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I am getting ready to upgrade my aging and rotting wooden raised beds to ones made from 8x8x16 hollow concrete block (Concrete Masonry Units). As I understand it, the lime in the concrete can leach out over time and increase the soil pH, making it very alkaline. Blueberries are acid-loving plants and require quite acidic soil.

If I have a raised bed that is 4 feet wide, and 2 feet deep, and I plant a row of blueberries down the center of the bed, will they be negatively affected by the rising pH of the soil near the concrete blocks?

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Yes and kudos to you cathode!! But...you can change the pH and have to test and stay on top of the sulfur applications, yes you can lower the pH. Even beside concrete and masonry. I am impressed you knew to bring this up!

Also, what side of the home are these blueberries? How old are they?

They love almost TOO much water, a cooler side of the home such as the north or east side.

I would like to convince you to think about raised beds without concrete, I always have raised beds with no wood, no concrete for all kinds of soil.my raised beds[![][1]]2

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  • I would much prefer to do raised beds without walls, but I am in a tight urban lot and I'm trying to make do with the space I have. I'm also gardening in my front yard so I'm attempting to maintain a neat/landscaped appearance to avoid complaints and increase curb appeal for the house. I will look into alternatives for the blueberry bed. – cathode Apr 10 '17 at 16:49
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Standard recommendation for 50 years or more (I have old books) has been to line concrete beds that will be used for acid-loving plants. In days of yore that would have been tar/asphalt type material - these days EDPM rubber (also known as pond liner, also known as rubber roofing) is a somewhat friendlier approach with very long life.

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  • I have a roll of a product called 'Dura-Skrim" that is a 20-mil polyethylene sheet made of two 10-mil polyethylene layers bonded together with a woven polyester netting sandwiched between. It's FDA rated for food contact and NSF approved for potable water systems. It also has UV stabilizers. Can I assume that this would be an acceptable product to line the concrete with? – cathode Apr 10 '17 at 20:54
  • Seems like it should work, yes. – Ecnerwal Apr 10 '17 at 22:24
  • Yes, it will work but just cover the concrete so that it isn't leaching lime constantly. I have to add don't use this rubber pond liner beneath the bed. You will still have to be vigilant on pH and keep checking every year until you get tests that show the change over time...your soil already is full of lime so that has to be dealt with. Covering that concrete with a liner (or check out spray on Rhino LIner...or ask a Rhino liner company....this Rhino liner is amazing and completely negates pond liner in lots of circumstances. Does your foundation have asphalt emulsion coat below soil? – stormy Apr 11 '17 at 0:09

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