Friday, 15 March 2013

Week 13: Sallow (Salix caprea and Salix cinerea)

Sallow was @SpeciesofUK from 24th February to 2nd March 2013.

Sallows are species of willow. Willows form the genus Salix. There's about 400 species of willow in total.

'Sallow' is the common name used for “Old World” (European) broad-leafed species of willow. In the UK, there are two species known as sallow, Great Sallow (Salix caprea) and Common Sallow (Salix cinerea), and these form the subject of this blogpost.

Great Sallow Catkins
[Source: juergen.mangelsdorf]

Great sallow and common sallow have various other names. Both are commonly known as ‘pussy willow.’

Great sallow can also be called ‘Goat Willow, ‘Sally’ or ‘Palm Willow.’ Common sallow is sometimes called ‘Grey Willow’ or ‘Grey Sallow.’ The word sallow is from Old English ‘sealh,’ which is related to the Latin name for the willow genus, ‘Salix.’[1]


Sallow can be found throughout the UK and is also native across Europe and western Asia. It’s fairly widespread and common.

Great Sallow in Spain
[Source: chemazgz]

It’s found in woodland, scrub and hedgerows, and particularly near water, e.g., canal sides or rivers, where it’s considered ecologically valuable for its use in stabilising banks and preventing soil erosion.[2]

Great Sallow and Common Sallow are often found side by side in hedges and hybridise easily.[3]


As with most other willow species, sallow is known for its thin watery bark sap, pliant tough wood, slender branches, catkins, and large fibrous roots.[4]

Great sallow and common sallow are very similar. Great sallow grows to about 12m and common sallow to about 10m. They sometimes grow as a tree or sometimes as a many stemmed shrub.[5]

Great Sallow Tree
[Source: Willow]

Great Sallow in Shrub Form
[Source: Willow]

(A tree, in case you're wondering, is a woody plant with a single large stem. A shrub is a woody plant with several stems and is smaller in height.)

Sallow bark grows fissured with age and is grey-brown. The twigs are hairy as first but with age (in great sallow) become smooth and (in common sallow) gain many raised ridges.[6]

The leaves are alternately arranged. Great sallow has large, oval leaves with a wavy margin. Common sallow leaves are narrower and taper at the base.[7]

Great Sallow Leaves
[Source: Willow]

Common Sallow Leaves
[Source: Rasbak]

Both great and common sallow leaves have downy white undersides and tips bent to one side, but common sallow’s narrow leaves often have rusty hairs too.[8]

The Catkins

Sallow is famous for its catkins. They start to appear at the end of February and are one of the UK’s harbingers of Spring.[9]

Catkins are flower "structures" with tiny/no petals and many individual flowers. They are found on a variety of UK trees including hazel, oak, birch, alder and sweet chestnut.

Sallow’s catkins appear before the leaves, making them prominent and easy to spot.[10] Sallow’s male and female catkins grow on separate trees.

The young male catkins are grey fluffy ovals.

Great Sallow Young Male Catkins
[Source: Bff]

These male catkins turn a brilliant gold as they become covered in flecks of bright yellow pollen.[11]

Great Sallow Male Catkins with Pollen
[Source: Krzysztof Ziarnek]

Common Sallow Male Catkin with Pollen
[Source: BCB]

Around the time that the male catkins gain pollen, the female catkins start to appear. These are stringy and green, and fertilised by wind or insect.[12]

Great Sallow Female Catkins
[Source: Willow]

Common Sallow Female Catkins
[Source: BCB]

By May, the female catkins become woolly with seeds.

Great Sallow Female Catkins with Seeds
[Source: Kenraiz]

As well as reproducing by pollination, sallows (like most willow species) can reproduce vegetatively. This happens when a branch touches the ground and takes root.[13]

Sallow and People

Sallow appears in Keats’s famous poem ‘To Autumn’: "Then in a wailful choir the small gnats mourn / Among the river sallows, borne aloft."[14]

Sallow timber is very soft and not many uses have been found for it apart from fuel. It’s too small for most uses and the twigs are too brittle for weaving.[15]

The travellers community, however, have traditionally used sallow to make clothes pegs and even used sallow rods to make their “bender tents.”[16]

A 'Bender' Tent
[Source: henna lion]

“Pussy Willow” twigs are traditionally broken off and used as “palms” in church processions on Palm Sunday because little else was in flower at that time of the year.[17]

Using Pussy Willow in Easter Parades has even spread to the USA
[Source: jamescastle]

Tradition has it that if a girl didn’t wear sallow in her hair on Palm Sunday, then she would get her hair pulled.[18]

Willow bark such as sallow has been known to alleviate pain since antiquity. The active ingredient, salicylic acid, proved to be basis of the development of aspirin.

Other Wildlife

Sallow supports a number of moths. These include the sallow kitten, sallow clearwing, dusky clearwing and more.[19]

Sallow Kitten Moth
[Source: ajmatthehiddenhouse]

Great Sallow is the primary food source for the purple emperor butterfly.[20]

Purple Emperor Butterfly
[Source: Maggi_94]

In early spring, sallow flowers provide an important food source for bees, insects, and nectar-feeding birds such as blue tits.[21]

Common Sallow Male Catkins with Bee
[Source: BCB]

Sawfly Larvae on Great Sallow
[Source: dnnya17]

Sallow can also be attacked by gall forming parasites such as the beetle aperda populnea.

Aperda populnea
[Source: Siga]

Strange but True…

Sallow male catkins are furry when they first appear and have been compared to kittens. This is where the expression “pussy” willow, the other name for sallow, comes from. Indeed, the word “catkin” itself is a loanword from Dutch “katteken” meaning "kitten."[22]

Immature Male Catkins, the origin of the name "Pussy Willow"
[Source: Phil Sellens]

[3] Derwent May, A Year in Nature Notes
[8] Derwent May, A Year in Nature Notes
[9] Derwent May, A Year in Nature Notes
[11] Derwent May, A Year in Nature Notes
[12] Derwent May, A Year in Nature Notes

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