The Sweet Smell of Soil can make you Happy
Julie Kilpatrick is going around sniffing soils. It’s not a weird obsession, it’s all in the name of research for her new book, The Plant City.
“I am always happiest when I’m around plants. In my first book, The Plant Listener, I wanted to help people connect with plants by understanding what makes them tick but the part of plants we see is only half the story. Plants go to work above ground but make their homes in the soil and they share their homes with whole cities of other living things, hence the title of my next book, The Plant City. It was while looking into the plants’ soil-dwelling neighbours that I discovered something fascinating. Suddenly, it made sense to me why I always feel so good when I’m gardening.”
That something fascinating came in the form of the tiniest of the plant city’s residents. A bacterium which lives in soil can actually alter the human mind, relieving stress and anxiety. Mycobacterium vaccae stimulates neurons and increases levels of serotonin, a neurotransmitter associated with feelings of wellbeing and happiness. And you don’t even have to get your hands dirty – just being outdoors can cause us to inhale this natural anti-depressant.
But Julie believes that, to achieve the most beneficial effect, you need to be around healthy soil:
“Soils rich in organic matter smell sweet and pleasant, while depleted soils don’t smell much at all. That’s because bacteria in soils survive by feeding on organic matter and some of them produce a substance responsible for that sweet smell, known as geosmin. If you can smell geosmin, you know you have a soil that is healthy and full of microscopic life and, very likely, the bacteria which makes us feel good will be part of all that life. Even if you don’t have a garden, all you need to do is to get outdoors and inhale healthy soil. One of the best places to find soils rich in organic matter is in wooded areas where the plants look after the soil and there’s little interference from humans.”
Speaking of the smell of geosmin, at no time is it more noticeable than when it rains after a dry spell. That sweet smell of summer rain has been given a name – petrichor – and it’s a mixture of geosmin disturbed by raindrops and oils exuded by plants during dry spells. Julie thinks its nature’s way of telling us it’s happy the drought is over:
“I don’t know anyone who doesn’t love that smell and the pleasure it gives us is so primitive. Our ancestors, who depended solely on soils for their survival, would have felt a tremendous sense of relief upon smelling petrichor and we have retained that feeling, even if we don’t quite know why.
Gardening has always been considered great therapy but now we know you don’t have to be a gardener to benefit. Just get yourself out there and feel the living, breathing, medicinal earth beneath your feet and, while you’re out there, pick up some soil and give it a sniff.”
Julie Kilpatrick is a lecturer in horticulture and author of The Plant Listener, a book which explores the lives of plants and explains the science behind our gardening practices.
The Plant Listener is published by Gardenzine Publications. ISBN: 978 1 9997243 0 6
The Plant City has an expected publication date of October 2019