The nearest heather to us is about ten minutes from the farm. You park at Glenlomond, walk through a thin belt of pines, and come out into Glen Vale with Bishop Hill on your right and West Lomond on your left. From there the path climbs to John Knox's Pulpit with heather on both sides for most of the way. We do this walk all year. In August the whole glen is purple, and by November it has gone back to brown and looks half dead. If you turn round on the way up you can see Loch Leven, and on a clear day you can pick out the farm.
For years I assumed that the smell of that walk was the smell of heather. Then we started making perfume, and I picked a sprig, crushed it and held it to my nose. I got almost nothing from it. It was slightly green and slightly dry, about what you would get from any small woody plant.
That sent us off to read about it, and this post is what we found.
https://www.alltrails.com/en-gb/trail/scotland/fife/john-knox-pulpit
The chemistry
Common heather, Calluna vulgaris, does give off scent molecules. The best measurement we could find comes from a 2020 study in New Zealand, where heather is an invasive weed. The researchers sealed living branches in bags, collected the air around them and ran it through a gas chromatograph. They identified 33 volatile compounds.
Plenty of those are familiar to anyone who works with fragrance. There is α-pinene, the sharp resinous note in pine needles, along with limonene (citrus), linalool (the soft floral part of lavender) and β-caryophyllene, which is dry and a little peppery. One of the most abundant was 1-octen-3-ol, sometimes called mushroom alcohol because it smells of exactly that.
So the ingredients for a smell are present. The difficulty is the quantity. Heather releases these compounds in tiny amounts, enough for an instrument to pick up in a sealed bag and nowhere near enough for a person standing on an open hillside in a breeze. On the Lomonds there is nearly always a breeze.
Two smaller points belong here. The same study found that emissions varied from site to site, apparently in step with the soil, so heather on one hill may be fainter than heather on the next. And what we call heather is really more than one plant. Bell heather and cross-leaved heath (the Erica species) grow among the ling and are sometimes described as a little more fragrant, though we have not seen that measured.
When chemists look at heather flowers for other reasons, what they find is mostly not volatile at all. A 2018 analysis reported plenty of flavonoids such as quercetin and kaempferol, plus tannins and vitamin E. These are the sort of compounds a plant makes to cope with sun and grazing, and none of them has a smell. As far as we can tell nobody sells a heather essential oil, presumably because there is too little in the plant to be worth distilling.
https://pmc.ncbi.nlm.nih.gov/articles/PMC7076469/
So what is the smell?
Most of it is the ground.
Soil bacteria, mainly a group called Streptomyces, produce a compound called geosmin as they break down dead plant material. It is the earthy smell of a freshly dug bed, and a large part of the smell of rain on dry ground. People are extremely sensitive to it. The usual figure is that we can detect it at a few parts per trillion, which puts it among the strongest odours we know relative to its quantity.
The upper part of Glen Vale is wet for much of the year. The path gets boggy, there is a burn running down from below the Pulpit, and cloud often sits on the top of the glen when it is clear down at the loch. Wet, disturbed, peaty soil is where geosmin comes from. When people say the hill smells good after rain, that is mostly what they mean.
Temperature matters too. Scent molecules leave a surface more readily when it is warm, and a Scottish hillside is not warm very often. Cold air mutes everything, heather included.
There is one place on the walk where you can test this. Just under the Pulpit there is a small flat area where the rock cuts the wind. Stand there for a minute and the smell builds up: damp earth, wet stone, grass, and something faintly resinous that may be the heather or may be what we carried up from the pines. It smells of soil far more than of flowers.
So what is the smell?
Most of it is the ground.
Soil bacteria, mainly a group called Streptomyces, produce a compound called geosmin as they break down dead plant material. It is the earthy smell of a freshly dug bed, and a large part of the smell of rain on dry ground. People are extremely sensitive to it. The usual figure is that we can detect it at a few parts per trillion, which puts it among the strongest odours we know relative to its quantity.
The upper part of Glen Vale is wet for much of the year. The path gets boggy, there is a burn running down from below the Pulpit, and cloud often sits on the top of the glen when it is clear down at the loch. Wet, disturbed, peaty soil is where geosmin comes from. When people say the hill smells good after rain, that is mostly what they mean.
Temperature matters too. Scent molecules leave a surface more readily when it is warm, and a Scottish hillside is not warm very often. Cold air mutes everything, heather included.
There is one place on the walk where you can test this. Just under the Pulpit there is a small flat area where the rock cuts the wind. Stand there for a minute and the smell builds up: damp earth, wet stone, grass, and something faintly resinous that may be the heather or may be what we carried up from the pines. It smells of soil far more than of flowers.
https://en.wikipedia.org/wiki/Geosmin
https://chem.hbcse.tifr.res.in/wp-content/uploads/2024/08/Geosmin-English.pdf
When heather does smell
There are a few situations where people have always said heather is fragrant, and they fit the chemistry rather well.
