Regional Gardening Reports :: National Gardening Association

In the Garden:
June, 2009
Regional Report

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When conditions are desertlike -- dry, hot, and sunny -- thick-leafed sedums are an attractive low-maintenance option.

Surprising, Sustainable Sedums

Most of us don't worry about our plants flying away under the tempest of a helicopter's whirling blades. Philadelphia's PECO headquarter's green roof with helipad isn't your typical garden. Its perennials live in extremes of wind, sun, and heat.

However, its textural, colorful, sculptural sedums -- some blooming white, others yellow or pink -- ARE within our reach for a fascinating, low maintenance, drought-tolerant landscape.

Low-growing sedums don't usually catch my floral-seeking eye. Being up close and personal with nearly 43,000 square feet of thriving showy stonecrop (sedum's common name) gives pause -- and appreciative perspective. En masse, this mingling array of ten sedum varieties is quite beautiful. It's easy to imagine the mix bordering a path, walkway, driveway, or forming a rock garden, or covering a sunny, dry slope.

On a recent June afternoon, The Pennsylvania Horticultural Society hosted a trolley tour featuring PECO's green roof at 23rd and Market along with other Philadelphia Green projects.

Last fall, the stonecrops were planted on the green roof as vegetative mats in 4 inches of gravel and some compost. Newly installed young ornamental grasses and flowers in raised beds haven't yet filled out. Retrofitting this roof portion, which covers mechanical equipment, is one step in Leadership in Energy and Environmental Design (LEED) green building certification.

From a sustainable, environmental view, green roofs are built primarily to control storm water runoff. The PECO green roof is designed to absorb 60 to 70 percent of approximately 1.5 million gallons of annual rainwater falling on the main office building.

Green roofs can significantly reduce roof temperatures which can lower building heating and cooling costs. Green roof plants absorb air pollutants.

Pink, Red, Rose Foliage/Flowers
This non-irrigated sedum tapestry includes low green and red swirls of Sedum album 'Coral Carpet'. The foliage turns red under stress, and in drought and cold. Its parent Sedum album is a taller (6-inch) green roof staple with white flowers and green leaves that turn red in winter.

Short, blue-green Sedum hispanicum shows blues, pinks, and purples depending on temperature, water, and nutrients.

Sedum spurium 'Rosea' leaves form circular florets; they bloom pink in autumn. Sedum spurium 'Fuldaglut' (two row stonecrop) forms mats of thick, oval, maroon leaves on four-inch stems with small, rose-red, star-shaped flowers in August.

Yellow Flowers
Yellow-flowering Sedum kamschaticum is 6 inches tall and resembles pachysandra from a distance. Eight-inch Sedum rupestre holds bright yellow flowers high above blue-green leaves and stems. Clumps of 8-inch green Sedum sexangulare have yellow blooms too. Sedum floriferum spreads lushly to 12 inches with canary yellow, star-shaped flowers in spring. Light green Sedum hybridum 'Immergrunchen' turns amber in winter and blooms yellow in June and September.

Many green-roof recommended sedums hail from the tough environment of the Ural Mountains to Mongolia. They're long-lived. They self-propagate. When they reach mature height on the roof, they're gently cut back. The cut stems are tossed on empty or sparsely populated spots, then watered so they'll take root.

In case you're just curious OR your helicopter's coming in for a landing on your sedum garden: Spraying the sedum and gravel with water keep all in place through the whirlwind.

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