En Español

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
1 rating

Sunday - September 07, 2008

From: Knoxville, TN
Region: Southeast
Topic: Compost and Mulch, Planting, Turf, Grasses or Grass-like
Title: Submerged paving under lawn
Answered by: Barbara Medford

QUESTION:

I had 4 patches of rectangular areas (about 4'x6'or more) in my lawn where the grass is fine in spring but totally dies in summer. I decided to till these bare patches so that grass may grow better when I reseed. I was surprised to hit concrete in one spot and on digging deeper I discovered there were concrete slabs from what must have been an old pavement buried there - which explains why the grass dies in summer when the concrete heats and burns the root. The slabs seem to be huge connected long pieces - I don't think I can manually remove them. Can I re-cover the area with topsoil and have the grass grow well(even in summer)? If so, how many inches of top soil should I put on top of these concrete slabs? If not what do you suggest I do?

ANSWER:

Underground paving is a little out of our line, since the Lady Bird Johnson Wildflower Center specializes in the care and propagation of native plants. A couple questions you need to ask yourself before you make your decision are: How many square feet of lawn would you have to cover in topsoil to make it all level and the dirt over the slabs deeper? Do you grow annual grasses from seed, or do you have perennial grasses that grow by rhizomes and runners?

If you have perennial grasses that make a sod, throwing topsoil on top of that to make the depth equal with what you have to put over the slabs is just going to mean your grass roots will grow down to the sod, now underground, and probably will not prosper. If your grasses are annual, and die completely back in the winter, you could rake that, even leave the dead grasses as compost, and cover with several inches of topsoil. We say "several" because we don't know what grasses you grow or how deeply their roots are going to reach, and, therefore, we don't know how much height you need to add to the dirt over the slabs. Unless you intend to have little hillocks over the slabs, you are going to need to spread the same amount of topsoil over the entire lawn. 

Second possibility, you could pretend you planned it this way, and put raised, walled beds over the slabs, tilling up the grasses and removing them, hopefully before they seed. This website Raised Garden Beds (eartheasy) will help introduce you to the concept. You can then plant colorful flowers and quit worrying about the grass. This will require some expenditure of time and money, obtaining the materials, assembling the beds, and adding good soil and compost to the beds. 

Finally, you can do what you said you didn't want to do, and go in after those slabs. This would require some heavy equipment and hauling, and then you would still have to put more soil in there to make up for the concrete that has been removed. 

And, if you ever find out what those slabs are, let us know. We're dying of curiosity.

 

 

More Grasses or Grass-like Questions

Trimming of cordgrass plants
November 20, 2007 - We have planted more than 150 cordgrass plants (spartina bakeri) along the edges of the small pond at our condominium complex to try to prevent any further soil erosion between the buildings and the p...
view the full question and answer

Ground cover that won't hide snakes from Asheville NC
June 29, 2012 - I have an unusual situation: several bare areas in an otherwise wooded area, which receive partial sun, and are not near water -- it rains here frequently, but the soil can become quite dry at times. ...
view the full question and answer

Post freeze care for Texas native grasses
January 05, 2008 - Can you tell me the best post-freeze care for Tx native grasses in my garden: lindheimer muhly, gulf muhly, inland sea oats. Mexican feather grass. Do I cut them back? Burn them? Leave them alone? T...
view the full question and answer

Planting creeping phlox for a groundcover
June 13, 2014 - Dear Mr. Smarty Plants, I live in Southwestern PA (zip code 15065). I have a small slope on my property that is hard for me to mow. I would like to cover it with creeping phlox, which I saw on t...
view the full question and answer

What is a lawn broom from Cibolo TX
February 15, 2013 - Concerning gulf muhly grass you mention using a lawn broom to get rid of the dead stalks. What is a lawn broom? What does it look like? Where can I purchase one?
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | JOBS | SITEMAP | STAFF INTRANET
© 2016 Lady Bird Johnson Wildflower Center