The first is indoors. Heather was used for bedding in Scotland for a very long time. Traces of it were found at Skara Brae in Orkney, which is around five thousand years old, and Highland accounts describe heather mattresses packed with the flowering tips uppermost and say they smelled sweet. A mattress contains a lot of heather, dried, in a closed room, warmed by whoever is lying on it. Those are close to the conditions inside the researchers' sealed bag.
The second is fire. Heather moorland has been burned in rotation for centuries to bring on new growth, and anyone who has been near muirburn knows the smoke has a sweet, heavy smell of its own that carries a long way.
The third is drink. Heather tops were used to flavour ale in Scotland long before hops arrived. Robert Louis Stevenson wrote a ballad, "Heather Ale", about the last Picts dying rather than give up the recipe. One or two Scottish breweries still make a version.
Heather was also used for thatch, rope, brooms and dye. Almost none of its traditional uses depended on how it smells.
https://www.mdpi.com/2223-7747/11/15/1993
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12485031/
https://link.springer.com/article/10.1007/BF01332942
A note on Burns
We wanted a line of poetry about the scent of heather to put at the top of this post, and we went looking in Burns. We could not find one. Heather is all over his songs, but he tends to give it a colour or a season. In "Now Westlin Winds" (also printed as "Composed in August") the moorcock springs "amang the blooming heather". Elsewhere there are heather bells and moors red with bloom.
We have not read every line he wrote, so we will not claim he never mentions the smell. But when Burns wants a scent he usually reaches for something else, such as hawthorn, birch or new hay. He worked outdoors for most of his life and wrote about what he noticed, and the smell of heather does not seem to have been high on the list.
https://www.gla.ac.uk/media/Media_1209435_smxx.pdf
Bees and honey
Bees do very well out of heather even if our noses do not. One recent paper estimates that the heathers account for about a third of all the nectar produced in the UK. Scottish beekeepers still move their hives up to the moors in late summer to catch it.
The honey is strange stuff. Ling heather honey sets to a jelly in the comb and only turns runny when it is stirred, then sets again when left alone. The property is called thixotropy and is put down to the unusually high protein content. It means the honey cannot be spun out of the comb in the normal way and usually has to be pressed, which is one reason it costs more. It is dark, strongly flavoured and slightly bitter. Dioscorides, writing in the first century, thought it a poor honey. Present-day buyers disagree with him.
Heather honey also carries a chemical marker. A compound called dehydrovomifoliol, derived from pigments in the flower, turns up at 56 to 264 milligrams per kilo in heather honey, against 6 at most in the other honeys tested in the same study. Laboratories use it to check that honey sold as heather honey is genuine. The compound itself has no smell.
There is one more finding we liked. Heather nectar contains a substance called callunene, which has been shown to protect bumblebees against a common gut parasite.
What perfumers do instead
There is a version of heather in perfumery. It is described - when the fragrance industry characterises Calluna vulgaris as an ingredient - as a sweet and aromatic honey floral. Not the plant in open air, but the plant's concentrated chemical signature: the linalool and linalyl acetate threading through it, the honey quality from compounds shared with the nectar the plant produces for bees, the warmth that volatility and concentration can restore to something that disperses in the wild.
This is, in a sense, what perfumery always does with landscape: you cannot bottle a hillside. What you can do is find the molecules that carry the character of that hillside - the warmth, the sweetness, the particular quality of its light and season - and work with those.
In Cherish the Bee, we describe this as a Honeyed Highland Floral. The name holds two places at once: the heather moorland of the Lomond Hills and the wildflower meadow at Tarhill Farm itself, where the bees actually work. The honey character in the perfume comes from both - the moorland above, and the meadow below.
It is, in its way, a more honest story than a heather soliflore (soliflore = single-note perfume) would be.
What that means for a perfume
Perfume houses do list heather as a note, and it is generally described as sweet, honeyed and floral. Since no heather oil is available, the note is built from other materials. It is an impression of the plant in bloom, and much of that impression comes from honey.
That is the route we took with Cherish the Bee, which says "Honeyed Highland Floral" on the bottle. It has no heather in it. The notes are honeycomb, vanilla, wildflowers and cinnamon, and the idea came from two places, the heather on the Lomonds and the wildflower meadow we keep at the farm, which is where you will find most of our bees on a warm day. It seemed more truthful to make a perfume about the honey than to pretend we had captured a flower with so little scent.
https://en.wikipedia.org/wiki/Calluna_vulgaris
Back at the top
A last word about the Pulpit itself, since it is where the walk ends. The rock is a pale sandstone laid down as desert dunes in the Devonian period, and you can still see the thin stripes left by wind-blown sand. Geologists named the formation after it. John Knox almost certainly never preached there. The name comes from the Covenanters, who held outlawed services in the glen in the late 1600s because it was out of sight. Part of the outcrop fell in 2004 and the council took down what was left of the loose rock, so it looks less like a pulpit than it does in old photographs.
We still stop there every time. The heather is all round you at that point, and if the wind drops you will smell wet earth, cold air and a trace of pine. The heather contributes very little to it, at least to a human nose.
http://www.fhithich.uk/2022/10/29/glen-vale-and-john-knoxs-pulpit/
