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Vascular Plants of California
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Amsonia tomentosa

Higher Taxonomy
Family: ApocynaceaeView DescriptionDichotomous Key
Habit: Annual, perennial herb, shrub, tree, often vine; sap generally milky. Leaf: simple, alternate, opposite, subwhorled to whorled, entire; stipules 0 or small, finger-like. Inflorescence: axillary or terminal, cyme, generally umbel- or raceme-like, or flowers 1--2. Flower: bisexual, radial; perianth parts, especially petals, overlapped, twisted to right or left, at least in bud; sepals generally 5, fused at base, often reflexed, persistent; petals generally 5, fused in basal +- 1/2; stamens generally 5, attached to corolla tube or throat, alternate lobes, free or fused to form filament column and anther head, filament column then generally with 5 free or fused, +- elaborate appendages abaxially, pollen +- free or removed in pairs of pollinia; nectaries 0 or near ovaries, then 2 or 5[10], or in stigmatic chambers; ovaries 2, superior or +- so, free [fused]; style tips, stigmas generally fused into massive pistil head. Fruit: 1--2 follicles, (capsule), [berry, drupe]. Seed: many, often with tuft of hairs at 1 or both ends.
Genera In Family: 200--450 genera, 3000--5000 species: all continents, especially tropics, subtropical South America, southern Africa; many ornamental (including Asclepias, Hoya, Nerium, Plumeria, Stapelia); cardiac glycosides, produced by some members formerly treated in Asclepiadaceae, used as arrow poisons, in medicine to control heart function, and by various insects for defense. Note: Asclepiadaceae ("asclepiads"), although monophyletic, included in Apocynaceae because otherwise the latter is paraphyletic. Complexity of floral structure, variation in asclepiads arguably greatest among all angiosperms. Pattern of carpel fusion (carpels free in ovule-bearing region, fused above), present +- throughout Apocynaceae (in broad sense), nearly unknown in other angiosperms. Base chromosome number generally 11; abundance of latex, generally small size of chromosomes evidently have impeded cytological investigations.
eFlora Treatment Author: Thomas J. Rosatti, except as noted
Scientific Editor: Bruce G. Baldwin.
Genus: AmsoniaView Description 

Habit: Perennial herb, erect, semi-woody. Leaf: alternate to subwhorled. Inflorescence: +- terminal, compound cyme. Flower: corolla salverform; filaments free, attached near top of corolla tube, unappendaged, anthers free from each other and stigma, pollen +- free; nectary 0 or a shallow ring around ovaries; style +- thread-like, stigma skirted at base. Seed: glabrous.
Species In Genus: 5--25 species: North America, Japan. Etymology: (John Amson, Virginia physician, 18th century)
eFlora Treatment Author: Thomas J. Rosatti & Lauramay T. Dempster
Unabridged Reference: McLaughlin 1982 Ann Missouri Bot Gard 69: 336--350
Amsonia tomentosa Torr. & Frém.
Habit: Plant glabrous or gray-tomentose. Stem: several to many from woody crown, 16--36 cm, branches few to many. Leaf: 2--4 cm; petiole short or 0; blade ovate-lanceolate, acute at both ends. Flower: calyx lobes erect, thread-like above base; corolla +- white, blue, or +- green, tube +- 15 mm, inflated above middle, narrowed just below spreading lobes; style with spheric thickening just below stigma. Fruit: 3--8 cm, constricted between seeds, often breaking into 1-seeded segments. Chromosomes: 2n=22.
Ecology: Desert plains, canyons; Elevation: 300--1800 m. Bioregional Distribution: SnBr (n slope), D; Distribution Outside California: to Utah. Flowering Time: Mar--May Note: Tomentose and glabrous plants (latter assignable to Amsonia brevifolia A. Gray) have identical ranges, do not intergrade, and show no other differences, suggesting hairiness is governed by a single gene.
Synonyms: Amsonia brevifolia A. Gray; Amsonia tomentosa Torr. & Frém. var. tomentosa
Jepson eFlora Author: Thomas J. Rosatti & Lauramay T. Dempster
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)

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Botanical illustration including Amsonia tomentosa

botanical illustration including Amsonia tomentosa


Citation for this treatment: Thomas J. Rosatti & Lauramay T. Dempster 2012, Amsonia tomentosa, in Jepson Flora Project (eds.) Jepson eFlora, /eflora/eflora_display.php?tid=13179, accessed on May 30, 2020.

Citation for the whole project: Jepson Flora Project (eds.) 2020, Jepson eFlora,, accessed on May 30, 2020.

Amsonia tomentosa
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© 2004 James M. Andre
Amsonia tomentosa
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© 2009 Keir Morse
Amsonia tomentosa
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© 2008 Steve Matson
Amsonia tomentosa
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© 2010 Neal Kramer
Amsonia tomentosa
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© 2008 Steve Matson
Amsonia tomentosa
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© 2006 Steve Matson

More photos of Amsonia tomentosa in CalPhotos

Geographic subdivisions for Amsonia tomentosa:
SnBr (n slope), D
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).


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Data provided by the participants of the  Consortium of California Herbaria.
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All markers link to CCH specimen records. The original determination is shown in the popup window.
Blue markers indicate specimens that map to one of the expected Jepson geographic subdivisions (see left map). Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time (fruiting time in some monocot genera).