Willow, Salix: plant, prune and maintain

Description and Botany

The Willow is part of the Salicaceae family, just like the Poplar, and primarily inhabits the temperate to cold and rather humid regions of the northern hemisphere. Willow shrubs are pioneering species capable of forming a monospecific thicket in areas disturbed by cutting or fire, while tree willows like the goat willow often associate with other forest species.

The family, initially consisting of 2 or 3 genera, has expanded to include a significant portion of the Flacourtiaceae family, now counting a total of 55 genera, following the APG II phylogenetic classification (2003). Nearly 400 species are currently recorded in the Salix genus, with spontaneous hybridizations between these species being common – including polyploids, with up to 6 sets of chromosomes – and easily obtained artificially. The greatest diversity of Salix is found in China, followed by North America (100 species) and Europe (70 species). Identification often relies on flowering and fruiting.

The weeping willow is the most iconic representative of the genus, having been part of the European landscape for over two centuries. It is generally planted by bodies of water and in the lawns of large parks, although its longevity is quite low. Several species constitute the family of weeping willows, knowing that the original Chinese species Salix babylonica has given way to more robust hybrids like Salix x sepulcralis ‘Chrysocoma’, the most widespread, created in Berlin in 1888 and awarded the Award of Garden Merit by the Royal Horticultural Society in 1984. It is the result of an artificial hybridization between Salix alba ‘Vitellina’, hardy with yellow branches, and Salix babylonica ‘Babylon’, responsible for its weeping habit and which has also imparted its resistance to high temperatures, so it is not surprising to find Salix x sepulcralis ‘Chrysocoma’ even in tropical regions!

Salix caprea – botanical illustration

Willow leaves are deciduous, alternate, and simple, pointed at the tip. The lamina, 2 to 10 times longer than wide and borne on a short petiole, has entire or finely dentate edges. The foliage colour varies from the grey-green of goat willow to the bright green of weeping willows, passing through the golden tones of the cultivar Salix sachalinensis ‘Golden Sunshine’. The white willow (Salix alba) is recognized by the white and silky underside of the lamina. The base of the petiole is often accompanied by two stipules that are more or less persistent, leaving a V-shaped leaf scar after the leaf falls. The dimensions of the leaves, teeth, and stipules can sometimes be larger on the vigorous shoots of the plant. The buds are quite characteristic in willows as the terminal bud is absent due to the abortion of the tips of the branches, and the lateral buds covered by a single scale are applied against the branch.

The thin branches of the year display various colours: green (Salix viminalis), brown (Salix triandra), black (Salix daphnoides ‘Aglaia’), yellow (Salix alba subsp. vitellina), orange (Salix alba ‘Britzensis’), purple (Salix purpurea), or red (Salix fragilis) which basket makers appreciate. Willow producers prune every year between the first frosts of October and March the shoots of the year to encourage regrowth of over 1.50 m (wicker rods), resulting in the strange hairy silhouettes of pollarded willows typical of humid bocage areas.

The male and female flowering usually occurs on different subjects in the form of drooping or erect male catkins and erect female catkins. Some hybrids, like our famous weeping willow, are hermaphrodites. The male catkins have significant ornamental interest in certain species, well known in the cultivar Salix caprea Kilmarnork with its silky and ash-like appearance. New species and cultivars are sure to attract originality enthusiasts, such as Salix chaenomeloides Mount Aso with its 2.5 cm red-pink catkins or Salix hastata Wehrhahnii with numerous ovoid catkins that are initially silver and silky, elongating to measure up to 7 cm long, releasing many cream-yellow stamens. This flowering is well appreciated by bees that come to seek pollen and nectar sometimes as early as February, as with goat willow (Salix caprea). In weeping willows, flowering appears after leafing, so its ornamental interest remains quite limited. The greenish or yellowish flowers grouped in spikes have neither sepals nor petals but are preceded by a pubescent entire bract and accompanied by nectariferous glands. Pollination occurs both by wind and insects due to the characteristics of its thick and waxy pollen and its nectar. The willow constitutes a significant food source for pollinating insects, unlike the poplar, which is adapted solely for the wind dispersal of its naked pollen.

Salix caprea: difference between female catkins (left) and male catkins (right)

The fruits borne by female trees are 2-valved capsules that release green seeds bearing a white silky egret, dispersed by water or wind.

Although willow wood is not very durable, it is shock-resistant, lightweight, and homogeneous with a straight grain, making it suitable for making tool handles, boxes, or paper pulp, just like poplar. Their ability to sucker allows willows to stabilise banks.

