Ten minutes frae Tarhill Farm, the road gies wey tae track, an the track gies wey tae open muirland. The walk up tae Glenlomond begins wi a fringe o pine trees afore the trees thin an disappear, an the Lomond Hills open oot on either side: Bishop's Hill on the right an West Lomond on the left. Frae here tae Knox's pulpit, the path rises through heather. It lines the trail in baith directions, stretchin intae the valley that flows beneath West Lomond, a sea o purple in late simmer, an broun an wiry in the winter. The fairm an the siller o Loch Leven is visible ahint ye as ye climb.

It's ane o the definin images o Scotland. Yet, if ye stop on that path an breathe in deliberately, seekin the smell that the image promises, ye'll be left wantin.

We've looked intae this an hope we can clear up the mystery.

https://www.alltrails.com/en-gb/trail/scotland/fife/john-knox-pulpit

What does the chemistry actually tell us?

Calluna vulgaris - common heather - dis produce volatile organic compounds. Scientific analysis usin gas chromatography has identified mair than thirty o them in heather's headspace, that bein the airspace immediately surroundin the plant. They're organised intae several chemical classes: fatty acid derivatives, monoterpenes, sesquiterpenes, an a wee group o alcohols an aldehydes.

The monoterpenes are the maist recognisable tae a trained nose. α-pinene - the sharp, resinous backbone o Scots pine - is present. Sae is β-pinene, limonene (clean, an citrus-like), linalool (herbaceous an lavender-like), an β-myrcene (warm an slightly green). These arenae rare compounds. They're some o the maist widely used molecules in perfumery. If ye could somehow concentrate heather's output an smell it in isolation in a laboratory, ye'd find somethin recognisable: faintly floral, lichtly resinous, wi a clean herbal thread.

The sesquiterpenes add some depth tae the cocktail: β-caryophyllene brings a dry, faintly spiced woodiness. Germacrene D is green an earthy. There's even 1-octen-3-ol in the mix - a compound mair associated wi woodland fungi, givin a faintly mushroomy, forest character.

The problem is volume. Heather emits these compounds at concentrations that are meaningful in an enclosed laboratory but vanish near-enough instantly in open air. The moment wind moves across the muir - which in the Lomond Hills is mair or less aye - the scent dissipates afore it reaches ony human nose.

There's also a species question. Calluna vulgaris, the dominant heather o Scottish uplands, is botanically distinct frae the bell heathers - Erica cinerea an Erica tetralix - that sometimes grow alangside it. The Erica species are a wee bit mair aromatic, but Calluna's the ane carpetin the hillsides, an its scent profile in the open air is essentially undetectable.

An yet, everyone wha's walked a Scottish muir returns wi a sense memory o it. The smell is real. It's just no comin frae the heather.

https://pmc.ncbi.nlm.nih.gov/articles/PMC7076469/

Whit the muir is actually made o, olfactorily speakin

Continuin on oor walk up the Glenlomond valley, whaur the path narrows an the cloud tends tae gaither, the air changes. A wee burn runs close tae the rock beneath Knox Pulpit. When the valley top is misty - as it often is, wi cloud sittin low ower the hills while the fairm's still in sun below - ye're walkin through the conditions that release ane o the maist potent olfactory compounds in nature: Geosmin.

Geosmin is a bicyclic alcohol produced by bacteria in the soil - primarily Streptomyces species - as they break doun organic matter in the peat. Its name comes frae the Greek: ge, earth; osme, smell. It's the compound responsible for the scent o rain on dry grund, a phenomenon named petrichor. An the human nose is extraordinarily sensitive tae it: we can detect geosmin at concentrations as low as five parts per trillion - mair sensitive than a shark detectin blood in water.

When moisture hits peaty muirland soil - when rain falls, or mist descends, or a burn disturbs the grund - geosmin lifts intae the air. It's the smell o the ancient organic matter (the soil) that's been accumulatin decomposed vegetation for thoosands o years. On a wet March mornin on Glenlomond, it's everywhere. It's usually whit folk mean when they say the muir has a smell.

