White willow Salix alba, photographed by Willow.
Belongs within: Salicaceae.
Salix, the willows, is a genus of wind-pollinated trees and shrubs found mostly in arctic to temperate regions. Many species are grown as ornamentals and some have become widely invasive outside their native ranges. These include the weeping willow
S. babylonica, a native of northeastern Asia of which selected varieties are grown for their pendulous habit.
Characters (from
George W. Argus): Shrubs or trees, slightly heterophyllous, clonal or not, clones formed by root shoots, rhizomes, layering, or stem fragmentation; branching sympodial. Stems not spinose. Buds 1-scaled (rarely oily), margins connate into calyptra or distinct and overlapping adaxially, scale inner membranaceous layer usually not separating from outer layer, sometimes free and separating). Leaves deciduous or marcescent; stipules persistent, caducous, or absent (varying in presence and size on early and late leaves); petiole glandular-dotted or lobed distally; (blade often more than twice as long as wide, venation usually pinnate, margins entire, crenulate, crenate, serrate, serrulate, or spinulose-serrulate, teeth gland-tipped). Inflorescences axillary or subterminal, catkins, erect, spreading, or ± pendulous, sessile or terminating flowering branchlets, usually unbranched; floral bract apex entire, erose, bifid, or irregularly toothed; pistillate bract persistent or deciduous after flowering. Pedicels present or absent. Flowers: (sessile), perianth reduced to adaxial nectary (rarely also abaxial nectary, then distinct or connate into shallow cup); stamens 1, 2, or 3-10; filaments distinct or connate; ovary (stipitate or sessile), 2-carpellate; ovules (2-)4-24(-42) per ovary; styles usually connate, sometimes distinct distally; stigmas 2, entire or 2-lobed (less than 2 mm). Fruits capsular, (2-valved, obclavate to ovoid or ellipsoid). Seeds: aril present.
x = 19.
<==Salix [incl. Chosenia] T00
|--S. subg. Salix K07c
| | i. s.: S. babylonica Linnaeus 1753 K05 [incl. S. japonica LO98]
| |--S. sect. Salix K07c
| | |--S. alba Linnaeus 1753 K07c
| | | |--S. a. var. alba V09
| | | `--S. a. var. vitellina V09
| | |--S. fragilis Linnaeus 1753 K07c
| | | |--S. f. var. fragilis V09
| | | `--S. f. var. russelliana V09
| | `--S. × rubens Schrank 1789 K07c [S. fragilis × S. alba K07a]
| | |--S. r. nothvar. rubens V09
| | `--S. r. nothvar. basfordiana [S. alba var. vitellina × S. fragilis] V09
| |--S. (sect. Amygdalinae) triandra Linnaeus 1753 K05
| `--S. (sect. Pentandrae) pentandra Linnaeus 1753 K07c
|--S. subg. Chametia K07c
| |--S. (sect. Chamaetia) reticulata Linnaeus 1753 K07c
| | |--S. r. ssp. reticulata H93
| | `--S. r. ssp. nivalis H93
| |--S. sect. Glaucae K07c
| | |--S. glauca Linnaeus 1753 K07c
| | `--S. glaucosericea Floderus 1943 K07c
| |--S. (sect. Myrtilloides) myrtilloides Linnaeus 1753 K06
| `--S. (sect. Retusae) retusa Linnaeus 1763 K07c
`--S. subg. Vetrix K07c
| i. s.: S. helix [S. purpurea × S. viminalis] K07a
| S. × smithiana [S. cinerea × S. viminalis] V09
|--S. sect. Vetrix K07c
| |--S. appendiculata Villars 1789 K07c
| |--S. atrocinerea Brotero 1804 K05
| |--S. aurita Linnaeus 1753 K07c
| |--S. caprea Linnaeus 1753 K07c
| |--S. cinerea Linnaeus 1753 K07c
| | |--S. c. ssp. cinerea V09
| | `--S. c. ssp. oleifolia V09
| `--S. × reichardtii [S. caprea × S. cinerea] V09
