Editing Willow (section)

==Description==
[[File:Salix silesiaca a5.jpg|thumb|At the base of the [[Petiole (botany)|petiole]] a pair of [[stipule]]s form. These may fall in spring, or last for much of the summer or even for more than one year ([[marcescence]]).]]

Willows all have abundant watery [[Bark (botany)|bark]] [[sap]], which is heavily charged with [[salicin]], soft, usually pliant, tough wood, slender branches, and large, fibrous, often [[stolon]]iferous [[root]]s. The roots are remarkable for their toughness, size, and tenacity to live, and roots readily sprout from aerial parts of the plant.<ref>{{Citation|last1=Dickmann|first1=D. I.|pages=8–91|publisher=[[Centre for Agriculture Bioscience International]] (CABI)|isbn=9781780641089|last2=Kuzovkina|first2=J.|doi=10.1079/9781780641089.0008|year=2014|chapter=Poplars and willows of the world, with emphasis on silviculturally important species|title=Poplars and willows: Trees for society and the environment}}</ref>

===Leaves===
The [[leaves]] are typically elongated, but they might also be round to oval, frequently with serrated edges. Most species are [[deciduous]]; semi-[[evergreen]] willows with [[coriaceous]] leaves are rare, e.g. ''[[Salix micans]]'' and ''[[Salix australior|S. australior]]'' in the eastern [[Mediterranean]].

All the [[bud]]s are lateral; no absolutely terminal bud is ever formed. The buds are covered by a single scale. Usually, the bud scale is fused into a cap-like shape, but in some species it wraps around and the edges overlap.<ref>{{cite journal |jstor=25027618 |title=The Genus ''Salix'' (Salicaceae) in the Southeastern United States |author=George W. Argus |journal=[[Systematic Botany Monographs]]|volume=9|pages=1–170 |year=1986 |issn=0737-8211 |publisher=[[American Society of Plant Taxonomists]]|doi=10.2307/25027618 }}</ref>

The leaves are simple, feather-veined, and typically linear-lanceolate. Usually they are serrate, rounded at base, acute or acuminate. The leaf [[petiole (botany)|petioles]] are short, the [[stipule]]s often very conspicuous, resembling tiny, round leaves, and sometimes remaining for half the summer. On some species, however, they are small, inconspicuous, and caducous (soon falling).

In color, the leaves show a great variety of greens, ranging from yellowish to bluish color.

Willows are among the earliest woody plants to leaf out in spring and the last to drop their leaves in autumn. In the northern hemisphere, leafout may occur as early as February depending on the climate and is stimulated by air temperature. If daytime highs reach {{convert|10|C|F|round=5}} for a few consecutive days, a willow will attempt to put out leaves and flowers.

In the northern hemisphere, leaf drop in autumn occurs when day length shortens to approximately ten hours and 25 minutes, which varies by latitude (as early as the first week of October for boreal species such as ''S. alaxensis'' and as late as the third week of December for willows growing in far southern areas).

===Flowers===
[[File:Young-catkin.jpg|thumb|Young male [[catkin]]]]
With the exception of ''[[Salix martiana]]'',<ref>{{cite journal|doi=10.1007/BF00986668|title=''Salix martiana'', a regularly hermaphrodite willow|year=1984|last1=Rohwer|first1=Jens|last2=Kubitzki|first2=Klaus|journal=[[Plant Systematics and Evolution]]|volume=144|issue=2|pages=99–101|bibcode=1984PSyEv.144...99R |s2cid=35590381}}</ref> willows are [[dioecious]], with male and female [[flower]]s appearing as [[catkin]]s on separate plants; the catkins are produced early in the spring, often before the leaves.

The [[staminate]] (male) flowers have neither [[Calyx (botany)|calyx]] nor [[Corolla (flower)|corolla]]; they consist simply of stamens, varying in number from two to 10, accompanied by a nectariferous gland and inserted on the base of a scale which is itself borne on the rachis of a drooping raceme called a catkin, or ament. This scale is square, entire, and very hairy. The anthers are rose-colored in the bud, but orange or purple after the flower opens; they are two-celled and the cells open latitudinally. The filaments are threadlike, usually pale brown, and often bald.

The [[pistillate]] (female) flowers are also without calyx or corolla, and consist of a single ovary accompanied by a small, flat nectar gland and inserted on the base of a scale which is likewise borne on the rachis of a catkin. The ovary is one-celled, the style two-lobed, and the ovules numerous.