Rock Retaining Walls for Raised Beds: Dry-Stack vs. Mortar, pH, and Longevity

Building 12–15" raised beds with native round rock (4–12") for asparagus and strawberries. Cement vs. dry-stack: the facts.

Cement (Portland) Is Safe

• Composition: dicalcium/tricalcium silicate, tricalcium aluminate, limestone, shale, gypsum.
• 16-year organic certification testing: zero contamination.
• Only effect: edges dry faster (water wicks into mortar).

Natural Cement Alternative

• Rosendale Natural Cement (dicalcium silicate only).
• Source: Edison Coatings, Plainville, CT — rosendalecement.net.

Dry-Stack Options

• Round rock is hard to stack stably without mortar.
• Compromise: dry-stack with minimal mortar between rocks on back (soil) side only.
• Or: plywood forms, rock face front, pour cement rubble core, cap with rock.

pH Management

• Test annually.
• Asparagus likes 6.5–7.5; strawberries 5.5–6.5.
• Amend as needed (sulfur for acid, lime for alkaline).

Recommendation

For round rock: use forms + cement core for stability. Or source flat stone for true dry-stack. Cement is not the enemy—poor drainage is.