Building a Garden in the Sky

 
As the Urban Forestry intern, I recently had the opportunity to see the construction of the green roof atop the 11 story parking deck at the Cira Center South in Philadelphia. Jason Lubar, a Morris Arboretum Urban Forestry Consultant, was asked by the project’s green roof designer Roofmeadow, to assess the support systems for the planted trees.  As the green roof is 11 stories up, the wind dynamics are more intense than at street level, and the trees need a flexible, but sturdy support system to properly establish.

Green roofs have come a long way, and are no longer just moss and sedums. Roofmeadow created a beautiful design at Cira that includes:

• A grassy lawn with a small hill  
• A meadow with tall grass such as prairie dropseed, reed grass, big bluestem and perennials such as liatris, veronica, pinks, beards tongue and alliums
• Several trees including honey locusts, swamp white oaks and redbuds
• Walkways and plaza of permeable paving
• A rainwater storage system that will direct rainwater into the lawns and gardens and will mitigate the first couple of inches of rain.

The project will be completed soon, and will provide a beautiful garden and event space for the tenants of the adjacent 40 and 50-storied towers to visit and view from above.   Along with the aesthetic benefits, the garden will increase biodiversity, remove pollutants and mitigate stormwater discharge.  The green roof garden is a wonderful example of Philadelphia’s green infrastructure.

Article contributed by Trish Kemper, the Martha S. Miller Urban Forestry Intern

Green Roof Springs to Life

Photo: Louise Clarke

With winter's snow at last melted, it is time to cut back grasses and other  foliage on the Arboretum's intensive green roof at Bloomfield Farm. Pictured is Anna Bower, the Hay Honey Farm Natural Lands intern, using a Japanese rice sickle to trim last year's little bluestem (Schizachyrium scoparium) prior to new growth.  The rice sickle is a lightweight, ultra sharp tool with a curved stainless steel blade ideal for cutting thin, brittle grass stems. As the sickle is not suited to dense, woody material, pruning shears are used to cut back other plants such as Russian Sage (Perovskia atriplicifolia), Butterfly weed (Asclepias tuberosa), and Yarrow (Achillea millifolium).
With full sun and a southern exposure, it won't be long before the green roof sports new spring growth.

A good time to see the eco-roof is during the annual plant sale in May, click here for details.

Author: Louise Clarke, Bloomfield Farm Section Leader

Up On the Roof

Autumn is the loveliest season on the intensive green roof, in the aerial gardener's opinion. The grasses have matured, displaying seed heads that dance in the slightest breeze, held high above tawny foliage. Rhus aromatica 'Gro-Low' glows crimson and copper, igniting the roof with fiery splashes. Keen eyed observers may spot standard dwarf iris cultivars blooming, such as citrine 'Prince Pele'. Spiky yuccas sport yellow and green striped foliage, striking a pose even after their September blooms have faded.

Bloomfield Farm Day presents a rare opportunity for the public to view the green roof. Free with admission, the roof will be the backdrop to this fun-filled day celebrating agricultural history, including demonstrations, animals, and live music. The Horticulture Center and historic Springfield Mills will also be open for tours. Find out more on our website.

Article by Louise Clarke, aerial gardener.
Photos by Louise Clarke (top) and Rebekah Armstrong (bottom).

Up On the Roof

Louise Clarke, Aerial Gardener

Tradescantia ohiensis

Ohio spiderwort is an eastern North American perennial that blooms from May through July on the arboretum’s intensive green roof. Remembering this as a shady resident of my mother’s garden, I was skeptical of its performance on a green roof.

Spiderwort has adapted to the roof’s sunny, hot and dry growing conditions with aplomb. Its three-petaled blue flowers last only one day, like miniature daylilies. It receives no special care, other than being cut back in mid-summer after its blooms are spent. With adequate moisture, it may provide a second flush of flowers for fall. In garden beds Tradescantia may grow to 3’, but its stature is reduced on the green roof due to less moisture and leaner soil.

Up On the Roof

Louise Clarke, Aerial Gardener
If you visited the Arboretum during Bloomfield Farm Day, perhaps you noticed these cheery yellow flowers along the lower edge of the intensive green roof.

The eastern prickly pear, Opuntia humifusa, or devil’s tongue, is a native cactus of eastern North America. The green stems are flattened into pads armed with fine spines that easily dislodge, having an affinity for passing ankles. Last year’s edible red fruits persist through spring where they contrast with this year’s lemon blooms. Requiring full sun and a well drained location, the prickly pear was planted on the lower edge of the roof to spare the horticulturists a sharp surprise when performing maintenance.