Wednesday, February 03, 2021

The down on the birch


Winter shoots of Silver Birch (Betula pendula, left) and Downy Birch (Betula pubescens, right)

Our two native birch trees are Silver Birch (Betula pendula) and Downy or White Birch (Betula pubescens). (There's also the Dwarf Birch of mountains -- Betula nana -- but that's only about six inches tall.)

Silver Birch is the prettier tree, but Downy Birch does often crop up in town gardens (and I always wonder if it was an accident, or perhaps arose as a natural seedling). Anyway I walked past both species yesterday and grabbed a couple of winter shoots to look at more closely. (Partly because I've just been writing about them in connection with Scott's Waverley.)

Well, obviously Downy Birch has downy twigs, and Silver Birch doesn't. (Actually it sometimes does, on very young growth, but let's not worry here about the complications, there are BSBI papers for field botanists who need to pin down every single individual birch in their area.)

Even a casual glance shows that the Silver Birch twig is shinier, and the Downy Birch twig is more matte.

Silver Birch (Betula pendula)

Downy Birch (Betula pubescens)

Silver Birch (Betula pendula)

Downy Birch (Betula pubescens)

Both twigs have small white resin-spots, but they're much more noticeable on Silver Birch, because of its lack of downiness.

I wanted to see the actual down. It needs a good lens because the hairs are very small indeed. You can see them (just) on the edge of the twig near the leaf bud in the ultra-closeup below.

The down on Downy Birch (Betula pubescens)

Downy birch is one of few broadleaved deciduous trees in the Arctic and it is hardier even than most conifers. Its “down” is a soft coating of hairs that acts like a fur coat in the punishing cold. Often found cooperating with pines and spruce at lower latitudes and altitudes, above a certain point the birch leaves the others behind and goes on alone for hundreds of miles.

Considering how minute the down is, there might be some exaggeration in Ben Rawlence's description of it as a "fur coat" (as if trees were warm-blooded and the down is the main reason why Downy Birch grows further north than any other tree).

Nevertheless, it's a fact that Downy Birch is the pioneer forest-forming species in the arctic. The article describes its alarming spread across the warming tundra and how it threatens the reindeer-herding culture of the Sami in Finnmark. 


This isn't the place for a full disquisition or celebration of birch trees, species of such importance both  to the earth and humanity. 

But here's a couple of random discoveries:

Why , Father of the forest Pan,
Neglect thy ancient care;
Resume, as when thy reign began,
Nor let our cliffs be bare.

O! nurse thy Britain's native plant,
Its stems of silver rear;
Nor let her sons, in future, want
The streams that once were dear.

Her birchen shades, in days of yore,
Were seats of sages' knowledge;
Where Britons heard the oral lore,
Ere yet was known a college.

The beginning of "The Birch", by Richard Llwyd (1752 - 1835, aka "The Bard of Snowdon"), a poem that becomes less lyrical but funnier as it goes along. I suppose the deforestation he's referring to was connected with the industrial revolution. 

Hängbjörk (Weeping Birch), watercolour by Karin Boye (1900-1941), probably in her teens

(Hängbjörk is Betula pendula, of course. The more common name in Sweden is Vårtbjörk: referring to the frequent nodules on the twigs, like the former scientific name Betula verrucosa.)

red in the willow crowns    plum in the birch

patterns of gnats     looked for a language

larger than us     tremor of catkins

folds of a bud    for meaning like runes

harder than answers   length in the light

the over and over of wood pigeon music

An extract from Lucy Ingrams' Light-Fall (2019), found in a review by David Caddy in Tears In The Fence

Silver Birch (Betula pendula). Frome, 1 February 2021.

Downy Birch (Betula pubescens). Frome, 3 February 2021.

These pictures show one of the other differences between the trees. Silver Birch has attractive silver-white bark, which as it ages develops diamond-shaped fissures, so the bottom part of the trunk becomes rugged and not white at all. The bark of Downy Birch stays more intact. It's quite a dull greyish white, even before it's covered in green algae like this one is. (Gardeners these days will probably be directed to the lovely Himalayan Birch Betula utilis var. jacquemontii, which has brilliant white bark, e.g. in cultivars like 'Doorenbos'.)

A young, very red-barked Betula pubescens. Chapmanslade, 9 February 2021.

Downy Birch (Betula pubescens). Frome, 2 November 2021.

This fine tree, anyway, can't be an accidental planting. It's one of a line of  half a dozen Downy Birch trees in Bath Road, opposite Frome College. 

Downy Birch (Betula pubescens). Frome, 2 November 2021.

Leaves and fruit of Downy Birch (Betula pubescens). Frome, 2 November 2021.

You can see the down on the birch here, too!

Bark of mature Downy Birch (Betula pubescens). Frome, 2 November 2021.

Bark of mature Downy Birch (Betula pubescens). Frome, 2 November 2021.

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