Wood Ash as Fertilizer: Free Potassium for Lawns and Gardens

Your neighbor spreads wood stove ash on grass and garden beds. Smart move—or soil sabotage? It's legit, with caveats.

What Ash Supplies

Wood ash delivers potassium (the "K" in N-P-K), calcium, and trace minerals. It's essentially free, low-grade lime—raising soil pH, reducing acidity. This benefits lawns and most deciduous trees/shrubs, especially where high-nitrogen fertilizers have acidified soil over time.

Where NOT to Use It

Acid-loving plants hate ash: rhododendrons, azaleas, blueberries, camellias, most conifers, dogwoods. Test soil pH first. If already neutral or alkaline, skip the ash.

Application Rules

• Broadcast evenly—clumps burn roots
• 1–2 light applications per year max
• Incorporate into soil or water in
• Wear a mask; ash is caustic dust

Verify With Extension Resources

Search "wood ash fertilizer" + your state university extension (e.g., Oregon State, Rutgers). They publish region-specific guidelines.

Wood ash: a traditional, effective amendment—when matched to the right plants and soil.