Are coffee grounds beneficial for rosemary?
Written by
Michael Sullivan
Reviewed by
Prof. Charles Hartman, Ph.D.When using coffee grounds for rosemary, you must be cautious of the benefits versus the risks. Coffee grounds will slowly increase soil acidity and contribute a minimal amount of nitrogen. Still, they tend to promote fungal growth, which can lead to possible compaction problems. Most gardeners would rather find another option to maintain the health of these Mediterranean herbs without sacrificing drainage.
Potential Benefits
- Slight soil acidification (pH 6.0-6.5 ideal)
- Minimal nitrogen content (0.5-2% by weight)
- May deter slugs and snails temporarily
Documented Risks
- Promotes fungal growth when used fresh
- Compacts soil reducing essential aeration
- Attracts mold gnats in container plants
Safe Application
- Compost thoroughly before using
- Limit to 10% of total soil volume
- Always mix with coarse drainage materials
I have experimented with coffee grounds on rosemary for 2 seasons. The results were less growth than with compost tea. The coffee grounds created dense mats to repel water, which I was trying to mix in. After that experience, I am convinced that rosemary prefers open, gritty soil without dense organic matter, such as coffee grounds.
For best results, use drainage amendments, including coarse sand or perlite. Add thirty percent drainage amendments to any planting beds before planting the rosemary. Feed with liquid compost tea once a month during the growth period. Together, they eliminate root decay while also maintaining a reasonable level of nutrition.
Use worm castings as spring top-dressing around established plants. Gently scratch into the soil surface and water deeply afterwards. This slow-release fertilizer will not burn roots or change soil structure. When combined with appropriate sun and pruning, these options will consistently outperform coffee grounds.
Read the full article: 7 Essential Steps: How to Grow Rosemary Perfectly
