Willow Trees and Shrubs: Interesting Plants With Useful Features
Willows are attractive and interesting plants that have many uses. The plants belong to the genus Salix and exist as trees or shrubs. They are famous for their salicin content. The study of this chemical's structure led to the creation of acetylsalicyclic acid (also known as ASA and aspirin). Another potentially useful chemical named miyabeacin has recently been discovered in the genus. The chemical might help to fight some types of cancer, though it has only been tested in cell cultures at the moment.
Willows grow well where I live and are one of my favourite plants. I’m always pleased to see their catkins appear in spring. In this article, I discuss the following topics related to the plants.
- The willow family
- Selected willow species
- The Salley Gardens song
- Uses of willows
The Willow Family
Willows belong to the plant group known as Angiosperms (flowering plants) and the family Salicaceae. Poplar trees, cottonwoods, and aspens also belong to this family. The members of the family are valued by many people. Their flowers are arranged in catkins and are often an attractive sight in early spring.
Wild willows are found mainly in the northern hemisphere and in areas with a temperate climate and moist soil. Some species live in cold regions such as arctic and alpine environments, however, where they may reach just a few inches above the ground and have an atypical appearance. Willows are popular as cultivated plants and are planted in some areas where they don't grow naturally.
The Salix genus contains several hundred species. The stated number ranges from three hundred to a little over four hundred, depending on the source. Naturally-created hybrids and ones created by horticulturists produce an even larger number of willow types. They are interesting to explore.
The white willow (Salix alba) is a medium to large tree. It's known for the almost white undersurface of its leaves and the paler than normal upper surface. It's native to Europe and Asia.
Features of the Leaves
Willows are deciduous. Most have leaves that are long and narrow with an even narrower base and a pointed tip, as shown in the photo above. Some species have wider and oval leaves, including the great sallow or goat willow. I discuss this plant later.
The margin of the leaves is toothed in some species but not in others. The leaves are smooth or pubescent (hairy). They are usually attached to the stem in an alternate arrangement, but there are some exceptions to this rule.
Though the upper surface of the leaves is generally a shade of green, the colour varies slightly. Some plants have yellow-green, red-brown and green, or grey-green leaves, depending on the species, the stage of development, or the time of year. An impressive cultivated plant known as Salix integra 'Hakuro Nishiki' has variegated leaves that are a mixture of white and pink. This plant is shown in the last photo in the sequence above.
The Del Norte willow is a shrub that is native to southern Oregon and Northern California. It grows in mountainous habitats and forms thickets. The stamens in the catkins are purple or red at first and then become yellow.
Willows reproduce by means of catkins, which appear before the young leaves unfurl. A catkin is a thin spike of flowers. Willows are dioecious, which means that all of the catkins on a plant bear only female flowers or only male ones. The petals of the flowers are small or absent. The flowers may contain a small bract, however. They have no scent. Despite these facts, they are often attractive.
"Pussy willow" is a term used for various species that produce catkins with a hairy, furry, or woolly appearance. The very noticeable and attractive catkins remind people of a cat's tail, which is probably why the plant was given its nickname. The "fur" protects the young catkins. As the catkin matures and expands, the flowers and their reproductive structures become visible.
The male flowers contain the stamens that produce pollen. The female flowers contain a pistil, which in turn contains a stigma to catch the pollen, an ovary, and the ovules located inside the ovary. Each ovule contains an egg cell. Like other flowering plants, willows reproduce sexually. Pollination is performed by wind and insects. The fruit that develops from an ovary is a capsule that breaks open to distribute the seeds.
The Great Sallow or Goat Willow
Salix caprea is known as the great sallow. It's also called the goat willow and the pussy willow. According to The Wildlife Trusts (a registered UK charity for protecting nature), the plant is also known as a sally. It's native to Europe and Asia. It has oval leaves instead of narrow ones and grows as a small tree.
The male catkins are very attractive and are responsible for the pussy willow name. They are one to two inches long, grey in colour, and have a furry or woolly appearance. The female catkins are less attractive and are smaller. They have pale green pistils with flask-shaped ovaries and aren't furry at first. This changes when the seeds appear. The mature seeds bear long and silky hairs. The fruit opens up to release the seeds, which are distributed to a new habitat by the wind.
