Ericaceous Compost: Make Acidic Compost for Rhododendrons, Blueberries & More

"Ericaceous" refers to acid-loving plants in the Ericaceae family—rhododendrons, azaleas, blueberries, camellias, pieris, heathers, and many more. They need soil pH 4.5–6.0. Standard compost drifts neutral; ericaceous compost stays acidic.

Plants That Need Ericaceous Compost

Rhododendron, camellia, cranberry, blueberry, azalea, gardenia, pieris, hydrangea, viburnum, magnolia, bleeding heart, holly, lupine, juniper, pachysandra, fern, aster, Japanese maple.

How to Make Acidic Compost

Follow standard layering but omit lime (which raises pH). Boost acidity with:

• Oak leaves
• Pine needles
• Coffee grounds

Layer 6–8 inches organic matter → sprinkle acid-formulated fertilizer (1 cup/sq ft) → 1–2 inches garden soil or finished compost → repeat to 5 ft height. Water each layer.

Note: Compost eventually neutralizes. Pine needles acidify temporarily until decomposed.

Ericaceous Potting Mix Recipe

• 50% peat moss (or coir for sustainability)
• 20% perlite
• 10% compost
• 10% garden soil
• 10% sand

No true substitute for peat's acidity, but coir works for structure.