In NoMa’s Constitution Square, innovative street wells. (Parker Rodriguez)
Gardening columnist

Between Union Station and a block or two north of the crossroads of Florida and New York avenues lies an area known as NoMa ,as in “north of Massachusetts Avenue.” By any measure of urban renewal, the neighborhood seems a rollicking success.

From a wasteland of empty lots and rundown buildings has sprung whole blocks of plush apartments, hotel suites, offices and bistros. The glam high-rises have drawn a dream demographic for the developers — hip, urbane professionals who find gridlock not in their cars (they don’t have any) but in the foyer of the District’s largest Harris Teeter, with their baby strollers.

The level of construction and amenity would surely please civic leaders at the best of times; that this revival has occurred in the midst of a deep global recession makes it pretty remarkable. What is also worth noting is that the development that spurred this, the headquarters of the Bureau of Alcohol, Tobacco, Firearms and Explosives, is a strange concrete melange with all the outward charm of a Cold War military installation. Happily, its gloom is contained, for across N Street NE lies another key development called Constitution Square that signifies the ambition and urban vitality of the area.

This block alone contains 1 million square feet of office and retail space, a 200-room hotel and 440 swanky apartments, with more on the way.

The complex has a contemporary ecological polish — you can check out the Earth-friendly streetscape in the new online guide to green spaces in Washington assembled by the American Society of Landscape Architects, but it is not until you see it yourself that you get a complete sense of its features.

Trini Rodriguez and Dennis Carmichael, whose Alexandria firm, Parker Rodriguez, designed the landscape architecture, agreed to show me how it came together.

Until fairly recently, street trees were planted in impossibly small soil boxes. The roots had inadequate space to grow, the soil became compacted and these forlorn plants had to endure flood, drought, poor nutrition and heat stress. They were lucky to live 10 years.

Here, on the 1200 block of First Street NE, native canopy trees are planted in interlocking subterranean boxes called Silva Cells. These crate-like structures support the street while creating volumes of open soil for roots to wander. “There used to be another technique of using a structural soil,” Carmichael said, “but that fell out of favor because 80 percent of the volume was rock, not soil.” The cells “are expensive but they’re worth it,” he said, “for the health and longevity of the trees.”

A few feet away, the broad sidewalk is defined by a sunken bed planted with amelanchier trees and rushes, which rise out of a gravel mulch. The bed is framed by a raised curb whose gaps receive rainwater from the sidewalk. The planted well also traps hundreds of gallons of storm water from the street and stores and filters it. Some of it percolates into the soil, some evaporates, some is returned — but not before it takes some of the pressure off the District’s combined storm sewers.

The landscape architects also designed a series of elevated courtyards and terraces within Constitution Square for the office workers, hotel guests and residents. Some of the spaces are more expansive and passive than others, but they bear witness to the need of city dwellers to connect to nature and the environment. Within these interior yards, you can walk your dog, have a barbecue or sit and take in the Washington skyline. Some spaces are more intimate than others. A central courtyard features a large water feature of blocks, basins and water channels that looks like a cubist’s take on a European town square fountain. “This is like a plaza,” said Rodriguez, a native of Spain.

Running through the courtyards is a geometric treatment of the various surfaces — grass, decking, pavement, plant beds — as well as the recurring motif of black granite seat walls that lend a visual rhythm. “One of the signatures of all these courtyards is that close up you see rich detail, and yet it’s a very simple design pattern, so if you are 10 floors up looking down, it has a strong graphic quality,” Carmichael said.

Our last stop is the top of the building, where the designers installed a green roof and a swimming pool terrace. Green roofs, like the street wells, are designed to trap a measure of rainwater in the granular soil mix that extends four inches or a bit more. It’s a harsh environment for plants, and the palette is limited to hardy, heat-loving things such as sedums. In addition to retaining rainwater, the roofs cool the building below and, yes, they can look beautiful, especially when the ground covers of little fleshy perennials turn red and purple in the fall and winter.

As we look out to surrounding buildings, we see a city in transition. The rail yards of Union Station resemble a child’s train set. A parking lot is covered in black, heat-grabbing asphalt, but the roofs of the new buildings have gardens or light surfaces, which reflect sunlight. The idea is that as city roofs become greener and lighter, as the canopy of trees is expanded, the heat island effect is reduced.

This ecological sensibility is now uppermost in the work of landscape architects. “When we were at school,” Carmichael said, gesturing to his colleague, “It was called stewardship. What’s interesting is that the broader public is now putting a high value on it. We are seeing that climate change is real, and we are going to have to start designing our environment to mitigate that.”

Later, Carmichael told me that “one of the other messages is that landscape isn’t just on the ground anymore. When real estate becomes premium, every surface has a role.”

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Read past columns by Higgins.