The Latin name Salix designated the willow among the Romans.

The willow is laden with symbols, particularly in Tibet, where it evokes life, and in China, where it embodies immortality.

Willows exhibit a diversity of foliage: Salix alba, Salix integra ‘Hakuro Nishiki’ (Shrimp Willow), Salix sachalinensis ‘Golden Sunshine’, Salix lanata

The main varieties of Salix

Decorative Willows

Decorative Catkin Willows

Ornamental Foliage Willows

Salix alba Tristis - White Willow

The most popular and romantic of willows, Salix (x) sepulcralis 'Chrysocoma', also known as Salix alba 'Tristis', is a large tree with a broad rounded crown, featuring green foliage turning yellow in autumn and yellow trailing branches that reach the ground.

• Flowering time May, June
• Height at maturity 20 m

See the product sheet

Salix x erythroflexuosa - Willow

This small hybrid willow, reaching barely 4 m high and 2 m wide, offers both a twisted and weeping habit, showcasing beautiful elegance and rare originality. Its long spirally twisted branches, tinted with light orange-red to caramel, make a striking impression in winter and then in summer when they bear narrow, also curled and twisted leaves. Ideal by a water feature where it will make a statement.

• Flowering time April, May
• Height at maturity 4 m

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Salix matsudana Tortuosa - Dragon's Claw Willow

This medium-sized, fast-growing twisted willow raises its olive green twisted branches up to 10 m high. Its deciduous leaves, lanceolate and slightly dentate, are also twisted.

• Flowering time May, June
• Height at maturity 10 m

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Salix caprea Kilmarnock - Great Sallow

This small male goat willow grafted on a stem forms a regular parasol with trailing branches adorned at the end of winter with velvety grey catkins that turn yellow. Compact and very easy to grow in any slightly deep soil, even relatively dry in summer, it is perfectly suited for small gardens, as well as for container cultivation on the terrace.

• Flowering time March, April
• Height at maturity 3 m

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Salix gracilistyla Mount Aso - Black Willow

This Japanese willow offers remarkable fluffy pink-red catkins that are very decorative, blooming at the end of winter on its bare branches. Named Mount Aso in homage to the beauty of this volcano, almost as famous as Mount Fuji. Very cold-resistant, it will thrive in the sun, in cool soil.

• Flowering time March to May
• Height at maturity 3 m

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Salix gracilistyla - Black Willow

The Wolf's Claw Willow has an exceptional flowering from February to April, on its bare reddish branches, in the form of large black, silky catkins that release red anthers upon blooming. A small bush awarded by the prestigious Royal Horticultural Society, it will make a stunning impact in the garden.

• Flowering time April
• Height at maturity 2 m

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Salix subopposita - Willow

Dwarf willow with an adorable bonsai appearance in March-April when its small fluffy silver catkins unfold their golden stamens, literally covering its branches. The fluffy foliage is a very soft grey-green-blue. Well suited for small gardens and sunny rockeries, it thrives in ordinary, clayey, cool to moist soil.

• Flowering time April, May
• Height at maturity 1 m

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Salix integra Hakuro-Nishiki - Flamingo Willow

This small willow is certainly successful with its multicoloured and changing foliage, giving the illusion of flowering. Its fine foliage is variegated with pink and soft green in spring and turns white and medium green in summer. It grows easily in partial shade or dappled sunlight in any soil that is not too dry.

• Flowering time April, May
• Height at maturity 1,50 m

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Salix sachalinensis Golden Sunshine - Sachalin Willow

This rare shrub, of Japanese origin dating back only to 2007, has very bright fine foliage of a beautiful golden yellow. It is a reliable and healthy shrub whose rapid and vigorous growth allows it to reach its adult size (between 2.5 and 4 metres high) in no time. Plant it in rich, regularly amended soil, ideally cool to very moist, and prune it back in late winter.

• Flowering time April, May
• Height at maturity 4 m

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Salix magnifica - Willow

Behind its bushy silhouette with a rustic appearance lies a tree with precious hues that blend the marbled green of its large 20 cm leaves with the garnet of its young wood and petioles, not to mention the feathery red catkins that bloom in apple green.

• Flowering time April, May
• Height at maturity 7 m

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Young plantation

Where to Plant Willow?

In general, willows prefer a cool to moist soil, but they can also thrive in ordinary soil and will adapt to both light, stony, sandy soils and heavy, clayey, very wet soils. Most of them tolerate the presence of lime as well as sandy or slightly acidic soils and can withstand temporary flooding, while others can cope with dry conditions in summer with occasional generous watering, such as the coyote willow. Their tolerance to Siberian cold allows them to be planted in both plains and mountains, but they fear scorching summers.

