Salix daphnoides, Violet willow
A slender and attractive tree, with reddish stems and furry white spring buds, having longstanding use of the bark and leaves to relieve back and joint pain.
scientific name Salix daphnoides Vill.
family Salicaceae
parts used Bark and leaves
Description
Violet willow is a large shrub or small tree growing to 6-8m in height and 2-3m wide. Supple branches carry leaves which are narrow and hairless. The leaf buds are characterised by a single scale. It flowers in early spring. The flowers are dioecious and only one sex is found on each tree. They are pollinated by bees and the seeds ripen in June. There is often variation in the species as well as hybridisation.
Habitat
Violet willow is native to central Europe, and widely naturalised elsewhere due to cultivation. It grows in wetlands and alongside rivers, doing well in sandy or pebbly areas.
Related plants
White willow (S. alba) is the traditional willow of herbal medicine and is fast growing to 25m. There are some 500 species in the Salix genus, and many are high in salicin content, the concentration measured in milligrams per gram dry weight as reported from the UK National Willow Collection at Rothamsted Research.1 Violet willow is recorded as providing 24.70mg/g salicin. Apart from white willow (S. alba) species containing between 8.4-12.21mg/g, another widely available species to consider is purple willow (S. purpurea) at 29.25mg/g. In North America, the black willow (S. nigra) is generally used.
Pollarded violet willow
Cultivation and harvest
Cultivation
Violet willow is hardy to USDA zone 5 (UK zone 5). It is fairly fast growing in sandy areas but does not tolerate competing plants well and needs weed-suppressing mulch. Suited to a wide range of soils, it prefers a sunny position and cannot grow in the shade. It prefers moist soil of neutral to acid pH. Willows have aggressive roots and should be planted well away from buildings and drains. Willow responds well to coppicing or pollarding in early spring. At Holt Wood, we mainly pollard and harvest the branches of violet willow after two or three years. The pollard branches of white willow are more vigorous in growth and are harvested every 1-2 years.
Pests and diseases
Willow is susceptible to honey fungus.
Propagation
Fresh seed has a very short viability, and is immediately surface sown. Cuttings of mature wood of pencil thickness can be taken in the dormant period, November to February, to be rooted in a sheltered outdoor bed or planted straight into their permanent positions. Cuttings of half-ripe wood are taken in June to August.
Harvesting
The bark of 2-3-year-old willow branches is harvested during the spring, when it readily peels off, and is dried for later use. Leaves can be harvested in late spring and used fresh or dried for later use. Drying recommendations vary; rapid drying in an airy room is best to reduce degradation of phenolic components. Twigs can also be harvested whole and cut into small pieces of 3-4mm.2
Therapeutic use
Traditional
Willow has been used since ancient times to treat pain and fever. The Assyrians used a decoction of willow leaves for joint pains, and Native American healers also relied on willow for its analgesic properties. Willow leaf tea was advised for painful childbirth in ancient Greece. Willow bark has been used to relieve sore throat, fever and headache associated with upper respiratory tract infections and influenza.
Medicinal actions and uses
Willow bark is antipyretic, analgesic, anti-inflammatory, antiseptic, astringent, tonic and bitter. The salicin content is hydrolysed in the intestinal mucosa to the aglycone saligenin which is then absorbed and oxidised in the blood and liver to give salicylic acid, which has an anti-inflammatory effect. Salicylic acid has little activity on platelet function in the blood unlike the manufactured aspirin acetylsalicylic acid.3 Willow bark is used mostly as an anti-inflammatory for symptomatic relief in back pain, joint pain, headache and toothache.4 An infusion of leaves can be used for calming in nervous insomnia, and in the bath for rheumatism.
Clinical applications and research
Despite a long history of use, relatively few studies have been published that confirm the effects of willow.5 The anti-inflammatory effects of a water-based extract of willow (23-26% salicin and high polyphenol content) have been confirmed, showing that the effects are not due to salicin alone, but due also to other polyphenols, flavonoids and proanthocyanidins.6 A small number of clinical studies have been conducted that support the use of willow bark extracts in chronic lower back and joint pain and osteoarthritis. For example, one study showed a moderate analgesic effect of 240mg salicin/day dosage given for two weeks in patients with osteoarthritis.7 A further review of research studies has provided moderate evidence of effectiveness for the use of ethanolic willow bark extract in lower back pain.8 Other uses have been considered for the antimicrobial leaves. A small-scale study compared a mouthwash of willow and mallow leaves with standard chlorhexidine in patients with gingivitis and found it comparable in terms of bleeding and plaque removal.9 Willow leaves have also been explored for their antimicrobial use in wound dressing applications.10
Sample preparations and dosage
Willow bark tea typically consists of 1-3g of bark per cup of water, decocted for 10 minutes, drunk three to four times per day. The infusion can also be used as a gargle for a sore throat. From 2-3 powdered willow bark capsules of 400mg can be taken 3-4 times daily, or willow tincture 5-8ml three times daily.
