Bulbs on roofs?
By Ed Snodgrass, Plant Editor
August 2, 2008

Ask Ed Q & A Column
All Photos Courtesy Ask Ed unless otherwise noted

 

As we all sweat through the dog days of summer, we should all remember that fall will be approaching sooner than we think and those beads of sweat will be giving way to cool nights and frost.
 

Fall is the time to plant bulbs, and green roofs have been largely left out of the bulb discussion.  Are bulbs part of a green roof planting plan?  Can bulbs work on thin system green roofs?  Knowing that many of our modern Tulips came from the Anatolian region of Turkey, known for its hot dry summers, I thought species Tulips may have a chance on a green roof.
 

I thought I better ask someone who knows bulbs more than I.  I spoke to both Brent and Becky to ask them what bulbs they thought could survive in an extensive green roof environment.  Well, with the help of Brent and Becky’s Bulbs, www.brentandbeckysbulbs.com, Emory Knoll Farms have been running bulb trials on our test roofs.  We planted over 30 varieties of bulbs last fall on our main test roof in 3.5 inches of non-irrigated media.
 

The following genera are represented: Crocus, Narcissus, Tulipa, Muscari, Dichelstemma, Calochortus, Iris, Scilla, Allium, Ornithogalum, Camassia, Chionodoxa, Puschkinia, and Ipheon.
 

We planted half of each variety on the roof and half in our rock garden so we could compare viability, vigor, bloom size, and other general plant characteristics.  This spring all the bulbs we planted on the roof made it through the winter and performed nicely although the foliage was somewhat smaller in size than the bulbs in the rock garden, the blooms looked about the same.
 

The real test will be how many survive the summer.  We look forward to more bulb displays next spring, but in the meantime, we encourage others to plant some bulbs this fall and see what surprises your springtime on your roof will bring.
 

Ed Snodgrass, Emory Knoll Farms/Green Roof Plants
 

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8.03.08
Dear Ask Ed,

I'm trialling two irises, Iris cristata and Iris pumila 'Boo' at the Rock Mill Park trial models in Alpharetta, GA.  They're both doing OK but their leaves burned a bit recently during some 98° summer days.  A local nurseryman suggested that we try trialling daylilies, too, as he thinks they'll perform well in our extreme Atlanta heat.  What do you think about daylilies on roofs?

Linda V. in Hotlanta

Dear Linda V.,

There is a daylily roof in Toronto, not doing very well at all.  I don’t know that it's all the daylilys' fault or not.  But in any case, the plants are shrinking every year and headed to oblivion.
 

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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

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