Used Coffee Grounds: Earthworm Candy, Not Just Acid for Blueberries

You've heard coffee grounds acidify soil for blueberries and hydrangeas. Reality check: used grounds are near-neutral (pH ~6.7). The acid leaches out in brewing. But they're still garden gold — for a different reason.

Why Coffee Grounds Work

• Earthworms love them — they pull grounds deep, aerating soil and casting nutrient-rich vermicompost.
• Slow-release nutrients — N, P, K, micronutrients in microbial-friendly form.
• Slug barrier — dry grounds deter slugs and snails.
• Free! — Starbucks and cafes give them away by the bucket.

How to Use

• Add to compost pile (browns + greens balance).
• Thin layer as mulch around plants (avoid thick mats that repel water).
• Mix into potting soil or worm bins.

Don't Obsess Over pH

For blueberries, elemental sulfur lowers pH reliably. Coffee grounds help soil biology — which matters more than a tenth of a pH point.