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Can you help me figure out this (minor) mystery? (piefed.social)

submitted 1 month ago* (last edited 1 month ago) by ExtremeDullard@piefed.social to c/finland@sopuli.xyz

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Hey all,

I've been in Finland for 6 years and I have a lingering question that seems surprisingly difficult to answer.

Whenever fall arives (aroud now), and also sometimes in spring, certain places fill up with this unmistakable "fresh" aroma that's so typical of boreal forest. I've smelled it when I lived in Canada too. This smell is half the reason why I moved here: I just can't get enough of it. It's not pine: it's rather subtle most of the time when it happens. I'm 95% certain it comes from the birth trees (koivu) when the temperature swings wildly - typically in spring and fall.

I'd like to know for sure it's the birch trees that emit that smell, because then I'd plant a bunch of them on my property. But here's the thing: I'm not entirely sure it's birch trees, because none of the artificial koivu scents I bought manage to smell anything remotely close to that - if that's what they're trying to come close to.

And here's the mystery: when the smell arrives and fills the air, I ask people around me and if they know what that smell is. And almost nobody I ask seems to be able to smell it at all! The best answer anyone's ever given me once was "It smells like winter coming", which is not terribly botanical 🙂

I chalked it up to the locals having lived here all their lives and having become nose-blind to that smell. But I recently invited friends from abroad, and they can't smell it either.

I'm beginning to think being able to smell that smell is a genetic trait - like certain cats being totally unaffected by catnip.

Do you know what smell I'm referring to ? And if you do, can you confirm it's koivu?

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[–] Lumisal@lemmy.world 4 points 1 month ago (2 children)

I know the smell you mean.

I think I remember reading it's produced by some kind of bacteria, similar to petrichor. They'd why it's strongest in autumn and spring - the wettest seasons that also have cooler temps.

It smells similar to mountain jungle, just more fresh and less sweet, and I remember that same book saying that different wet regions have different distinctive smells because of the soil bacteria.

This was about 20 years ago, so I don't remember the title of the book at all, but maybe searching for that can help.

It could be, if it is soil bacteria, they hang out more around birch than other trees.

If this is the case though, it would probably take a couple years of planting many to get the smell near your house strongly, though I imagine using forest soil near birch would help speed up the process.

You could probably also test if this is the source by disturbing some forest soil with a shovel to see if it momentarily intensifies, maybe 🤔

[–] ExtremeDullard@piefed.social 2 points 1 month ago

Interesting, thanks! I certainly will look this up.

You could probably also test if this is the source by disturbing some forest soil with a shovel to see if it momentarily intensifies, maybe

Ideally, I would like to drag one of the students working at Oulu University's botanical garden outside when the smelll happens to ask them what it is - assuming they can even smell it at all, which at this point I'm not convinced everybody can. But that's unlikely to happen 🙂

Next best thing will be indeed to see if it comes from the soil. Even without disturbing it, if it comes from the ground, it should smell more strongly closer to the ground. That would be a good indication.

If this is the case though, it would probably take a couple years of planting many to get the smell near your house strongly, though I imagine using forest soil near birch would help speed up the process.

I have about 1500 square meters of forest at the back, and it's completely natural forest ground and shrubs there, and maybe 30 pine trees. But 10 of them need felling and I want to replace a few of them with birch tree, because I like birch trees better visually regardless of what they may or may not smell. But if they are indeed the source of that smell, I might fell more pines and plant more birch trees.

The lumberjack is coming in October to fell the trees. That's why I'm trying to figure out whether it's worth planting more birch now.

[–] tuukkah@sopuli.xyz 2 points 1 month ago

TIL petrichor: the earthy scent produced when rain falls on dry soil https://en.wikipedia.org/wiki/Petrichor

[–] tasankovasara@sopuli.xyz 3 points 1 month ago* (last edited 1 month ago) (1 children)

My wife has an acute sense of smell and she suggested 'worm smell' - the earthy smell that happens when the ground is wet and you're likely to spot earthworms (I must have taken in the smell of earthworms as a kid, since I know they have a particular smell to them, and I know what she's talking about).

