender, purple or blue violet. The sterile disc florets are yellowish. The peduncles are nearly naked.[7]

They have a chromosome base number of x = 9.[7][8]


Ionactis alpina (Nutt.) Greene - Lava ankle-aster - California Nevada Oregon Idaho Utah Wyoming Montana
Ionactis caelestis P.J.Leary & G.L.Nesom - Spring Mountain ankle-aster, aster - Red Rock Canyon National Conservation Area, Clark County in Nevada
Ionactis elegans (Soreng & Spellenb.) G.L.Nesom - Sierra Blanca Cliff Daisy. - Eagle Creek Canyon in Lincoln County in New Mexico
Ionactis linariifolia (L.) Greene - Flaxleaf Whitetop Aster, Grass-leaf Aster, Narrow-leaved White-topped Aster - eastern + central North America from eastern Texas to Québec and New Brunswick
Ionactis stenomeres (A.Gray) Greene - Rocky Mountain ankle-aster - British Columbia Washington Idaho Montana


1913 illustration from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 3: 444.
Flann, C (ed) 2009+ Global Compositae Checklist
Greene, Edward Lee. 1897. Pittonia 3(17C): 245–246 entirely in English
Tropicos, Ionactis Greene
Nesom, G. L. and T. J. Leary. 1992. A new species of Ionactis (Asteraceae: Astereae) and an overview of the genus. Brittonia 44: 247–252.
Nesom, G. 1994. - Review of the taxonomy of Aster sensu lato (Asteraceae: Astereae), emphasizing the new world species. Phytologia 77:141-297.
Flora of North America Vol. 20 Page 7,17, 82, Ankle-aster, Ionactis Greene
Xiang, C. & J.C. Semple. 1996. - Molecular systematic study of Aster sensu lato and related genera (Asteraceae: Astereae) based on chloroplast DNA restriction site analyses and mainly North American taxa. Pp. 393-423, in D.J.N. Hind & H.J. Beentje (eds.), Compositae: systematics. Proc. Intern.
The Plant List search for Ionactis
Biota of North America Program 2013 county distribution maps

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