Plant weeping willows, which are large trees, at a distance from buildings (at least 15 m) to prevent their roots from damaging pipes in search of water. Choose a non-paved location, a meadow, or the banks of a stream or pond.

A sunny or slightly shaded location is suitable for all willows.

Weeping willows can tolerate harsh winters (-40 °C) as well as tropical climates.

When to Plant?

Plant willows preferably in autumn to ensure deep rooting before facing summer drought.

How to Plant?

1. • Soak the root ball in a bucket of water to thoroughly moisten it.
   • Dig a planting hole 60 cm wide for large willows, 40 cm for shrub types, or a trench 50 cm wide for a hedge. Shrub willows can be spaced 1 to 2 m apart depending on their vigor and the extent you wish to give each bush. You can always plant a cutting in the ground to thicken the hedge!
   • Add a good amount of compost or potting soil to your garden soil if it is poor.
   • Place the plant in the planting hole after untangling any roots that may have circled in the pot.
   • Replace the soil and lightly compact it to form a basin.
   • Water.
   • Spread a layer of mulch at the base to maintain good moisture around the roots. This will also limit the growth of weeds. 

   The recovery is very easy and quick, requiring only monitoring of watering during the first 2 years after planting.

Pruning and maintenance of willow

Water regularly for the first two years, especially during hot and dry periods. This bush requires no other maintenance, except for pruning if necessary, which should be light and carried out after flowering.

Pruning Willows

Decorative willows for their aments (Salix caprea, alba …)

They benefit from being pruned every year or every 2-3 years to achieve long shoots bearing buds and to maintain a compact size. Take this opportunity to collect shoots with buds for floral decoration. Flower buds form on one-year-old wood, so pruning should not occur in winter, but just after flowering (except for the shoots intended for bouquets) to direct the sap towards a limited number of vegetative buds. The cut can be made at the same place, resulting in “pollarded” willows or “willow heads” with large swellings, or after the 1^st bud of the last shoot. Avoid damaging or removing the swellings, as they contain a significant portion of the tree’s reserves.

Ingrid explains in our tutorial: When and how to prune the shrimp willow?

How to prevent the leaves of the shrimp tree from drying out in summer?

Willows for basketry (Salix viminalis, triandra, purpurea, alba…)

• Prune at the same place every year the willow shoots after leaf fall and before the resumption of growth. The cut can be made at ground level to facilitate mechanical cutting or 50 cm or more above the ground to form the trunk of a pollarded tree.
• Form homogeneous bundles and keep the living shoots by soaking their bases in 10 cm of water. If the shoots are not kept alive, their bark will turn brown and wilt after 3-4 years. This is why the shoots are sometimes treated in an autoclave to prolong their outdoor viability.
• Fully submerge the shoots in water for 8 to 10 days before weaving to soften them. The weaving of living shoots should be done between December and April.

Basket willows

White willow is dry and only needs a few hours of soaking to soften: the shoots kept alive until the resumption of growth in May have been stripped of their bark, giving them this light colour.

To learn more about basketry

Weeping and twisted willows (Salix chrysocoma, sepulcralis, babylonica)

Pruning is important at the start to ensure the trunk gains sufficient height before allowing its branches to droop. A plant left to its own devices will form a tree twice as wide as it is tall.

Be aware that willows do not tolerate large diameter cuts (over 5 cm) well, as they heal poorly, leading to heart rot. The light wood is then less able to support weight and breaks easily, which is why tree formation should begin at a young age. Apply the following pruning technique to gradually raise the crown:

• When the trunk exceeds about 2.20 m, select the 5 or 6 branches that will serve as the starting point for the crown.
• At the end of winter, prune them just above a bud located at the top of the curve (30-40 cm from its base).
• Remove the others at the trunk level.
• Repeat the same operation on the new shoots in subsequent years to raise the crown in overlapping arcs.
• In parallel, remember to remove all weak branches, those that cross, and those with cankers (disinfect the pruning shear between each cut).

[caption id="attachment_53096" align="alignnone" width="1172"] Twisted willow

Potential Diseases and Pests

Willows are generally quite robust if they do not suffer from stress due to lack of water or severe pruning.

The foliage is sometimes subject to anthracnose, which causes black spots surrounded by yellow on the leaves and shoots in spring and summer. Leaves fall, and cankers form, preventing sap flow. Scab leads to black spots on the underside of leaves and then on young leaves, causing shoots to bend and dry out, covered in black lesions. Black canker also causes leaf spots and cankers.

