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RHAMNACEAE BUCKTHORN FAMILY

John O. Sawyer, Jr., except as noted

[Perennial herb] shrub, tree, generally erect, often thorny. Leaf: simple, generally alternate, often clustered on short-shoots; stipules generally present, occasionally modified into spines; generally petioled; blade pinnate-veined or 1–5-ribbed from base. Inflorescence: cyme, panicle, umbel, or flowers 1 or clustered in axils or on short-shoots. Flower: generally bisexual, radial; hypanthium subtending, surrounding, or partly fused to ovary; sepals 4–5; petals 0, 4–5, generally clawed; stamens 0, 4–5, alternate sepals, attached to hypanthium top, each generally fitting into a petal concavity; disk (0 or) between stamens, ovary, thin to fleshy, entire or lobed, free from ovary, adherent or fused to hypanthium; ovary superior or ± inferior, chambers [1]2–4, 1–2-ovuled, style 1, stigma entire or 2–3-lobed. Fruit: capsule, drupe.
50–52 genera, 950 species: especially tropics, subtropics some cultivated (Ceanothus; Frangula; Rhamnus; Ziziphus). [Richardson et al. 2000 Amer J Bot 87:1309–1324] —Scientific Editors: Steve Boyd, Thomas J. Rosatti.
Unabridged references: [Brizicky 1965 J Arnold Arbor 45:439–463; Richardson et al. 2000 Kew Bull 55:311–341]

Key to Rhamnaceae

ZIZIPHUS
Tree, shrub [vine]. Stem: branches alternate, flexible or stiff, ± 2–3-ranked; twigs ± pendent, zigzag. Leaf: clustered on short-shoots or not, deciduous or not, petioled; stipules ± spine-like or not, unequal; blade elliptic to obovate, ± entire to serrate, 1–5-ribbed from base. Inflorescence: cyme or small panicle. Flower: hypanthium surrounding base of ovary; sepals 5; petals 5, < to > sepals; stamens 5; disk thick, ± obscuring ovary in early flower; ovary widely attached at base, chambers 2, each 1-ovuled, stigma 2-lobed. Fruit: drupe, stone 1.
100 species: generally tropics. (Latin: from Arabic "zizouf," common jujube, Ziziphus zizyphus) [Islam & Simmons 2006 Syst Bot 31:826–842]
Unabridged references: [Johnston 1963 Amer J Bot 50:1020–1027]

Key to Ziziphus

Z. obtusifolia (Torr. & A. Gray) A. Gray var. canescens (A. Gray) M.C. Johnst. GRAYTHORN
NATIVE
Shrub, < 3 m. Stem: bark gray, smooth; twigs 1–8 cm, stiff, spreading, thorn-tipped, densely short-white-hairy. Leaf: deciduous; stipules brown; blade 2–20 mm, ovate or oblong, firm, dull gray, margin entire or teeth 2–10, glandular. Inflorescence: 2–30-flowered. Flower: hypanthium 1.5–2 mm wide, olive-green, glabrous to tomentose; sepals ± yellow to ± orange or ± purple; petals white; pistil olive-green. Fruit: fleshy, 7–10 mm, not beaked, blue-black.
Uncommon. Desert scrub; 45–1250 m. Desert; Arizona, Nevada, Utah, Mexico. 1 other var., in New Mexico, Oklahoma, Texas, Mexico. Apr–Jun [Online Interchange]
Unabridged synonyms: [Condalia lycioides var. canescens (A. Gray) Trel.]
Unabridged note: Ziziphus obtusifolia var. obtusifolia in New Mexico, Oklahoma, Texas, Mexico. Expanded author citation: Ziziphus obtusifolia (Hook. ex Torr. & A. Gray) A. Gray var. canescens (A. Gray) M.C. Johnst.

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Oct 1 2014
Citation for this treatment: [Author of taxon treatment] 2013. Ziziphus, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=67917, accessed on Oct 1 2014

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click for enlargement Ziziphus obtusifolia var. canescens
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2003 Debra Valov

Geographic subdivisions indicated for the distribution of Ziziphus obtusifolia var. canescens Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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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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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.