Tree of the month: Willow

WillowleafNorthGower

This photograph of willow leaves, provided to the Centre for Biosciences Imagebank by Prof Paul F. Brain at the University of Wales, Swansea, illustrates an instalment in my Tree of the Month series.

I base this series (‘ogham’ tag) loosely on the ‘Ogham tree calendar’. That calendar was invented in the 19th century, directing attention to a different species for each lunar month but having little to do with ancient Celts’ Ogham alphabet. According to my casual interpretation of that calendar, I missed the Month of the Willow this year. But I’m admiring willow trees anyway because this huge genus (Salix spp.) is glorious. See the leaves! See the shapes! See what willows can do.

Willows can grow in many soils and in most climates. Most of them can regrow with vigour after being harshly cut. They can stabilise banks. They can be medicine, fodder, fuel, baskets and art. They support diverse ecosystems. They can clean water. I’ll write about just a few of those strengths and just a few of the willows. Because there are many kinds of willow.

Here are a few of the willows used for landscaping in Britain. The Online Atlas of the British and Irish Flora describes many Salix species found on these islands. Then there are the other plants whose common names include ‘willow’, the hybrids whose ancestry includes willow, and the willows which are native or naturalised in other parts of the world.

Here’s an example. Willows were introduced from Europe and Asia to the Americas. They’re now familiar there. This photograph of a weeping willow (Salix babylonica) in Boston, Massachusetts, USA was provided to the Centre for Biosciences Imagebank by Brian Wilson.

Bioscience Imagebank weeping willow copyright Brian Wilson

If you’re in the countryside of the British Isles, you’ll soon find wild or managed willows. The most common kind here is the goat willow (Salix caprea), also called pussy willow or common sallow. Here’s a map showing that S. caprea grows throughout Britain. Plants for a Future tells us more about the features and uses of S. caprea.

Most kinds of willow thrive near water. That is, they’re riparian. The Forestry Commission (FC) tells us that riparian woodland is valuable for its species richness and for its role in water management. Trees for Life agrees about riparian woods. These woods provide habitat for many species of vascular plants, fungi, mosses, lichens, invertebrates, fish, mammals and birds. That’s before you even start to admire the microorganisms. FC says that riparian woods can affect water quality, therefore needing the right kind of riparian habitat management.

I’ve not found clear science about why willows are riparian. Do please tell me if you know! My fellow blogger Rachel Bates at Ecology Escapades tentatively suggests that willows’ tendency to grow on riverbanks might be to do with the way their seeds germinate fast. Their cuttings or broken branches root fast, too.

Riverbanks are often disturbed by flooding. Then they can be colonised by pioneer plants such as willows. Whether arriving naturally, or being planted by land managers, this is when the willow shows its strength as a maker of land. A bit like marram grass (Ammophila arenaria) stabilising sand dunes on coastlines, willow stabilises riverbanks. Each of these pioneer plants has a root network which prevents the soil from being washed away. Then other plants can grow and an ecosystem develops.

Here are some more willow photographs, shown with permission from my fellow blogger Sophie at Naturanaute. On the left is a branch which I tentatively suggest might be S. babylonica. It’s hanging over the river Wey in Surrey, where it sheds seeds (on the right) at this time of year. If you’re a tree beside a river, you may as well use the water to disperse your seeds.

salix

Willows are often managed by coppicing or pollarding. These pruning methods cause the tree to grow many straight vertical stems, prolonging its life and producing wood for fuel or timber. To coppice, you cut the tree down to ground level. To pollard, you cut off all the tree’s branches some distance above the ground. You can read about coppicing and pollarding in a great landscape, the New Forest of Southern England, here.

Coppicing is useful when growing biofuels. That is, plant-based fuels. Here in Britain biofuels have attracted interest recently. The most promising plants for that purpose are willows and poplar (Populus spp.) grown as short rotation coppice (SRC). But is it a good idea to grow biofuels? Lewis Smith at the Daily Mail tells us that biofuels may not be a good choice for Europe. Harriet Jarlett at the Natural Environment Research Council says that there are pros and cons to British biofuel. Here’s some science about ecosystem processes in willow SRC plantations.

The biofuels story deserves a blog post of its own. So does sewage treatment, another way that willows can be useful plants. Here’s some science about using willow to treat sewage. I’ll try to get around to writing in more detail about biofuels and about sewage.

Meanwhile, here’s what the Royal Horticultural Society says about pollarding, traditionally done level with a man’s head or nearer the ground. Here’s a photograph of a willow soon after pollarding at waist height, provided to the Centre for Biosciences Imagebank by Prof Paul F. Brain at the University of Wales, Swansea.

CuttingWillowpollardedNWCW

My fellow bloggers the Wood Elves tell us about beautiful pollarded trees on French streets. I don’t know why pollarding isn’t routinely done in our British towns.

If pollarding hasn’t been done, or has been neglected, it can be used to tame huge willow trees. That’s when tree surgeons come in. Here’s a film in which a a team of tree surgeons pollard large willow trees. It looks quite fun, doesn’t it? Even without the speeded-up munchkin voices. But please, don’t try this at home unless you want to pollard yourself, which would be messy and perhaps fatal. If you’d like to learn how to pollard trees, you’ll need to be young, fit, and handy with a chainsaw. Here’s a directory of tree surgeons and arboriculture training in Britain. Here’s another film, showing how your working life could look. Or you could just watch from a safe distance.

If you did get an injury from a falling willow branch, you might choose to take a painkiller called aspirin. Which happens to be acetyl salicylic acid (ASA), derived from salicylic acid which in turn is derived from salicin. The clue’s in the name. Salicin is found in willow bark. Salicin from Salix. If aspirin suits you (but do check: aspirin’s not for everybody) you can buy a packet of aspirin tablets or you can chew willow bark as our ancestors did. The Traditional Roots Institute tells us that salicin is anti-inflammatory. ‘Like ASA, salicin has an anti-inflammatory effect in our body, making willow an excellent medicine for muscular and joint pains, fever pains, and gout.’

I’ll stop there but you get the picture. Willows are powerful plants and they’re beautiful plants.

About argylesock

I wrote a PhD about veterinary parasitology so that's the starting point for this blog. But I'm now branching out into other areas of biology and into popular science writing. I'll write here about science that happens in landscapes, particularly farmland, and about science involving interspecific interactions. Datasets and statistics get my attention. Exactly where this blog will lead? That's a journey that I'm on and I hope you'll come with me.
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2 Responses to Tree of the month: Willow

  1. Great blog post – willows are fantastic and versatile trees (as you have shown here) but get such a bad press because Hooman Beans put them in the wrong blinking places! We really need to get back to basics when it comes to arboriculture.

    • argylesock says:

      Glad you like it! Yes, I’ve seen terrible misplantings of trees which could have been great… if they’d been put in the right places.

      Talking of the right places, do you happen to know why willows are riparian?

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