In all three cases, collect and burn fallen leaves on the ground and quickly prune diseased shoots. Spray a fungicide once a month from March if the attack recurs.

caterpillars and aphids followed by sooty mould deposits can affect young plants and may require insecticidal treatment (pyrethrin…). Most of the time, no intervention is needed.

→ Learn more about willow diseases and pests

Multiplication: propagation by cuttings

Propagation by cuttings

It is the simplest and most effective way to multiply willows. Cut branches of any size and plant them in loosened soil, then water. Rooting is very quick, making the formation of a hedge of small willows very easy to achieve!

→ Learn more about the propagation by cuttings of willow in our tutorial!

Uses and associations

There is such a diversity of shapes, sizes, and cultural requirements among willows that it is impossible not to find a specimen that will thrive in your garden. A willow always brings a bucolic and natural touch, sometimes very original, romantic, or even elegant, depending on the varieties.

Weeping or twisted willows benefit from being planted in isolation in the middle of a short grass meadow or on the banks of a pond colonised by water lilies or lotuses, or by a river. The silhouette of these trees inspired many poets and romantic writers such as Alfred de Musset, as well as painters like Monet, who see in this shape a kind of melancholic evocation. Their dimensions can be extremely variable (7 to 20 m) depending on the cultivar and water availability. Be sure to gather information from your nurseryman before planting a willow, as it can be difficult to remove if it becomes troublesome. The lifespan of a weeping willow can reach around a hundred years. It can form a beautiful ensemble on the banks of a pond or lake alongside Bald Cypress, Liquidambars, Tulip Trees, Nyssa sylvatica, and Gunnera, which require the same moist conditions.

Majestic weeping willow on the edge of a pond

The white willow (Salix alba), capable of reaching 25 m in height, makes an excellent windbreak, shimmering with its silver-backed foliage. It has given rise to several cultivars with coloured wood used in basketry, such as Britzensis and Vitellina, which can be trained as low pollarded trees.

Small and medium willows ranging from 1 to 7 m in height, decorative for their coloured bark, foliage, or aments in spring, can form rustic hedges that can be cut back as desired. They are also delightful in a mass planting alongside a Beech, Hazel, Witch Hazel, and a Physocarpus with purple or golden foliage. To add a touch of lightness to the scene and enhance it with warm tones in summer and autumn, plant clumps of Miscanthus or Panicum in the foreground. By a large body of water, plant them alongside dogwoods with coloured bark (Cornus sanguinea, Cornus sericea), Miscanthus, Gorse, or Bulrushes. Create a floral tableau in a bohemian chic style in white and gold, with a backdrop of an ornamental apple Malus Golden Hornet, then Salix sachalinensis Golden Sunshine, an Itea virginica Henry’s Garnett or Little Henry’s, and in the foreground, a few clumps of Ligularias.

An idea for a white and gold association: Malus ‘Golden Hornet’ (©Horticolor Lyon), Itea virginica ‘Little Henry’s’, Salix sachalinensis ‘Golden Sunshine’ and Ligularia dentata ‘Britt-Marie Crawford’

To create a rainbow hedge, simply introduce different willows with coloured foliage such as the shrimp willow for pink and cream, Salix rosmarinifolia for silver-grey, Salix sachalinensis Golden Sunshine for gold, not forgetting the magnificent willow (Salix magnifica) for its jade tones…

In a rockery with deep clay soil, install the dwarf Japanese willow, Salix subopposita, with bonsai-like features. This compact shrub, with slow growth, reaching 1 m in height and 1.20 m in width, is covered with silver aments, then golden in March-April, before the appearance of the soft, grey-blue-green, downy foliage. It also forms lovely ground-cover borders, adorns a bank, and fits easily into a large pot on the terrace where one can enjoy its remarkable flowering up close, followed by its beautiful foliage. To enliven a low-maintenance hedge or mass planting, pair it with dwarf Forsythia, dwarf purple Barberry, Russian dwarf almond (Prunus tenella), or even the dwarf ornamental apple Malus Pom Zai.

Remarkable small specimens like Mount Aso willow can be placed as a focal point in the middle of a mass of early bulbs consisting of snowdrops, crocuses, fritillaries, and hyacinths. It also forms a lovely shrub mass in pink tones with Prunus triloba, flowering cherries, and plums.

An example of a spring association: Salix chaenomeloides ‘Mount Aso’, Fritillaria meleagris, Crocus, Galanthus nivalis, and Helleborus orientalis

→ Discover more ideas for pairing with willows in our advice sheet!