Greenroofs.com: Do You Speak "Green Roofs" with an Accent? By Ed Snodgrass

Do You Speak "Green Roofs" with an Accent?

By Ed Snodgrass, Plant Editor
Ask Ed Q & A Column
All Photos Courtesy Ask Ed unless otherwise noted
July 26, 2010

In cooking, isn’t it amazing what just a small amount of the right spice can do for the taste of a dish? I feel the same is true for a green roof. If the right accents are used, you can dramatically increase the aesthetics and diversity of a green roof while not affecting the cost or reliability. With that in mind, I want to share some of my favorite "accent" plants.

The Emory Knoll Farms Test Greenroof

Phemeranthus calycinus, syn. Talinum calycinum

Known as Talinum in the trade, this species is one of 17 species native to the continental U.S. It is a great plant supplying pollen and nectar for pollinators and blooming every afternoon all summer. Pink to purple five petalled flowers stand atop long wiry stems. This allows them in many cases to be seen by folk not on the green roof. By the first frost, the foliage disappears and only a carrot like small root remains. It does produce viable seed and prefers to germinate in open soil.

Phemeranthus calycinus, syn. Talinum calycinum

Campanula rotundifolia

Campanula rotundifolia is a widespread American wildflower that ranges from Canada to the Gulf of Mexico. Because of its wide distribution it is a food source for many insects. It has an early summer bloom of a pale blue bell shaped flower. It may perish in periods of drought but it is worth a replanting.

Campanula rotundifolia

Aster alpinus

Aster alpinus is a stunning flower in spring with purple petals and a yellow center with dark green foliage. It is a mountain wildflower and very hardy. There is a darker petal form called Aster alpinus Dunkle Schone and also a white flowering variety Aster alpinus ‘Alba.’

Aster alpinus

Delosperma ‘Lavender Ice’

Delospermas have proven to be a very nice green roof plant. They are drought tolerant groundcovers with few exceptions. They tend to be very floriferous and have long bloom cycles. Delosperma cooperi and Delosperma nubigenum have been the most reliable performers on green roofs but this one is worth a look just introduced from the Plant Select folks in Colorado.

Delosperma ‘Lavender Ice’

Phacelia campanularia

A desert species from the southwestern U.S. also called California bluebells, this plant works well on green roofs as a food source for bees and other pollinators. It will recede as the green roof fills in as it needs open soil to germinate. It is an annual and will reseed some but you may need to refresh every few years with new seed. It can be planted with plugs or sown directly. It will need a cold period to germinate from seed.

Phacelia campanularia

Sedum pulchellum

Sedum pulchellum is a south eastern native that is a biennial but will act like an annual on a green roof. It can be planted as plugs or sown directly from seed. It has showy pink arching flowers in spring. Unlike most eastern native sedums, it is fairly well suited to the conditions on a green roof.

Sedum pulchellum

Opuntia aurea

This prickly pear is a pink flowering species with great red winter color. It is slower growing and doesn’t lay flat like Opuntia humifusa, but I think it is worth the effort. You may want to invest in a pair of long needle nose pliers for weeding.

Opuntia aurea

Doreanthus bellidiformis

Also called Livingston Daisies, Doreanthus bellidiformis is a wonderful South African annual that blooms in a wide range of colors. Best if sown directly on the roof late fall or early spring. It can be very useful early in a green roof’s life providing color and occupying space while other more perennial species are growing in.

Doreanthus bellidiformis

In the design world, just like selecting the choicest herbs for the right sprinkling of seasoning, or speaking a new language with just the right manner of pronunciation, careful selection of green roof accent plants will ensure just the right contrasting detail or decorative feature to add flair to your roofscape.

Dansko Corporate Headquarters; Photo Source: Horticulture by Heart

So if you want to add some visual interest to your green roof or increase the biodiversity, try speaking with an accent.

Dansko Corporate Headquarters, West Grove, Pennsylvania

Ed Snodgrass, Emory Knoll Farms/Green Roof Plants

Send your questions or comments to: PlantEditor@greenroofs.com or phone Ed at: 410.452.5880. Visit Emory Knoll Farm's website: www.greenroofplants.com

Publisher's Note: Follow Ed as he travels to present about greenroofs - here's his Speaking Schedule for the next seven months:

Tuesday, August 03, 2010: Pittsburgh, PA; ESA Annual Meeting, Ecological Society of America

Wednesday, September 15, 2010: London, UK; World Green Roof Congress, CIRIA and Livingroofs.org

Thursday, September 30, 2010: Washington D.C.; Green Roof Seminar, US Botanic Garden

Thursday, October 21, 2010: Adelaide, Australia; Australian Green Roof Conference, Green Roofs Australia

Thursday, November 11, 2010: Swarthmore, PA; APLD Conference, Association of Professional Landscape Designers

Wednesday, December 01, 2010: Vancouver, BC; Cities Alive, Green Roofs For Healthy Cities

Tuesday, January 11, 2011: Kennett Square, PA; Six-Week Longwood Plant ID Class, Longwood Gardens

Tuesday, January 18, 2011: Kennett Square, PA; Longwood Plant ID Class, Longwood Gardens

Tuesday, January 25, 2011: Kennett Square, PA; Longwood Plant ID Class, Longwood Gardens

Tuesday, February 01, 2011: Kennett Square, PA; Longwood Plant ID Class, Longwood Gardens

Tuesday, February 08, 2011: Kennett Square, PA; Longwood Plant ID Class, Longwood Gardens

Tuesday, February 15, 2011: Kennett Square, PA; Longwood Plant ID Class, Longwood Gardens

Wednesday, February 16, 2011: Doylestown, PA; Founders Lecture, Delaware Valley College

Friday, February 18, 2011: Las Vegas, NV; International Roofing Expo, IRE

Tuesday, February 22, 2011: Kennett Square, PA; Longwood Plant ID Class, Longwood Gardens

Learn more about Ed and read Past Ask Ed Articles.

The opinions expressed by our Guest Feature writers and editors may not necessarily reflect the beliefs of Greenroofs.com, and are offered to our readers to simply present individual views and experiences and open a dialogue of further discussion, debate and research. Enjoy, and if you have a particular comment, please contact the author or send us an email to: comments@greenroofs.com.

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