A Rooftop Garden Primer


Delivered as a TED-style talk at the Greater Portland Sustainability Educators’ Network symposium on Jan 27, 2017


Greetings, my name is Marc Boucher-Colbert

And I am here to tell you about a rooftop that once was bare

And the garden that now we’ve got

At a wine bar in town called the Noble Rot

It’s a building with an unusual crown of green

And yet which I sincerely hope becomes

In the words of today’s kids “dope”,

That meaning, more valued in the urban scene.


I first conceived of rooftop gardening on a lark,

One day I passed a white birch growing in a gutter,

Which provided the spark

to think of gardening elevated.

I then dedicated a portion of my master’s studies to making plants buddies with the sky,

And I’ll not lie….after ten years of rooftop growing

There’s more than meets the eye.


If by being versical I appear to temporize,

It’s not so; I’m merely poising to generalize

And speak not just about one roof, but about a move-ment

Called green roofing and though this lecture

May depart from the norm I hope it offers

Solid principles, form, and not just mere conjecture.


It was the Austrian architect, Hundertwasser, who said,

We’ve murdered the land, left it for dead,

When we’ve scraped it clean for building.

We have a duty, he declared, to be re-guilding the place we’ve bared,

Though not with gold but with green

In order to repair what was pristine.


As policy this turns out to be mighty good

For liveability, for the neighborhood,

You see, the living earth which we with concrete covered

Mothered us with kindly deeds,

Those mighty trees, those humble weeds

Cleansed the water, blithed the air

And when we knocked them down, we were left to wonder where

All those kindnesses would then come from.


Yet how to fix things when we’ve taken all the space

Left nary a trace of the place’s original charm.

Well, let’s consider the building’s form:

5 surfaces which are possible to transform

In reciprocity to Mother Nature.

Four walls, of course, whose vertical status

May partially put our green thoughts in hiatus,

Possible to green, but not so easy.

How about a horizontal plane that’s sunny and breezy?

The roof, I mean, which when relatively flat

Offers itself as a lovely plat

For biophilic building.


You can probably guess the benefits of such an approach:

We keep excess water from the sewers, keep poop from broaching

Our lovely rivers; the greenroof also delivers

Measurable reductions of the Heat Island Effect;

Takes pockets of habitat and connects them together.

It can even help moderate the weather by its evapotranspiration.

Now wouldn’t that give us healthier cities, make us a better nation?


And though the benefits of greening roofs are wide,

I’ll approach now from the agricultural side.

As urban centers grow and grow,

Hungry mouths multiply below.

And if we rely on food that’s trucked

From far away we’re clearly…sucked

Into delusionary thinking,

Which is a shame because we could be drinking from our own wells, so to speak.

Growing food atop the peaks of our urban ziggurats

Rather than eating the junk at 7-11 while smoking cigarettes.


But wait, it’s not as easy as throwing dirt high up above

And trusting that some kind of  groovy, hippie, green-plant love

Will take care of all the rest.

The naïve urban farmer will be distressed to hear of terms like

Suit and liability.

In truth there’s tremendous responsibility when gardening the urban big top

The less you know, the more likely your Big Flop.


So here’s a few pointers which may come in handy

If you’re contemplating growing something in some sandy soil atop your roof

The stuff weighs a lot, you don’t want to goof;

Otherwise, while trying to save the Earth, you may torpedo your own net worth.


The story begins with physics, I suppose,

Which governs a building from its head unto its toes.

There’s a fundamental fact, which we must attack and outright address.

When you put a load on top of a roof the structure will be stressed.

Something top-heavy is essentially unstable, yet we are able to account and to correct for that,

And so the potential green roof gardener must not loaf, must take a kind of Hippocratic oath

To do no harm to the building’s structure and, thus I ask you now to swear

That before beginning any project you talk to a structural engineer.


That kind of person is good at discursin’ on

Spans and joists and members, and after looking at the plans,

Will translate all the gobbledygook into a few single, necessary numbers.

That maximum allowable load will tell you if your roof garden intention bodes well

And then, if you’re thinking of putting something soil-like

Up on the roof you’ll have the numbers that prove you did it right

And did not overload.


Oh, did I mention you can’t go this road alone?  Plan to be on the

phone a lot as you explore your dream, with roofers, architects, the

building owner, basically your team.

The worst approach would to try to be a loner and not to acknowledge

that the roof’s a complicated place,

A space with too many faces for the would-be sky-gardener to alone embrace.

Go consult with your people before you try to cultivate the urban steeple.

Get opinions and agreements written down;

Proper documentation will prove that you’re no clown.

And even though you’re mostly interested in growing plants,

You’ll have to prove you wear the pants of other disciplines like engineering

To be taken seriously and thought of as pioneering.


The only other thing you must not do, is harm the roof

And by that I mean keep it waterproof.

For after all is said and done, your gardening project is lost or won

On preventing harm to the folks and property down below,

And a drip, drip, drip is a pretty fast way to get shown the door.

And just as with floors, there are so many different roofing products, all require that the gardener conducts him or herself with care,

To prevent the wear and tear of foot fall

And all the possibilities for a puncture wound

Good God, I swoon to think of what might happen if I errantly dropped a gardening blade,

Or, worse, if a spade strayed too deep and frayed the fabric of the membrane.

Even a tiny, filamentous plant root might craftily shoot through an asphaltic roof in search of drink.

And so in answer to these cold-sweat-inducing night-terrors, I think it wise

To learn and be advised on root barriers and roof surface protection.

Also recall various chemicals have a predilection to react with one another,

So know thy products and choose materials that are brotherly,

Not chemical enemies unto each other, please.


Now that I have done due diligence to prevent you from some blind-siding negligence.

There’s really not so much to say, save “How are your gardening skills?”

The main thrills from here are the ones shared by any horticulturalist,

And rooftop gardening will put you to the test,

Making you prove your mettle because you’re basically gardening in a kettle or a container,

And that, typically, a shallow retainer of 4, maybe 6, maybe 8 inches of medium

Don’t forget that when your plants start crowing for water and nutrients, you’re the one who will be feeding ‘em.

They really can’t forage much in 6 inches of soil and thus the toil will be mostly yours not theirs.

Rooftop gardening will provide much satisfaction

And your higher-altitude produce will be a star attraction among the city’s dwellers, the restaurateurs, the sellers of sustainability,

And although it may attain cliché in some distant urban future,

I don’t think we’ll see it soon passé because we’re going to need to nurture ourselves,

And we only have limited space to do it.

Our buildings will be put to it: that is, the greater tasks of healing the city’s defects while providing for the masses and absorbing greenhouse gasses.

Roofs that now pass for waste space will soothe the eye, put food on the plate.


So from my perspective, high atop the city.

I see a scene that’s looking rather pretty,

With elevated acres of urban greenery,

Providing jobs and produce while bettering the scenery.


I hope I’ve said enough to dissuade the faint of heart,

And yet a sturdy challenge is where the stoutest start.

Please join my cause; our aces won’t be Trumped.

Those who refuse to lead on this will certainly be dumped.

Hey, Hundertwasser, we’re finally ready to listen

And bring some life to buildings, recover what we’re missin’

We’ll take those wasteland acres hanging in the air, and make of them a chaste-land urban mountain fair.






















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