En Espa—ol

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
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
Not Yet Rated

Monday - May 11, 2009

From: Kyle, TX
Region: Southwest
Topic: Rain Gardens
Title: Expanding clay soils near rain garden
Answered by: Nan Hampton and Chris Caran

QUESTION:

I want to put a rain garden in my yard in central TX (Kyle). My subdivision architectural review committee expressed concerns about the expansive clay soils becoming saturated and possibly shortening the anticipated lifespan of a sidewalk and alleyway near by. How do I find information about setback distances for clay soils? I have found that most rain garden plans recommend 10' from foundations, but no comment or mention about distances form sidewalks and alleyways. I found that in Seattle they have rain gardens in the planting strip between the roadway and sidewalk without concern for damage to road or sidewalk. How or where can I get help with this concern? Thanks

ANSWER:

First of all, and I'm sure you know this, Seattle soils are not like Kyle soils.  I've thought about your question a great deal and, although I wasn't able to find any exact recommendations for distances from sidewalks or streets,  I did get some insights from consulting a geologist friend who knows a lot about the expansive clay soils of Central Texas.  This is a summary of what he says about your problem:  When the weather has been dry, these expansive clay soils shrink and become permeable with small channels running through them much like the honeycomb limestone of the area.  When it rains, the water runs through them vertically until they absorb enough to expand and become impermeable.  They expand vertically as well as horizontally.  When they absorb enough water to become impermeable, the water runs off the surface.   The soil can't expand further at this point.  The water you catch in your rain garden pond is going to permeate the clay soils underneath it until they become saturated and almost impermeable.  Then, the pond will hold the water until it evaporates or seeps slowly down into the ground.  The soils under and perhaps adjacent to the rain garden WILL expand considerably once they are wet, so any structures (e.g., pipelines, walkways, etc.) in the immediate proximity of the garden can be expected to shift.  The adjoining clay soil in the yard is also going to expand just from the rain that falls on it and the soils near the sidewalk will expand after a rain regardless of whether there is a rain garden nearby or not.  If 10' is the recommendation for foundations, that would seem an adequate distance for sidewalks as well.
 

More Rain Gardens Questions

Raingarden Plants for Brownsville, TX
March 14, 2014 - I'm a Landscape Architect in South Texas and I'm implementing raingardens and vegetated swales in my projects. What native plants could be used in these gardens/water runways. They would need to res...
view the full question and answer

Native plants for rain garden in Collin Co., TX
November 09, 2006 - I am developing a Collin County Master Gardenerís program on Rain Gardens (in particular) and Rain Harvesting (generally.) I saw the recent article in your magazine about rain gardens and wondered if ...
view the full question and answer

Native plants for a bioswale in Indianapolis
March 07, 2009 - Dear Mr. Smarty Plants, Can you please recommend the types of plants I should use in a bioswale or rain garden in Indiana?
view the full question and answer

What plants can absorb the excess water in my back yard?
February 20, 2009 - I am looking for any plants and trees that can absorb the excess water in my back yard. There is a large area that is swampy and always wet. Could you please provide me some suggestions?
view the full question and answer

Plants for a bioswale in New York City
August 03, 2010 - I am interested in learning about the best vegetation for planting in a bioswale in New York City. Can you help? Thanks!
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center