Naperville homeowner letting green roof, yard thrive

Periodically, someone walks up to Pat Armstrong's house and asks if it's for sale.

They see the myriad tall, rangy grasses sprawling across the corner lot -- nearly obliterating the house from view -- and assume the property's fallen into disrepair.

Sometimes a landscaper even drops off a business card.

Armstrong promptly sets them straight.

Yes, the yard's supposed to look that way, she informs them. It's an oasis of nature in a sea of manicured lawn neatness. Notice all those plants up on the roof? Those aren't just strays that have migrated out of the gutters. That roof's growing. Seriously.

Usually when people hear the term "green roof" they think a landscaping design atop a large building a la the mammoth Chicago City Hall project or one of the many smaller gardens that have popped up in the suburbs in recent years.

But they're always built on flat surfaces.

Armstrong's home at the corner of Staunton Road and Naper Boulevard has traditional sloped roofs.

And its own mini skyline prairies echo the yard.

Ever the educator, Armstrong, a part-time College of DuPage faculty member uses both her yard and the roof for her classes: prairie wildflowers, edible wild plants, landscaping with natural plants and gardening with wildflowers. It's the ultimate living classroom.

The city permits such towering eight-foot plants under an ordinance that allows "naturally landscaped lots" including wildflowers and native grasses, explained Ann Michalson, Naperville Code Enforcement Team Supervisor.

With her roof, Armstrong said she's hoping to show others that possibilities beyond the norm exist.

Why'd she do it?

"To see if it could be done," she says simply.

To construct their rooftop prairie they put numerous layers into the project, including waterproof membrane and a wooden grid system designed to contain the soil and growing plants. She used a lightweight soil mixture that drains well and resembles tiny pebbles.

Three years into its existence, her rooftop paradise is just hitting its stride.

For months in 2004, Armstrong pored through catalogs and visited nurseries selecting just the right native species and plotting them out in an elaborate landscaping design. She knew exactly where each plant was destined to grow.

It took five straight days of planting in the spring of 2005 to get nearly all of the seedlings or bare-root plants into the ground. That year was the only one that Armstrong actually ever watered her roof.

It's taken three years for the plants to fill in, covering the soil with vegetation. This year, because there's been so little rain in August, the prairie's already started going dormant well ahead of schedule. Armstrong is hoping the plants will make a full recovery.

She can tell that some of her desired varieties didn't thrive, prairie gaillardia, for instance never even made it into the second year. So 2008 is the year of taking inventory.

Armstrong's up on the roof again, climbing up the ladder that's permanently stationed against her house, taking stock of each and every plant up there. She knows how many of each species she planted and where they're supposed to be growing - now she's cataloging how many actually are left and where their progeny have spread. Or not.

As painful as it might be, she might actually have to do some thinning. Some of her choices not only are thriving, it "seems they've taken off like weeds."

And that's the one thing Armstrong absolutely will not tolerate in her yard.