Country diary: smells like evergreen spirit
I love the smell of conifer resin in the morning. Here, on a skin-tingling frosty day, with the first rays of sunshine skimming the treetops, it scented the shadowy depths of the forest. In the original line from the film Apocalypse Now, the fragrance Lt Col Kilgore loved in the morning was napalm, and volatile secretions from these conifers share its sticky, explosively flammable properties. Indeed, heptane distilled from the resin of Jeffrey pine, Pinus jeffreyi, native to California, provides the zero point for octane rating, a measure of petrol’s resistance to exploding under compression.
Standing here, in a grove of mature Norway spruces, it was easy to see the trees’ trade-off for producing such a combustible product: dribbles of coagulating resin oozed from wounds on damaged trunks, sealing them from fungal infection and deterring opportunist insects. (Amber, fossil resin, often contains entombed insects that stumbled into its gummy grip.) Like blood in capillaries in human skin, resin is carried in ducts that ramify through living tissue, from inner bark to the slenderest needles, leaking whenever outer defences are breached.
In many conifers it has a distinctive fragrance. Foresters have told me that they could identify common species, eyes closed, simply with a “crush and sniff” test. I have tried it, but lack a scent memory trained by long experience.
Differences can be complex and subtle, hard to describe in the restricted vocabulary of fragrance, which relies on subjective analogies to familiar, everyday scents. A hint of grapefruit emanates from the soft needles of Tsuga heterophylla, at odds with the description of those who named it western hemlock, thinking that it smelled like poisonous hemlock, Conium maculatum.
Sensitive chemical analysis, using gas chromatography, can however provide a fragrance fingerprint of aromatic volatile compounds. One of the commonest components of resin is pinene, easily detected in the air in conifer forests on still, cold mornings. In 2015, biochemists in Japan measured a rise of pinene levels in the blood of visitors to conifer woodland: from under the bark of a tree to under the skin of a human within as little as 60 minutes. Maybe that’s why walking in this forest, inhaling this scented air, provided such a sense of wellbeing this morning.