Then there's the air itsel. Scottish upland air carries cauld an moisture even on dry days, an that absence o warmth changes hoo we perceive whit little scent is present. Smell is partly a function o volatility - warmth drives molecules aff surfaces an towards the nose. In cool, movin air, awthing's dialled doun. The few molecules heather dis release disperse faster. Whit ye micht notice instead is the quality o the air: clean, slightly mineral, the faint pine resin frae the trees at the bottom o the trail still lingerin at the base o yer sense memory.

In the hollow just beneath the rock, whaur the wind briefly drops, somethin changes. Wi'oot constant dispersal, the accumulated scent o the muirland - geosmin frae the soil, the faint green-resinous signature o heather an grass, the cauld mineral quality o the burn nearby - becomes briefly perceptible as a hale. It's no floral or sweet, but rather earthy an clean.

https://www.compoundchem.com/2014/05/14/thesmellofrain/ https://en.wikipedia.org/wiki/Geosmin https://chem.hbcse.tifr.res.in/wp-content/uploads/2024/08/Geosmin-English.pdf

Burns saw it. He didnae smell it.

Robert Burns catalogued the Scottish natural world wi mair precision than almost ony writer afore or since. In 'Composed in August', he records the westlin winds, the bloomin heather, the moon risin bricht - placin the poet in landscape, usin specific observation tae open intae psychological reflection. The poem's full o sensory detail, but the heather, as it aye dis in Burns, appears as colour an visual presence.

He disnae describe hoo it smells. No aince, in aw his nature writin, dis Burns attribute an odour tae heather itsel. He was accurate. Whit he wrote aboot, olfactorily, was the landscape roond it: rain on soil, turned earth, the scent o rivers an meadows an nicht air. The heather was whit he saw, but the smell cam frae underneath it.

This is a significant, an often overlooked, distinction. The romantic mythology o Scotland has collapsed the visual an the olfactory intae a single sensation: heather, an by implication the purple muirland, must smell o somethin. It must carry the scent o the place. But the maist attentive reader o that landscape, Burns, a man wha spent maist o his life wirkin in it, never made that claim.

https://www.gla.ac.uk/media/Media_1209435_smxx.pdf

Whit perfumers dae instead

There's a version o heather in perfumery. It's described - when the fragrance industry characterises Calluna vulgaris as an ingredient - as a sweet an aromatic honey floral. No the plant in open air, but the plant's concentrated chemical signature: the linalool an linalyl acetate threadin through it, the honey quality frae compounds shared wi the nectar the plant produces for bees, the warmth that volatility an concentration can restore tae somethin that disperses in the wild.

This is, in a sense, whit perfumery aye dis wi landscape: ye cannae bottle a hillside. Whit ye can dae is find the molecules that carry the character o that hillside - the warmth, the sweetness, the particular quality o its licht an season - an wirk wi those.

In Cherish the Bee, we describe this as a Honeyed Highland Floral. The name holds twa places at aince: the heather muirland o the Lomond Hills an the wildflower meadow at Tarhill Farm itsel, whaur the bees actually wirk. The honey character in the perfume comes frae baith - the muirland abune, an the meadow below.

It is, in its wey, a mair honest story than a heather soliflore (soliflore = single-note perfume) would be.

The view back doun tae the fairm

Frae near Knox Pulpit, on a clear day, ye can see across the valley tae Loch Leven an the fairm below. The heather's aw roond ye, daein whit it dis best: providin cover for grund nestin birds, nectar for bees, colour for a landscape that would look stripped wi'oot it. In flower, in August, it's purple tae the horizon. In November, bare an dark, it forms the texture o the hill itsel.

Whit ye smell, if the wind drops an the mist is in, is Scotland: the deep geosmin o the soil, cauld mineral air, the memory o rain. But, I'm afraid tae say, no the heather. Rather, the earth the heather grows frae.

This isnae a disappointment. It is, if onything, a mair interestin answer. The plant that represents Scotland mair than ony ither is, in terms o scent, almost entirely absent frae the experience o the Scottish landscape. The smell is elsewhere - in the soil, the sky, the moisture, the ancient organic matter underfoot. Scotland smells o its depth, no its surface.

Heather just shows ye whaur tae look.