Like sallows, osiers are willows. Salix viminalis is known as the basket willow or the common osier. It has the typical narrow and elongated leaves of a willow. Historically and in the present, the narrowest branches of the plant have been used to make baskets.
Salix × sepulcralis 'Chrysocoma' is known as the weeping golden willow. It's an artificial cross between a particular variety of Salix babylonica and Salix alba. It's a frost hardy plant. The photo above was taken in December.
The Beautiful Weeping Willow
The lovely weeping willow tree is Salix babylonica. It's a large tree whose branches form a graceful arch. In scientific terms, they are said to be pendulous, or hanging. The plant has been a favourite tree of mine since my childhood. The one in my photo above was taken by Lost Lagoon in Vancouver's Stanley Park.
S. babylonica is native to East Asia but has been planted in many other places. The tree likes moist soil and bright sunlight. I usually see it beside a lake or a pond. The land beside Lost Lagoon is a suitable habitat for the plant because the lagoon contains fresh water. The catkins of the tree aren't particularly showy. The tree is valued for the lovely appearance created by the drooping branches and its mature leaves.
The Dwarf or Snowbed Willow
The dwarf or snowbed willow (Salix herbacea) is an unusual but attractive member of its genus. It's important to look at the scientific name of a plant when exploring its features. There is at least one other species of Salix known as the dwarf willow. Snowbed willow is an appropriate name for the plant because it grows where snow is found during at least part of the year. The plant lives in the Arctic at ground level and in the alpine environment at the top of high mountains. It has a wide distribution and is found in multiple countries.
The dwarf willow is very small. It ranges from 0.5 cm to 5 cm in height. Each plant produces only two or three leaves, which are rounded or elliptical in shape. The leaves are crenulated, which means they have a wavy margin, and they curl upwards. Like other willows, the plant produces male and female catkins. The female catkins produce a red capsule as a fruit.
Salix purpurea is known as the purple willow or the purple osier. The young catkins are often purple or red, which is an unusual colour. The young stems sometimes have a purple or red tinge as well. The colour fades as the plant matures.
The Salley (or Sally) Gardens Song
Listening to "The Salley Gardens" song was part of my childhood. The word "salley" is believed to be related to the word "sallow". In the past, villages sometimes maintained a willow plantation nearby to provide thatch for the roofs of cottages. The garden had another function. It was a spot where couples met.
The song was based on a poem by William Butler Yeats, an Irish writer. His poem was in turn based on three lines of a song that he had heard a local woman sing in the past but couldn't fully remember. The song has three verses. The lyrics of the first one are shown below. The third verse is the same as the first one, except the word "love" replaces "life" in the fifth line.
Down by the salley gardens
My love and I did meet
She passed the salley gardens
With little snow white feet
She bid me take life easy
As the leaves grow on the tree
But I being young and foolish
With her did not agree
Maura O'Connell is the main singer in the video above. She was born in Ireland. She's known for blending folk songs with country music.
History of Salicin and Aspirin
Aspirin is an impressive medication that has many potential benefits in the body and whose history is linked to willow plants. The International Aspirin Foundation was set up to study the chemical's effects. The foundation has multiple medical and scientific advisors.
Salicin and Salicylic Acid
According to the Aspirin Foundation, even as early as 400 BC, Hippocrates was giving women willow bark to help relieve the pain created by childbirth. The inner bark of a willow contains the highest concentration of salicin. The substance is converted to a compound called salicylic acid in our body. The acid can also be produced in a laboratory. Unfortunately, it can irritate the gut.
Production of Acetylsalicylic Acid
Felix Hoffmann from the Bayer company found a way to turn salicylic acid into acetylsalicylic acid. This was found to be a less irritating substance than salicylic acid. Today the chemical is known as ASA or as aspirin. Hoffmann's last name is spelled with both one n and two. I've used two as the Bayer website does.
Aspirin can be very useful but can also cause potentially harmful side effects. If the medication is used more than occasionally, a doctor's advice should be sought. Parents should also seek a doctor's advice with respect to giving children and teenagers aspirin. The drug is linked to an increased risk of a serious condition called Reye's syndrome in this age group.
