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Friday - November 20, 2009

From: Wayne County, TN
Region: Southeast
Topic: Green Roofs
Title: Plants for green roofs in Wayne County TN
Answered by: Barbara Medford and Joe Marcus, Mark Simmons

QUESTION:

Are any of the plants recommended for green roofs more subject to fire during drought conditions? Our application will be on a rustic wood cabin, thus the importance of safety from fire.

ANSWER:

If you have not already read it, please see our article on Green Roofs. The Lady Bird Johnson Wildflower Center has been very active in research and development of this fairly recent technology. The lead person for that project is Dr. Mark Simmons who passed on this piece of advice.

"Although the plants are flammable, the fact that you have growing media on the roof actually can improve fire protection (this according to Austin Fire Dept). Alternatively to improve this, however, it makes sense to use a carpet of succulents - you will have to check the best species for your area." Dr. Simmons also recommended you get a copy of Green Roof Plants: A resource and planting guide. See the Bibliography below for more information.

Another staff member at the Wildflower Center, Joe Marcus, offered these observations.

"I would think that the relative fire susceptibility of green roofs would depend on four factors: the materials used to construct the roof, the growing media, the plants used on the roof and the moisture content of each of these."

"For example, if the roof is constructed of steel, has media high in clay content and is planted with succulents, then it would seem the fire potential would be very low. In fact, it would help prevent fires. On the other hand, if the roof of the cabin was constructed of flammable materials - wood and/or plastics - the media had high peat content (which is burned for heating and cooking in many parts of the world) and was planted in grasses, then it might be quite a fire hazard during times of drought. "

From these thoughts, we can draw a tentative conclusion that most green roofs are more fire retardant than more traditional roofs - especially more traditional cabin roofs. If you could, as Dr. Simmons suggests, incorporate succulents, a group of plants that contain quite a bit of moisture, that would help even more.

The problem then becomes finding succulents native to Wayne Co. TN that would thrive there. Three that we found native to Tennessee and your area:

Manfreda virginica (false aloe) More information and pictures of this plant from missouriplants.com.

Sedum ternatum (woodland stonecrop)

Sedum pulchellum (widowscross)

We suggest that you go to our Species List for Green Roofs and see what plants in that list would grow in your area. Also try this website on Succulents.

From our Native Plants Image Gallery:

Manfreda virginica

Sedum ternatum

Sedum pulchellum

Bibliography

Green Roof Plants: A Resource and Planting Guide (2006) Snodgrass, E. C. and Snodgrass, L. L.

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