Overview

• Adding coffee grounds to hydrangea soil increases acidity to shift pink and purple blooms toward blue hues.
• This color-changing effect applies exclusively to Bigleaf (Hydrangea macrophylla) varieties, and white hydrangeas remain unchanged.
• Used coffee grounds enrich soil with nitrogen, phosphorus and potassium to promote stem, leaf and root development.
• The caffeine content in grounds acts as a natural slug deterrent and helps the soil hold water between watering sessions.
• For best results, gardeners should apply about one cup of coffee grounds per plant each month and monitor soil pH, as full color transformation may take up to a year.