Ruairi, my lanky teenage son with blue braces and I decide to plant flats of Allium canadense on one of my favorite living roofs tonight. I set out promptly planting while Ruairi totes numerous trays up the winding spiral stairwell, both of us focusing on the unhealthy sub sandwich we are going to eat after completing our task at hand.
“Hey Dad!” Ruairi exclaimes loudly, “a green tree frog!”
Setting the Allium down I turn. ”They come up here to escape the larger predatory brown Cuban tree frog.”
“Same with the green Florida anoles, right?”
The memory of youth is amazing, something I am jealous of and I know my cell phone is laying near me somewhere in this rooftop jungle.
“I though you’d cut the roof plants back this weekend, Dad. It is still a jungle up here.”
“We cut hundreds of pounds of biomass off the roof Saturday morning, Ro.” Ro is easier to say than the Celtic rendition of his name, though most just call him ‘Rory’.
“Carbon sequestration, right?”
Florida Virtual School’s curriculum is thorough and I shake my head affirmatively, rubbing my nose with the back of my dirt encrusted hand. The pollen is thick on the roof and that is ok with me because the thick earthy scent of rooftop plants and soil is so comfortingly familiar. ”Yes. The plants we had breathed in so much carbon dioxide. During photosynthesis..”
Ruairi finishes my statement abruptly in the way teens do, “plants eat sunshine and take the solar energy combining carbon dioxide and water to create sugars and oxygen. Look, the tree frog is watching you, Dad.”
I nod again, continuing to plant, wanting to beat the setting sun, mind whirling with the complexity of it all, the kid, the green roof plants and the rooftop wildlife. ”These plants are cleaning the air and providing habitat for wildlife.”
“Uh-hunh”, he mumbles. ”Lots of different types of wildlife use the roof, don’t they.”
“Sure do, Ro.” Scooting around the plants I’ve just planted is not as easy as it was years ago but I am actually proud of the shape I am in for my fifty four years. ”My friend calls this plant ‘Indian’. Her real name is Bidens. But my friend calls it Indian because of all the little arrows you end up with all over your clothes.”
“You have strange friends, Dad. It’s amazing all this grows in so little dirt,” Ruairi comments.
“Fifty millimeters of Green Roof soil media,” I say quietly, waiting for the question.
“About two inches, right?” He surprises me, like always.
“Plants don’t need soil to grow. Soil holds trace nutrients for the plants the same way your bank holds your money for your use someday. What we do here, Ro, is create proven permaculture interactions. Because there is very little soil the Green Roof ecosystem must be constantly pulling carbon dioxide and nitrogen out of the air. The leaves falling from these surrounding trees and some of the biomass we harvest provide other micronutrients.”
Ro nods. He is squatting in front of the green tree frog. I lost him in the soil and nutrients thing. He is much more interested in the attentive tree frog.
“Aren’t you cutting down valuable habitat?”
“I’m not cutting biomass. I’m planting Allium, Ro.”
“I mean, the other day, Dad. Shouldn’t you have left the plants on the roof?”
I stand, stretch back my shoulders and try to move my half asleep leg. Yerba mate in my tall cup calls from the other side of the roof. “Harvesting the green roof biomass and composting the plants helps in the whole scheme of the carbon footprint thing, Ro. Hand me my yerba mate por favor.”
Ruairi leaves the amused and alert tree frog and brings me my tea. ”So harvesting the carbon is more important than habitat?”
“See all the cut plants down there? We estimated almost five hundred pounds of dried plant material. That’s a lot of carbon and the pile creates ground level habitat for wildlife.”
“How much carbon, Dad?”
“Probably several hundred pounds. Every little bit helps.”
“How much carbon footprint does your yerba mate have?”
“It comes from the store down the street” I shake my head. Teenager’s brains whirl faster than mine.
“I thought it came from South America.” Ruairi smiles.
“How about carrying those empty trays down to the truck and I’ll finish planting. Getting hungry.”
Why wouldn’t many someones want to create habitat and sequester carbon and nitrogen on all of the world’s roofs?
Final Allium is planted and the yarrow in front of me is dark and green and beautiful. It is late October and the roof is still alive with butterflies, bees, insects and of course the green tree frog. I sigh heavily, perfectly satisfied with my dirty fingernail role of creating green roof ecosystems in hot and dry climates.
“Hey, Dad,” Ruairi calls. ”Truck is loaded and I’m hungry.”
“Thanks for helping, Ro. Firehouse, Subway or Jimmy Johns?”
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