Canadians seem to have this mad optimism about spring that even winter's lingering March grip can't shake.

I have seen sensible Canadians break out the shorts while patches of snow still cover the ground, well before the sun's orbit crosses the equator during the vernal equinox, which occurs on March 20 this year.

No matter that our suddenly bared bodies must endure that uptick in the wind chill factor this time of year, we remain, with good reason, optimistic, well-behaved Dionysian celebrants. That is our Northern nature.

In fact, with barely a speck of green in sight, many of us start thinking of gardening. We might not be able to beat the Taliban. But once a year, at least, we throw down the gloves at Old Man Winter.

The poetry of cultivation

Stanford professor Robert Harrison (Courtesy Robert Harrison)

For humans, gardens have both real and imaginary benefits. We have turned to them for consolation and earthy, dirt-under-the-nails exercise. As Robert Harrison tells us, these precincts may be as far away as Gilgamesh's garden of the Gods or as near as our own backyard.

Robert Harrison is author of Gardens: An Essay on the Human Condition. He is a professor of literature at Stanford University, a Dante scholar and a radio host (with a wonderful podcast called Entitled Opinions).

He was also a recent guest on Ideas, talking about life, literature and gardens.

A great appreciator of gardens, Harrison is not a hands-on grower himself. Rather, a scholar with a poetic eye, he sees gardens as a sublime metaphor for the human condition and more.

Gardeners cultivate the soil, they do not consume it. That's Harrison's tidy verbal formula. It has at least 10,000 years of human know-how behind it.

Quoting the Czech writer Karel Capek, Harrison tells us that gardeners must put more into their gardens than they take from them. That's the moral economy of gardening.

A reliable generosity

For Capek and Harrison, gardening is not just an activity, it's a state of mind.

"The gardener is a year-round cultivator," Harrison says. Even during winter months, when their hands are idle, gardeners "cultivate the weather." They fret over "too much snow, too little, the spectre of black frosts, the bursts of sunlight that may cause the bushes to bud too soon."

Gardeners fret whether it's too warm or too cold.

Still, when the weather warms and their souls ripen, gardeners begin to do what is central to them. They care for the soil under their feet and the plants they tend.

As Harrison writes, nature (or God, if you wish) may be cruel to our solicitations, but "as every farmer or gardener knows, its cruelty is in fact only a temporary suspension of its otherwise reliable generosity."

The earth fulfills the promises of abundance. But human beings must reciprocate and remain responsible for the earth's perpetual care.

Every backyard gardener knows that you don't loot your vegetable patch. So, by extension, we shouldn't be exhausting and despoiling the planet. Do the little things right and big things will follow. It's an ancient piece of wisdom, found in any well-tended garden.

A moral education

That of course, is an easy sentiment for anyone to say, munching on an agribusiness apple at his computer (yum). We humans enjoy thinking these sublime thoughts, which make us feel good about ourselves while carry on with our carelessly consumptive lives.

That's why Harrison insists that gardening is not just a mere activity or recreation. At its core, gardening is a moral education.

For him, the act of gardening plunges us into our natural history. When you garden you "come to understand the efforts by which life forced a foothold for itself in a hostile and resistant clay."

"It was the labour of living organisms, fighting every inch of the way, that turned it (the earth) into humus."

In the beginning, the hard ground resisted all these pesky organisms, what Harrison calls "life's colonizing ventures."

But over millions of years, the "relentless metabolism of primitive bacteria" enriched the atmosphere with oxygen and carbon dioxide. Photosynthesis allowed plants to grow as they feasted on sunlight, water and air. Eventually, the whole planet was transformed into a "thriving garden of sorts." Call it a miracle. Or a fact of natural history.

Take care

Harrison, a scholar always on the verge of poetry, tells us that the principle of "care" is required for life to expand outward and that in so reaching life always "exceeds itself."

Organisms with no brain at all seem to understand the need to maintain the rich humus of the earth, rather than deplete the reserves of its vitality. So why can't humans?

Harrison is not telling us to stop fiddling with Mother Nature. He is saying that reckless consumption is not a natural biological ploy, nor is it in our long-term human interest. He wants us to understand the sheer abundance that has been given to us by nature over the course of the millennia.

Harrison tells us that life itself is a projection, a kind of sublime ecstasy that overreaches itself. Care, from the smallest microscopic creatures up to us humans creates our teaming biosphere. Be careful is his message.

It's wonderful, heady stuff. Harrison also has a warning for the non-gardeners among us.

One of the paradoxes of our age, he says, is that our craving for more life, more things, more experience, is driving us to turn our abundant globe into a consumer paradise that is a parody of the Garden of Eden.

We hunger after more stuff, more fruits of the land. So we assault creation itself. We think we want to create an Eden. But we end up turning our earthly garden into a desolate human wasteland in too many places.

Harrison is not a prude, mind you. There is nothing wrong with consumption, he says. But he wants the gardener's ethic to thrive, wherever we live.

The gardener understands the truth deep within nature's thumping heart: the more you take from the earth, the less you get in return.