|--S. sect. Arbuscella K07c
| |--S. foetida Schleich ex de Candolle 1805 K05
| |--S. phylicifolia Linnaeus 1753 K07c
| `--S. waldsteiniana Willdenow 1806 K05
|--S. sect. Daphnella K07c
| |--S. acutifolia Willdenow 1806 K07c
| `--S. daphnoides Villars 1789 K07c
|--S. (sect. Hastatae) hastata Linnaeus 1753 K07c
|--S. (sect. Helix) purpurea Linnaeus 1753 K07c
|--S. sect. Nigricantes K07c
| |--S. mielichhoferi Sauter 1849 K07c
| `--S. myrsinifolia Salisbury 1796 K07c
|--S. sect. Villosae K07c
| |--S. helvetica Villars 1789 K07c
| `--S. lapponum Linnaeus 1753 K07c
`--S. (sect. Vimen) viminalis Linnaeus 1753 K07c
Salix incertae sedis:
S. acuminata Miller 1768 K07b
S. amygdalina A81
S. amygdaloides B75
S. annularis C55b
S. arctica Pallas 1788 K07c [incl. S. anglorum var. antiplasta H93, S. anglorum var. petraea H93]
S. anticecrenata [incl. S. anticecrenata mstr. monadelpha] O88
S. bebbiana H93
S. bhutanensis O88
S. boothii [incl. S. pseudocordata] H93
S. brachycarpa H93
S. breweri H93
S. buergeriana LO98
S. caesia C55a
S. calyculata O88
S. capraea RCT96
S. caroliniana M83
S. cascadensis H93
S. daltoniana O88
S. delnortensis H93
S. discolor SF96
S. drummondiana [incl. S. drummondiana var. subcoerulea] H93
S. eastwoodiae H93
S. elaeagnos K06
S. eriocephala SF96
S. eriostachya O88
S. exigua (see below for synonymy) H93
S. geyeriana [incl. S. geyeriana var. argentea] H93
S. gooddingii [incl. S. gooddingii var. variabilis] H93
S. herbacea CS77
S. hookeriana [incl. S. piperi] H93
S. humboldtiana F11
S. hylematica O88
S. interior B75
S. jacquiniana C55a
S. jepsonii [incl. S. sitchensis var. angustifolia, S. sitchensis var. ralphiana] H93
S. karelinii O88
S. kirilowiana S00
S. laevigata [incl. S. laevigata var. araquipa] H93
S. lasiolepis (see below for synonymy) H93
S. laurina D37
S. lemmonii H93
S. ligulifolia H93
S. lindleyana O88
|--S. l. var. lindleyana O88
`--S. l. var. microphylla O88
S. lucida H93
|--S. l. ssp. lucida H93
|--S. l. ssp. caudata [incl. S. caudata var. bryantiana] H93
`--S. l. ssp. lasiandra [incl. S. lasiandra var. abramsii, S. lasiandra var. lancifolia] H93
S. lutea [incl. S. lutea var. watsonii] H93
S. melanopsis [incl. S. melanopsis var. watsonii] H93
S. myrsinites C55b
S. myrtillacea O88
S. nigra BV06
S. oreophila O88
S. orestera H93
S. ovatomicrophylla O88
S. pedicellata R-CT01
S. planifolia [incl. S. phylicifolia var. monica] H93
S. prolixa [incl. S. mackenzieana] H93
S. psilostigma O88
S. pycnostachya O88
S. repens Linnaeus 1753 K05
S. rosmarinifolia K06
S. sclerophylla O88
S. scouleriana [incl. S. scouleriana var. coetanea] H93
S. sericea SF96
S. sericocarpa O88
S. serpyllum O88
S. sessilifolia [incl. S. parksiana] H93
S. sikkimensis O88
S. silesiaca Willdenow 1806 K05
S. sitchensis [incl. S. coulteri] H93
S. sphenophylla Skvortsov 1966 K07c
S. subfragilis [incl. S. nipponica] LO98
S. tetraphylla P03
S. tetrasperma M72
S. varians Goeppert 1855 HL08
S. wallichiana SS72
Salix exigua [incl. S. hindsiana, S. hindsiana var. leucodendroides, S. hindsiana var. parishiana, S. exigua var. stenophylla] H93
Salix lasiolepis [incl. S. lasiolepis var. bigelovii, S. lasiolepis var. bracelinae, S. lutea var. nivaria, S. lasiolepis var. sandbergii, S. tracyi] H93
*Type species of generic name indicated
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Last updated: 1 January 2022.