Possibly because of the success of aspirin, medicinal assessment of other salicinoids in willow has been mostly neglected by modern science, and the National Willow Collection has proven to be a gold-mine of exciting new chemistry.— Dr. Jane Ward, Rothamsted Research
Rothamsted Research and Miyabeacin
Rothamsted Research is a renowned agricultural research institute in Britain. It originated in the nineteenth century. My father was a soil scientist and was associated with the institute, which at that time was known as the Rothamsted Experimental Station. While I was doing research for this article, I found an Amazon UK page listing a publication written by my father and published by the station. The discovery was a lovely link to the past.
Today, Rothamsted Research has a very large collection of willow plants and tissues known as the National Willow Collection. In combination with biologists from the University of Kent, researchers at the institute have made an interesting discovery. They've found a previously unknown chemical called miyabeacin in willow tissues. They've also found that this chemical kills cancer cells in the lab, including those of a type that is resistant to other drugs.
It's important to note that the scientists haven't yet tested the chemical in animals or in humans. Results in lab equipment are not always the same as results inside living bodies. Nevertheless, the discovery of miyabeacin could be significant.
The National Willow Collection began in 1923 after the first world war caused a serious problem in Britain's basket willow population.
Miyabeacin Structure and Laboratory Effects
The researchers have discovered that a miyabeacin molecule has two salicin groups, which they say enables it to give a "double dose of anti-inflammatory and anti-blood clotting ability."
In laboratory experiments with cell cultures, miyabeacin was active against cells of several cancer types, including throat, ovarian, and neuroblastoma ones. Neutoblastoma generally affects children and is sometimes challenging to treat.
Even if miyabeacin is not found to be helpful in living organisms, it's possible that scientists could modify the structure of the molecule in some way to enable it to work. The quote from Dr. Jane Ward shown above offers hope that willow plants may contain other useful chemicals for us. Nature can be valuable in more ways than one.
Uses of Willows
Willows have other uses besides being a source of salicin and miyabeacin. The branches of certain species are still used for making baskets as they were in the past and are also used in other forms of wickerwork. The wood of willow trees is used by artisans to make rustic furniture. One variety of Salix alba is grown in the UK to provide wood for cricket bats.
Willow bark contains chemicals called tannins as well as salicin. Historically, the tannins from certain willows were used to turn animal hides into leather. The bark is sometimes used to make string.
The intact plant is also useful. It's grown for use as a biofuel. A biofuel is derived from biomass, such as the bodies of plants or algae or the waste created by animals. It's considered to be a renewable energy source.
Specific species of willows are planted as shelterbelt trees and shrubs. A shelterbelt is a barrier made of living plants that protects a sensitive area from adverse environmental conditions, such as wind or storms. Willows can help to prevent the erosion of land.
Lovely Plants With Possible Drawbacks
I admire wild willows near my home and planted willows in parks, but I've never grown the genus in my garden. Some species are said to be invasive. The roots of certain willows can spread aggressively. They may damage items such as underground pipes and may even crack sidewalks. The location where a cultivated willow is planted, its potential size when mature, and its possible effects should be considered carefully.
I'm content to observe willows in the wild and in parks, which I always enjoy. They are interesting to see and to investigate. The chemicals inside them may have more benefits than we currently realize. That's a lovely thought.
- Willows in North America from Native Plants PNW (Pacific Northwest region of North America)
- The Willow entry from the Canadian Encyclopedia
- Facts about pussy willows from the Brooklyn Botanic Garden
- Great sallow facts from the Missouri Botanical Garden
- Information about the goat willow from The Wildlife Trusts
- Weeping willow facts from the North Carolina State University
- Information about the dwarf or snowbed willow from the New York Natural Heritage Program
- "Down by the Salley Gardens" information from Irish Music Daily
- Aspirin timeline from the International Aspirin Foundation
- Willow bark information from WebMD
- A willow chemical that may be an anti-cancer compound from the Medical Xpress news service
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
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© 2020 Linda Crampton