To bring up the heights of the north and south waves, only styrofoam was used to keep the weight down. This was formed into a stairstep layer along with the various layers of the green roof and covered.

The south wave, with 4.5 inches of growing media, had the most dramatic change over the years with the disapperance of the phlox and (Silene caroliniana).

Due to the weight constraints on the roof, the south wave is only five feet high. The HVAC system was placed several feet away from the green roof infrastructure so as to not add additional weight.

The south wave's original plants have been replaced mostly by the spreading of (Sedum kamtschaticum), which has yellow blooming flowers and broad leaves, and have done exceptionally well on the roof.

The aluminum grating has proven to be a great asset on the green roof. It not only provides a wonderful walking surface, as opposed to flagstones, it provides shading for the sedum, thus water retention. Coverage is at 100 percent below the grate.

The Prickly Pear cactus (Opuntia humifusa) has grown so well, it has been cut back and intermingled onto the back of the wave with the additional sedum. Over time, the south wave will most likely be only sedum and cactus.

The green roof has proven to be a great urban environment for pollinators as seen here with the bee in the cactus.

The staircase, which has 12 inches of growing media and was incorporated into the public demonstration project, has had abundant growth with the fragrant sumacs (Rhus aromatica). The staircase accounted for two-thirds of the cost of the green roof project. The staircase and elevator shaft, which is covered with 21 inches of growing media, are the only intensive portions of the green roof with the drip irrigation system.

Watch a 1.5-minute video of the ASLA green roof that not only promotes its beauty and wildlife, but also pollinators in an urban setting.

Due to the robust growth of the fragrant sumacs (Rhus aromatica) over the new staircase, all the other initial plants, such as the New Jersey tea (Ceonanthus americanus), sweet fern (Comptonia peregrine), and Pasture roses (Rosa carolina) have been sacrificed. The fragrant sumacs are bursting at the seams and make for a great wildlife habitat in an urban environment.

The flame sumacs (Rhus copollina) have done quiet well, again, accounting for the drip irrigation system that was installed on the intensive portion of the green roof (intensive green roofs have growing media depths above six inches). The flame sumacs also contributed to the 59-degree cooling difference from a black roof in the neighborhood; numbers that increased significantly from a 32-degree difference after the trees matured.

The initial plantings on the elevator shaft, which has 21 inches of growing media, were the trumpet vine (Campsis radicans) and flame sumacs (Rhus copollina). The trumpet vine has still not covered the trellis, which would allow for additional shading. Reasons: drip irrigation must be on at the beginning and throughout the growing season; it grows better once it attaches itself to the wall and is not "forced around" to the trellis; the most current vine is up the wall and in with the trees. After a few years, it was noticed that the flame sumacs were sapping the water from the trumpet vine so a root barrier was installed to divide the two species of plants.

This axiomatic drawing shows the layers of the green roof.

The (Allium schoenoprasum) was a welcomed surprise after taking a few years to show up but offer great color to the green roof early in the spring season now that the pholx and (Silene caroliniana) have all but disappeared on the south wave. Note the very small sprinkler that remains on the north side. This has been removed from the south wave, which mostly is now sedum and cactus.

The north wave, with its six inches of growing media, has an abundance of grasses and other plants. From the initial planning, it is now covered with about 50 percent sedum, most notably, (Sedum kamtschaticum). This thick, broadleaf plant has done so well, as it has on the south wave, that has even curtailed the growth of Hare's foot clover (Trifolium arvense).

The green roof is now completely covered, and plants are not accepted from outside sources any longer. Some plants are taken from other areas of the green roof to fill bare spots. Many areas have abundant sedum hanging over the sides. Note the Hares-foot clover (Trifolium arvense) in pink that invaded the roof through airborne seeds.

Many of the Thread-leaf tickseeds (Antemis tinctoria) still exist with their yellow blooms and are a favorite of the pollinators.

The butterfly milkweed (Asclepsia tuberosa), which is important for pollinators, is not as prominent as when first planted. ASLA pulled seeds from the north wave, where the plant had done well, and planted new milkweeds on the south wave, which are also doing well.

Later in the season, after all the chives (Allium schoenoprasum) have bloomed and dropped off, the nodding onions (Allium caranuum) begin to bloom in late July. They have remained prominent on the north wave with their clusters of purplish-white flowers.

The silver king (Artemisia ludoviciana) still makes its presence each year. While not as robust as in the earlier years, it still offers great color on the north wave.

The black-eyed Susans (Rudbeckia hirta) appear sporadically each season. ASLA tied a sprinkler into the drip irrigation system to offer water during the hottest days. Even with this sprinkler system, many of the taller plants didn't survive. The sedum has also benefitted from watering—it has grown to about 50 percent coverage on the north wave.

The north side also has one small shady area that is adjacent to the elevator shaft. Many of the shade-loving plants such as the black-eyed Susans (Rudbeckia hirta) migrated there, but the Virginia wildrye (Elymus virginicus) is quite prominent there now. Plants are utilizing the extra water from the HVAC and are constantly cut back from the air intake area.