Common Name: WILLOW FAMILY Habit: Shrub, tree; dioecious (monoecious). Stem: trunk < 40 m; wood soft; bark smooth, bitter; buds scaly. Leaf: simple, alternate, deciduous; stipules generally present, deciduous or not, often large. Inflorescence: catkin [or various, or flowers 1]; each flower subtended by 1 bract. Flower: perianth modified into non-nectariferous, cup- or saucer-shaped structure or reduced to adaxial nectary (rarely also with abaxial nectary, then free or fused into shallow cup). Staminate Flower: stamens 2--many. Pistillate Flower: pistil 1, ovary superior to 1/2-inferior, chambers generally 2--4, placentas parietal, stigma lobes 2--4. Fruit: berry, drupe, or 2--4-valved capsule. Seed: often with basal tuft of hairs. Genera In Family: 58 genera, 1210 species: widespread in tropics, northern temperate, arctic. Note: Now including many genera (e.g., Flacourtia, Idesia, Xylosma) formerly in Flacourtiaceae, at least in part because of presence on leaf margins in both families of salicoid teeth (vein extending to tooth tip). In California (and generally outside California), Populus pollinated by wind, Salix by insects, wind. Hybrids common; identification often difficult. eFlora Treatment Author: John O. Sawyer, Jr., except as noted Scientific Editor: Thomas J. Rosatti.
Common Name: COTTONWOOD Habit: Tree. Stem: < 40 m; young bark smooth, pale yellow-green to gray; older bark furrowed, brown to gray; twigs with swellings below leaf scars; winter bud generally resinous, scales > 3. Leaf: juvenile, adult, late-season leaves may differ in size, shape, hairiness; generally glabrous; blade 3--11 cm, elliptic to deltate, veins pinnate or +- palmate, tip generally elongate. Inflorescence: catkin pendent, 3--8 cm; bract cut into narrow segments; flowers sessile; nectary a cup- or saucer-like disk. Flower: perianth modified into non-nectariferous, cup- or saucer-shaped structure. Staminate Flower: stamens 8--60. Pistillate Flower: style short, stigmas 2--3(4), large, scalloped to 2-lobed. Fruit: spheric to conic; valves 2--3(4), 3--12 mm. Etymology: (Latin: name for plants of this genus) Reference: Hamzeh et al. 2006 J Torrey Bot Soc 133:519--527 Unabridged Reference: Hamzeh & Dayanandan 2004 Amer J Bot 91:1398--1408
Populus tremuloides Michx.
NATIVE Habit: Tree < 15 m; crown slender; highly clonal. Stem: twigs green-white, glabrous; winter buds shiny. Leaf: petiole 2/3 to = blade, laterally compressed; blade 2--4(7) cm, widely ovate to +- round, glabrous, adaxially green, abaxially glaucous, base rounded to cordate, tip tapered, margin finely crenate to serrate. Chromosomes: 2n=38. Ecology: Streamsides, moist openings, slopes in montane, subalpine forest, woodland, sagebrush steppe; Elevation: 900--3150 m. Bioregional Distribution: KR, NCoRH, CaR, SNH, SnBr, GB; Distribution Outside California: to Alaska, eastern North America, Mexico. Flowering Time: Apr--Jun Jepson eFlora Author: John O. Sawyer, Jr. Reference: Hamzeh et al. 2006 J Torrey Bot Soc 133:519--527 Index of California Plant Names (ICPN; linked via the Jepson Online Interchange) Previous taxon: Populus nigra Next taxon: Populus trichocarpa
Botanical illustration including Populus tremuloides
Citation for this treatment: John O. Sawyer, Jr. 2012, Populus tremuloides, in Jepson Flora Project (eds.) Jepson eFlora, https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=39509, accessed on January 25, 2025.
Citation for the whole project: Jepson Flora Project (eds.) 2025, Jepson eFlora, https://ucjeps.berkeley.edu/eflora/, accessed on January 25, 2025.
Geographic subdivisions for Populus tremuloides:
KR, NCoRH, CaR, SNH, SnBr, GB
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(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 occurrence).
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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).
