Question
I am interested in planting crowns of asparagus and strawberries here in northwest Ohio this mid May. Since both will produce for years to come if left undisturbed I want to build a raised bed utilizing rock as the retaining retaining wall approx. 12-15" high. The rock is round and anywhere from 4" to 12" and some slightly larger in diameter, all collected on the property.

I noted on a post it was mentioned that cement is not toxic to plants, however I read at other sites that using cinder blocks, bricks, cement blocks for a basis will affect the soil pH over the years.

Is this correct? I would prefer to dry-stack, but I'm leary that using the native round rock we have will not hold over the long haul without out cement mortar. I would noot want to introduce cement into the garden if it compromises the soil as I have maintained it free of chemicals now for 12 years, but certainly would use cement if it works with my gardening philosophy.
Thank you, K.

Answer
I don't think there is any problem with using cement.  We use a mixture of Portland cement (chemically it is a mixture of (Dicalcic and Tricalcic Silicate, Tricalcium Aluminate, limestone, shale, and gypsum), mixed with a cement sand in a three to one ratio.

The only effect we have noticed over 16 years is that along the edges, water is absorbed, and the soil is not as moist as it is in the center of the bed. In the testing of our soil for organic certification, nothing was found to be contaiminated in any way.

You could use Natural cement: which has only Dicalcic Silicate (Belite). It is produced from argillaceous limestone and called Rosendale Natural Cement, available from Edison Coatings, Inc. at 3 Northwest Drive, Plainville, CT 06062, Phone: (860) 747-2220 or (800) 697-8055
http://www.rosendalecement.net/html/rosendale_cement_chemistry.html

You could also dry stack with just a little cement inbetween the rocks making sure that the soil side had as little as possible.  This would work if your rocks were flat. This would stabilize the wall with as little cement as possible in contact with the soil.

If you are concerned about the pH of the soil, test it every spring and if it is not where you need it to be for asparagus and strawberries, add some soil ammendments.  

For more information on soil building visit our website: http://www.avant-gardening.com