Gardening good for health

Gardening feeds you in so many ways that 10 fingers aren’t enough to count them. Beyond the end results — the baskets of fresh food, bouquets of flowers and shady landscaped retreats — the work itself nourishes the grower.

When you are gardening, you are outdoors, breathing fresh air and soaking up vitamin D from sunshine. You keep moving, to the benefit of both mind and body, with muscle-building jobs such as digging and meditative ones such as weeding. The companionship of birds, toads and other wild creatures is there for you to enjoy, even in a city garden. Tension melts away, and when you survey your tamed, orderly plot at day’s end, you feel a quiet pride.

There’s another, somewhat mysterious dimension to a gardener’s pleasure, though, and that’s your partnership with a living soil. Ever since penicillin was first crafted from a soil fungus, the earth has yielded up agents of healing. As recently as January, researchers at Northeastern University announced a newly tested antibiotic produced from a soil sample that kills resistant strains of staphylococcus and tuberculosis. We can expect more discoveries like these to turn up, along with the more anecdotal stream of evidence that humans, both young and old, are somehow healthier if allowed to play outside in the mud.

The mind part of the health equation is equally promising. For some years now, researchers have been working on a soil microbe called Mycobacterium vaccae, which triggers mouse brains to produce serotonin and thereby acts as an antidepressant. A study done at the Sage Colleges in Troy, N.Y., showed that mice exposed to it had less anxiety, learned better and ran through mazes faster and more competently. Could gardeners’ grubby hands be absorbing homegrown Prozac?

Among gardeners’ pleasures, many would list the smell of the earth or, I should say, the smells. Warm and dry, it has one odor; warm and moist, another. The rich, fragrant soil of a greenhouse in deep winter turns it into a biosphere where spring has been captured and held.

In a class by itself is the smell the soil gives off after rain, especially if it has been dry. Whereas the dusty streets of a city yield a slightly acrid odor when rained on, the scent of soaked lawns or gardens is mellow and refreshing.

To me, it has always seemed like an expression of gratitude for thirst that has been quenched. Scientifically, the phenomenon is more complex. When rain falls, the increased moisture and the gentle pounding of the raindrops cause certain compounds to be released and combined in the air, one of them an odoriferous bacteria-generated substance called geosmin, and the other a group of oils that plants secrete to inhibit growth in dry weather. First noticed on clay (argillaceous) soils, where it is most pronounced, the soil-after-rain smell was originally spoken of as “argillaceous odor.”

In 1964, two researchers, the Australian Isabel Joy Bear and the Briton Roderick G. Thomas, gave it the less-restrictive name petrichor, combining petra, the Greek word for stone, with ichor, the golden blood that made the ancient Greek gods immortal. Were we more sensitive to the earth’s ways, we would no doubt have even more names for the many ways in which it breathes.