Don't eat Yellow Snow....

Are we having a white Christmas?

Do we EVER have a white Christmas?

Well, no. We don't.

But here's a seasonal article anyway, for those of you who are so bored on Christmas Day that you have nothing better to do than come here and see if I have posted anything new. You are so sad! But who cares, it's Christmas! And if you'd rather be quietly reading, than arguing about who forget the sprouts, how many glasses of sherry Aunt Bertha has drunk, or what idiot invited the world's most boring relative to come and stay.... well, who can blame you.

So, "Don't eat yellow snow", then.

Yes, we all know that old so-called "Eskimo" joke - you know the one, what is the first thing that Eskimos teach their children: answer, don't eat yellow snow.

(Because someone or something has pee'd on it, of course.)

Well, it's a sound philosophy for life, and although we don't often see snow in the UK, there is one rather strange appearance of yellow snow, which you might like to keep an eye out for: the current cold snap has suddenly ended, which is quite a relief to those of us who work outdoors for their living, but we may yet have snow in January, or February... and when it does arrive, this is something you can look out for.

Here's some I found, a couple of winters back:

Mmm, yummy, look at that lovely yellow snow.

As it was in a bank of what I call Municipal Planting, on the way to the shops - ah, those happy, carefree days, when we used to just walk down to the shops whenever we felt like it, before Covid-19 hit, and turned us into a nation of hermits, not leaving the house other than for necessary journeys: shopping being necessary, but not in person: no, these days it's all click & collect, minimum contact: or delivery, if you are lucky enough to get a slot.

Where was I? Oh yes, those happy days when we could just stroll down to the shops for a couple of bits and pieces, whenever we felt like it.

So, this area being on the way to the shops, I assumed at first that it was just some dirty bugger having a pee: maybe on their way back from the pub, the previous night.

(Ah, yes, remember those days when the pubs were open, like, all the time.... I can't actually remember the last time I went into a pub...)

But when I looked up into the canopy:

Can you see it?

The snow lying on top of the branches, snow which has not yet fallen to the ground, is also yellow.

Huh?

How did somebody pee on that, way up there?

The answer is, of course, that they didn't.  

The secret lies in the species of tree: it's a common Alder, proper name being Alnus glutinosa, and it's a frequently-planted street tree. It's particularly popular as a municipal planting alongside streams or brooks, because Alder is one of the few trees that can tolerate having its roots in water.

How do I know that it's Alder? 

Well, the obvious answer is that I am a professional gardener, I have a diploma in Botany,  and for many years I have taught Tree ID, so it is kind of my specialist subject. *laughs*

  The less obvious answer is "catkins and cones" because Alder is one of the few deciduous trees which has cones, and these cones are often still available to be seen on the tree, right through the year.

This photo, left, was taken in January of this year, and shows the new male catkins, almost fully opened, with the previous year's female cones still on the tree, although now brown and empty of seeds.

 

In early summer the cones start to form, little green things in bunches of anywhere between three and seven or eight: by autumn they've turned woody, and are a dark brown colour: and they tend to stay on the tree right the way through to the following year, indeed you can often find fresh green cones growing, with the previous year's old brown ones still in place next to them!

And that's the reason for the yellow snow: the cones contain a lot of tannins and chemicals called humins.

This makes the cones very desirable for owners of aquariums, and apparently Alder cone sales is a big thing, in the fish-keeping world:  the humins release nitrogen, phosphor and sulphur, all of which help the occupants, including the plants, to grow: whereas the tannins kill germs, and apparently do a really good job of making the water crystal clear although at first, they stain it black, which sounds a bit scary, but presumably the black colour soon disappears.

Who would have guessed?

But it's the tannins which create the yellow snow: in the same way that tannins in tea leaves make our tea that nice deep brown colour, the tannins in the cones are washed out by rain, dew, moist air, and of course by snow. and they stain the snow yellow.

 So now we know - but "don't eat yellow snow" is still good advice - and in the meantime, Merry Christmas to you all!

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