How fitting: It’s the 50th anniversary of Earth Day. My vegetable garden beckons. And wouldn’t you know it, I have an earworm.

Rest easy, it’s not one of those squirmy little devils that invades your cucumbers, squishes your summer squash or cuts your cherry tomatoes off at the knees.

No, sir. An earworm is a song that, for whatever reason, burrows its way into your brain and stays put, spooling endlessly as you go about your daily routine.

As Srini Pillay put it in the Harvard Medical School’s health blog a few years ago, earworms sometimes “show up when you are stressed about having too much to think about. It’s as if your stressed-out brain latches onto a repetitive idea and sticks with it.”

Sound familiar?

My earworm is “The Garden Song” by longtime Maine folksinger David Mallett. It’s an ode if ever there was one to the simple pleasure of going outside, getting down and dirty and, with a little luck, eventually putting fresh food on the table.

If you’ve never heard it, you’ve been living under a rock:

Inch by inch

Row by row,

Gonna make this garden grow

All it takes is a rake and a hoe

And a piece of fertile ground

Inch by inch

Row by row

Someone bless these seeds I sow

Someone warm them from below

Till the rains come tumbling down

I started humming it last year as I turned a small patch of yard into what would eventually become a thicket of pumpkins, peppers, basil, peppermint, tomatoes, you name it – all planted way too close together, but delicious nonetheless.

I resumed humming it a few weeks ago as I scanned the detritus from last year’s efforts and resolved to do better this time around.

That’s also when I also decided to call Mallett, who still lives in his boyhood home in the Piscataquis County town of Sebec. It was there, one sunny afternoon in 1974, that the timeless tune first sprouted while Mallett helped his father cultivate and pull weeds in the family vegetable patch.

“I remember him out there working and I was out there helping him and then I just had this little flash and I ran in and grabbed a guitar and started that little chorus,” Mallett recalled.

A day or two later, while visiting with friends in Old Town, he added the verses:

And pullin’ weeds and pickin’ stones
Man is made of dreams and bones
Feel the need to grow my own
‘Cause the time is close at hand

And rain for grain, sun and rain
Find my way in nature’s chain
And tune my body and my brain
To the music from the land

Who knows how and why a song takes off?

Part of it, in the case of a 23-year-old aspiring songwriter with freshly tilled earth under his fingernails, was timing. The back-to-the-land movement was in full swing, led by Scott and Helen Nearing on their self-sufficient farm in Harborside. “The Garden Song” soon became an anthem for those in search of a simple, more sustainable life, away from the big-city crowds.

Another part was repetition. In addition to Mallett, musical artists from Pete Seeger and Noel Paul Stookey to John Denver and the Muppets went on to record the song over the decades, unveiling it for new generations along the way.

Then there was the song’s message. In the simplest terms possible, Mallett struck a perfect balance between nurturing the spirit and preserving the planet:

Plant your rows straight and long
Temper them with prayer and song
And mother earth will make you strong
If you give her love and care

An old crow watchin’ hungrily
From his perch in yonder tree
And in my garden I’m as free
As that feathered thief up there

“I always felt so lucky to be young in that period,” said Mallett, who turned 69 Tuesday. “I thought that was one of the most positive periods in American history.”

These days, like the rest of us, Mallett finds himself stuck at home. The COVID-19 pandemic forced him to cancel the six concerts he had scheduled between now and July. On the day we spoke, he was shopping for a different server to “up my internet speed” so he can start performing online rather than simply “post old videos and such.”

Seasoned folksinger that he is, Mallett finds himself vacillating between “resilience and hope” on the one hand, and “absolute despair” on the other. But he wonders on balance if, when this calamity finally ends, something good might come out of it.

Ironically, on this Earth Day, some good already has: Scientists the world over have detected significant drops in air pollution because of decreased industrial output and fewer planes in the air and vehicles on the road.

Most say that’s a temporary phenomenon at best, yet Mallett counts himself among those who sense that real, long-term social changes might be afoot amid all this working at home and social distancing.

“Maybe when we do congregate as a species, it will be for something celebratory, like concerts, theater, weddings, things like that – know what I mean?” he mused. “Rather than spend all that money going to the office every day, why can’t I leave my car in the garage and not burn any fuel?”

There’s a tune in there somewhere. Maybe “The Garage Song,” about the virtues of permanently parking the old gas guzzler and reverting to a quieter, cleaner, less congested ethos.

But all that will have to wait. That patch of winter-weary soil outside the bedroom window calls me once again, ready for another crack at the cycle of life.

I can also hear my earworm.

As Dr. Pillay, the Harvard blogger, noted, earworms can actually be therapeutic, leading to creativity and clarity of thought. What’s more, he wrote, “each time music repeats, you hear something different.”

He had that right. In the almost half century that I’ve been humming “The Garden Song” to myself whenever my knees hit the soil, it’s never felt more plaintive, more poignant, more providential than it does in this spring of 2020.

Enough ruminating. Enough wondering when, and how, this will all end.

Inch by inch, row by row, it’s time to make my garden grow.