Rent Shop Volunteer Join

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
See a list of all Smarty Plants questions

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
2 ratings

Sunday - November 23, 2008

From: Houston, TX
Region: Southwest
Topic: Soils, Green Roofs
Title: Soil mixes for green roofs
Answered by: Nan Hampton

QUESTION:

We are trying to set up a green roof system on our own. What do you suggest for soil? It seems the soils are proprietary and unavailable to individuals.

ANSWER:

Mark Simmons, Ecologist at the Lady Bird Wildflower Center, suggests the following recipe:  50% expanded clay, shale, or perlite; 30% decomposed granite; and 20% rice husks or another fine, slowly-degradable organic matter.  There are other mixtures that also work. For the Seattle City Hall green roof the "Roof Garden Soil Mix was: "55% PermaTill 5/16" Expanded Slate or equal, 30% USGA Root Zone Sand, and 15% Approved Compost."  Greenroofs.com suggests a mix of "1/3 clean topsoil, 1/3 compost, and 1/3 perlite or other inorganic material"  for an economical option, but this has the potential for being heavier than some other mixes.  

If you visit the Greenroofs.com directory page and choose the category "Suppliers>Individual Components>Growth Media", you will find a list of companies that sell soil mixes for green roofs.  I checked one, ERTH Products, that advertised "ERTH-HydRock Lightweight Structural Soil" described as "an engineered soil designed to be lightweight for use on structural conditions such as roof top gardens." Another company, Permatill, offers "Green Roof Planting Media".  There are more companies listed under the "Growth Media" category.  Also, you can find more information about green roof soils by Googling "green roof soil".

 

More Soils Questions

Ecosysystem with pecan at center from Austin
February 21, 2014 - Dear Mr. Smarty Plants, I would like to create a native tree guild around a mature pecan. It shares its space with native shrubs and ephemerals but I would like to add a nitrogen fixing plant. I am...
view the full question and answer

Flowers for sunny and shady gardens in Cedar Hill TX
March 30, 2010 - Last year I spent way too much on flowers for my sunny and shady flower beds. They all died from the heat, even after constant watering. What flowers could I plant in sunny and shady flower beds that ...
view the full question and answer

Baby mountain laurels are ready to move, in Lockhart Texas
October 19, 2011 - I want to harvest the baby mountain laurel plants which are growing under a large bush. What height would be best for the young plants survival? Please recommend a soil mixture for the pots.
view the full question and answer

Plants resistant to salt spray in FL
December 18, 2011 - What type of plants can I put in a small planter bed next to a waterfall with a saltwater pool? Everything I put in there dies. I live in Southwest Florida.
view the full question and answer

Is cement leaching into flower beds in Colorado Springs?
May 16, 2009 - I have posed this question to a number of garden centers in our area around Colorado Springs--only to rec. a repeated--"Gee, I don't know." When we moved to our new home there was a rock concrete ...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.