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New 60 concrete box needs sealant to prevent alkaline leeching

Posted by alyceusvi Z10/11St.JohnUS (My Page) on
Tue, Mar 6, 12 at 15:17

Dear experienced hydrangea enthusiasts please share your advice.I have been waiting for years to have hydrangeas in abundance again.
We just had our patio and outdoor living room slabs poured.
We added a 60 foot long x 30 inch high and 24 inch deep planter constructed in front of a wall of huge boulders.
The base of the planter is soil and our underground utilities run under the soil.I have been successful growing mopheads in 20 " diameter pots for the last five years and controlling bloom and color. The lime in the new concrete
face wall will completely alter the ph of the soil.
What could I use to seal the interior surface of the planter before it is planted? Would a styrofoam insulation
spacer be enough? Once the planter box is filled with soil there will be no way to empty it. I can only amend it from the surface.I want to keep my hydrangeas blue.
Thanks for your suggestions.

Follow-Up Postings:

RE: New 60 concrete box needs sealant to prevent alkaline leechin

  • Posted by morz8 Z8 Wa coast (My Page) on
    Wed, Mar 7, 12 at 11:09

The suggestion for curing new concrete to ready it for plants or pond plants is to flush with water 3 - 5 times a day with the hose for two weeks. Then allow to thoroughly dry and apply two coats of concrete sealer inside, allowing to dry over night between coats. Some will suggest a third step in between flushing and sealing: Mix up a solution of 1 quart of ordinary kitchen vinegar and 10 quarts of water. (you may need more with the length of your planter)
With a stiff brush (or old broom) and generous sloshings of the solution, scrub vigorously over every square inch of the vessels inside surface. "The surfaces may bubble up a bit as the vinegar works on the free lime, but don't worry, it will not weaken the concrete."
Rinse well, allow to dry, then apply the concrete sealer.

RE: New 60 concrete box needs sealant to prevent alkaline leechin

I have heard of people who apply a coat of rubber paint (but not to grow hydrangeas!) to some surfaces. Can you research that product to see if it would help in this case too?

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