Leaving the house one dark, wet morning last week, I immediately noticed our maples had shed nearly all of their leaves overnight. Despite feeling a bit discouraged at all the raking I’d have to do, I couldn’t get over the wonderful smell that greeted me. It was like walking into the heart of a maple forest, full of the spicy, lusty leaf smell that becomes especially rich on a damp  morning. Like the dark-eyed juncos at the backyard feeder, the cool temperatures and the greys and browns of roadside goldenrods, the smell of sodden leaves on the ground signals November’s arrival. Gone are the heady days of early October with its riot of colour and still summer-like weather. We have moved on.

Appreciating nature is clearly not just about sights and sounds. It’s also very much about odours and even taste and touch. We need to bring all of our senses to the experience. For me, smell is an emotionally-charged sense that represents the promise of change – the barely perceptible slippage of one season or time of year into another.

As humans, we experience the  world primarily through eyes and ears. We tend to pay less attention to what our nose is telling us. It’s partly because our culture often teaches us that there is  something impolite or embarrassing about odours. Nor is smell a sense that we usually  need in order to survive. At the same time, however, smell allows for near instantaneous emotional connection to a situation. Without it, we feel isolated.

The human nose detects smells through millions of microscopic olfactory cells, located in two patches about the size of postage stamps on the roof of the nasal cavity. When odour molecules reach the cavity, they dissolve in a layer of mucous and are absorbed by hairs on top of the nerve cells. Differently shaped  cells “trap” different molecules – almost like a key fitting into a lock –  and therefore recognize different smells. The olfactory nerve then transports signals from the cells to the smell centre in the brain.

Humans can detect over ten thousand odours and have about five million of these olfactory cells. This sounds impressive until you discover that dogs typically have about 44 times more! Imagine the huge diversity of smells that a dog encounters and that are lost on us. Imagine the pleasures  we are missing. As much as our brains have expanded over evolutionary time, our sense of smell has shrunk. What a pity.

It is said that smell is our most ancient sense, and that it is wired deeper into our brains than even sight and hearing. This helps to explain why a few simple airborne molecules – as little as one part per billion – can trigger vivid recollections and strong sentiments. This is not surprising. Our sense of smell follows a pathway in the brain that is linked to the brain’s emotional and memory centres. That’s why we react so strongly to certain smells and either love them or hate them. It is also why smells can leave permanent  impressions that are strongly linked to past experiences. The smell of smoke from an outboard motor reminds me of wonderful fishing outings with my grandfather and is therefore an odour I like. I’m sure for most people, though, exhaust is not at the top of their smell list! More than anything, our reaction to smells is intensely personal.

Maybe part of the reason we tend to almost suppress or ignore our sense of smell is that our language to even talk about it is severely lacking. About all we have to work with are the names of the seven basic smell groups: minty (peppermint), floral (roses), ethereal (pears), musky (musk), resinous (pine sap), foul (rotten eggs), and acrid (vinegar). Beyond this, the requisite words don’t seem to exist. It’s as if we’ve never developed the proper vocabulary to properly describe the olfactory experience. In “A Natural History of the Senses” poet Diane Ackerman describes how hard it is  to explain how something smells to someone who hasn’t smelled it. “Lacking vocabulary, we are left tongue-tied, groping for words in a sea of inarticulate pleasure and exaltation.” Contrast this to our sense of sight where we have words for every shade and intensity of colour. When it comes to the tones and tints of a smell, however, we are left to devices such as awkward comparisons to something else, be it vanilla or wet dog hair. We also tend describe a smell in terms of our reaction to it – what a delightful (or revolting) smell!