Then again, birch does have an aroma to it as well. We have a pile of birch branches in the back yard from felling one in the winter. Definitely smells particular. Take a whiff of a birch sauna whisk and you'll have a representative sample!

[–] ExtremeDullard@piefed.social 2 points 1 month ago

It's not that. I know earthy smells. I used to spend a lot of time outdoors, and I've smelled earthy smells in all the countries I've lived in. The mystery smell I'm interested in is only found in boreal regions.

Take a whiff of a birch sauna whisk and you'll have a representative sample!

Hmm, I did buy a sauna birch whisk in a cheap discount store once (wrapped in plastic and all) and it didn't smell of anything. But now you have me curious again: maybe it truly was too cheap a store. I'll go get another one tomorrow.

[–] alzymologist@sopuli.xyz 2 points 1 month ago (2 children)

Are you sure it's not https://fi.wikipedia.org/wiki/Suopursut

Check it out, but don't overdo it, it's quite toxic. I do smell it mostly now and in spring. It's so nice I want to make beer with it instead of hops, although it's indeed poisonous, in small dosage it should just make things more relaxing. I'm quite sure it was used for this purpose historically.

Birch mostly smells with sap, first it's sweet and barely anything, then it starts fermenting.

And then you might be one of us smelling mushrooms. Pretty much all people of slavic origin are in this group I think. It is a pleasant thing, but then you find yourself on your knees with freezing wet fingers and full container of mushrooms that will take all your evening to clean.

[–] tasankovasara@sopuli.xyz 4 points 1 month ago

I too want to put some in beer 😁 Never had the courage to dose a 20+ liter run with it, but I've had some flowering suopursu in the sauna stove water to get a feel for how much is a little bit... It's three flowering branches 😋

[–] ExtremeDullard@piefed.social 2 points 1 month ago (2 children)

Are you sure it's not https://fi.wikipedia.org/wiki/Suopursut

I doubt it because one of the place I smell this smell most strongly when the conditions as right is right downtown Oulu where I live, and whenever I smell it and I look up, sure enough, there are birch trees nearby. And the city seems to have planted quite a lot of them - but also another variety that I can't identify, and it might come from that tree too.

But no suopursu anywhere in sight.

And then you might be one of us smelling mushrooms. Pretty much all people of slavic origin are in this group I think.

I'm not of slavic origin 🙂 The closest to a slavic country I can trace back my ancestry is Prussia. But yeah, I do smell mushrooms. I was quite the mushroom picker when I was a kid. Unfortunately, I don't know any of the varieties here, so I don't dare pick them. I need to learn them one day.

[–] alzymologist@sopuli.xyz 3 points 1 month ago

And also fallen leaves, that pretty much smell of fungi when they start decomposing.

[–] alzymologist@sopuli.xyz 2 points 1 month ago

Yeah, I don't mean that it's only slavic thing, I just know not everyone feels it and that it's certainly widespread in cultures that are quite obsessed with mushrooms.

Right now is the best fruiting time for typical birch mychorrizal species; and in spring, the soil-snow interface full of very fast decomposing mycelia gets exposed and smells strongly, as well as morel-like fruiting bodies.

If this is the case, planting birch would be a good idea. It's a good idea anyway. Just keep about 20% of conifers to leafed trees ratio to balance things out.

[–] tuukkah@sopuli.xyz 2 points 1 month ago (1 children)

In Helsinki, I smelled the autumn about a week ago and was wondering whether it would be from the linden trees because those have a strong aroma otherwise as well. There aren't many birches nearby here, but it could also be from broadleaf trees in general.

[–] ExtremeDullard@piefed.social 2 points 1 month ago

I've not seen any such trees in Oulu, or in the forest where I've smelled the smell. You might also have a different "smell of autumn" experience down south 🙂