Constituents and commerce
Key constituents
Willow bark and leaves contain glycosides, salicylates (salicin, salicortin, populin, fragilin, tremulacin), tannins, aromatic aldehydes, and acids (salidroside, vanillin, syringin, salicylic acid, caffeic and ferulic acids), salicyl alcohol (saligenin) and flavonoids.11
Commerce
An alternative to willow was sought in the nineteenth century, partly because willow tended to upset the stomach when used. In 1899, the new compound acetylsalicylic acid was registered and introduced commercially as ‘aspirin’ by the Bayer Company of Germany. This new compound rapidly replaced willow as a medication. However, in Europe, the traditional use of willow bark extract is still accepted for lower back pain and for the symptomatic relief of fever associated with the common cold, minor articular pain and headache, at a standardised daily dosage equivalent to 240mg salicin. Willow products and raw materials are commonly imported from Eastern Europe and China. A quantity of 10g of willow bark has been reported to contain about 100mg total salicin. For comparison, commercial standardised bark extracts, with 120-240mg of the salicin constituent per day, are given for up to eight weeks for the treatment of pain.
Safety
Excessive use of willow bark in inflammatory joint disease means ingestion of high levels of tannin, which can irritate digestion, and so willow bark is best combined with other digestive herbs such as turmeric and ginger. Otherwise adverse effects appear to be minimal as compared to nonsteroidal anti-inflammatory drugs including aspirin. The primary cause for concern may relate to allergic reactions in salicylate-sensitive individuals.12 Due to the potential for Reye’s syndrome arising from salicylates, children with influenza, varicella or any suspected viral infection should avoid willow bark. Take professional clinical practitioner advice if on prescription medications. Not recommended in pregnancy or breastfeeding due to lack of sufficient data.
Other uses
Violet willow can be used to help stabilise sand dunes. Willows support many insects including moth caterpillars. Used in making medicinal charcoal. Hybrids are suitable for fast-growing biomass production in short rotation coppice.
1 Noleto-Dias C, Ward JL, Bellisai A, et al. (2018) Salicin-7-sulfate: A new salicinoid from willow and implications for herbal medicine. Fitoterapia 127: 166-172.
2 Upton R. (ed.) (1999) Willow Bark, Salix spp. Analytical, Quality Control and Therapeutic Monograph, Santa Cruz: America Herbal Pharmacopoeia, p6.
3 Bradley (1992) p224.
4 Committee on Herbal Medicinal Products (HMPC). (2017) European Union Herbal Monograph on Salix [Various Species Including S. purpurea L., S. daphnoides L., S. fragilis L.] Cortex, London: European Medicines Agency.
5 Shara M and Stohs SJ. (2015) Efficacy and safety of white willow bark (Salix alba) extracts. Phytother Res 29: 1112-1116.
6 Bonaterra GA, Heinrich EU, Kelber O WD, et al. (2010) Anti-inflammatory effects of the willow bark extract STW 33-I (Proaktiv(®)) in LPS-activated human monocytes and differentiated macrophages. Phytomedicine 17: 1106-1113.
7 Schmid B, Lüdtke R, Selbmann HK, et al. (2001) Efficacy and tolerability of a standardised willow bark extract in patients with arthritis: Randomized placebo-controlled, double blind clinical trial. Phytother Res 15: 344-350.
8 Vlachojannis J, Cameron M and Chrubasik S. (2009) A systematic review on the effectiveness of willow bark for musculoskeletal pain. Phytother Res 23: 897-900.
9 Radvar M, Moeintaghavi A, Tafaghodi M, et al. (2016) Clinical efficacy of an herbal mouth wash composed of Salix alba, Malva sylvestris and Althaea officinalis in chronic periodontitis patients. J Herb Med 6: 24-27.
10 Qureshi MA, Khatoon F, Rizvi MA, et al. (2015) Ethyl acetate Salix alba leaves extract-loaded chitosan-based hydrogel film for wound dressing applications. J Biomater Sci Polym Ed 26: 1452-1464.
11 Busia (2016) vol 2, p425.
12 Williamson et al. (2009), p399.