We don’t need to sleep-walk through the olfactory world, however. The American naturalist and philosopher, Henry David Thoreau, elevated smelling to an art form. When walking in the woods, he would smell nearly every plant he encountered by constantly rubbing or crumpling the leaves, thereby releasing the aromas within. Many of the smells come from  volatile oils  that plants use to defend themselves from insects and other herbivores. For example, by squeezing the leaf of a prickly ash – a common species in the Kawarthas –  a flood of citrus odour is released. Prickly ash is a member of the orange family and has the same pungent, aromatic leaves as the orange tree. Thoreau also loved to  sleep on spruce boughs which he would pile particularly thick around his head and shoulders in order to indulge his sense of smell as he slept. Nor was he just attracted to the typical pleasant smells of nature. Thoreau even wrote: “I love the smell of the swamp, its decaying vegetation .”

Even today, Amazon Indians use smell to identify trees,  since features such as leaves, flowers and fruit can be hard to get at. They simply slash the bark with a machete and breathe in the tell-tale flood of odours that pour out.

By paying attention to nature’s different aromas, we can literally follow the progression of the seasons smell by smell and thereby feel further connected to the Earth’s endless cycles. I’d therefore like to propose an olfactory trip through the year of smells that represent for me the mileposts of the seasons. While most of the smells are pleasant, some rather disagreeable odours are included in my list as well, simply because they, too, signal the time of year.


Early fall

·         Freshly fallen leaves – the spicy smell of autumn leaves is one reason why fall is said to be the most nostalgic of the seasons

·         Burning leaves – this smell takes me back to sunny fall afternoons at my grandparents’ cottage where I spent hours raking and burning the leaves

·         Smells of the harvest – apples and the assortment of other fruits and vegetables at the Farmer’s Market

·         Wood smoke – the smell of the first wood fire of the fall is yet another nail in summer’s coffin

·         Wintergreen leaves – on fall walks, I love to stop and crush a wintergreen leaf for its strong, wintergreen scent. The leaves of this evergreen plant can also be chewed.

·         Fungi – most mushrooms do not have a distinctive odour. However, there are exceptions. Agaricus mushrooms smell like almonds, while some Marasmius species have a garlic smell. The golden chanterelle smells like apricots. The strongest odours, unfortunately, belong to stinkhorn fungus which smell like carrion and actually attract flies.

Late fall

·         Decomposing leaves – the smell of leaves being softened, shredded, digested and decomposed by countless billions of bacteria, fungi and invertebrates

·         Freshly cut wood – probably the best month to cut firewood, November brings the  smell of wood as the axe or chainsaw bites through a log. Some of my favourite wood smells are white pine, white birch (reminds of Tinker Toys) and eastern red cedar.

·         Manure – the smell of manure is often in the air as farmers spread it before the ground freezes

Early winter

·         A general lack of smell – an absence of strong smells is a characteristic feature of late fall and early winter. Much of the reason for this is because there are no plants in bloom.

·         Balsam fir – a balsam Christmas tree transforms the smell of the house and immediately evokes memories of Christmases past. The foliage of all the conifers exudes wonderful, resinous smells, especially when warmed by the sun on a mild winter day.

·         The smell of approaching snow – snow can contain many chemicals such as formaldehyde  and sulphate, all of which have distinctive odours, and can sometimes be perceived by the human nose. The nose is also sensitive to changes in temperature, humidity, and air pressure, all of which can signal that it is about to snow.

·         Smells associated with snow – Snow in itself may not have an odour, but it is definitely mingled with myriad other smells such as cross-country ski wax, smoke from a wood stove, and even snowmobile exhaust.

Late winter

·         Skunk spray – the smell of a male skunk on the prowl on a wet, mild February night is one of the first signs of pre-spring. It is an unpleasant but yet welcome smell that heralds the red-winged blackbirds’ arrival in a few short weeks.

·         Balsam poplar and yellow birch buds–  when I’m skiing or walking in the woods, I love to stop and  squeeze the resinous buds of a balsam poplar. They  give off the sweet, pungent balsam odour that is so common in the Kawarthas in May. For  a wonderful wintergreen smell, crush a twig or bud of a yellow birch tree.


Next week, I’ll continue my discussion of the signature smells of nature’s year with a look at spring and summer.


Categories: Columns

Drew Monkman

I am a retired teacher, naturalist and writer with a love for all aspects of the natural world, especially as they relate to seasonal change.