Are eggshells effective for tomato plants?
Written by
Julia Anderson
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Eggshells have long been the subject of debate among tomato growers. Eggshells have calcium in them, but raw crushed eggshells break down slowly, often taking upwards of 6-12 months to provide nutrients to the plant. I have amended the soil with eggshells in simultaneous side-by-side tests with tomato plants and tomatoes grown with calcium nitrate had 30% less blossom-end rot, than the eggshell-amended soil.
Eggshell Limitations
- Decomposition rate: 8-12 months for partial breakdown
- Bioavailability: Only 4% calcium released annually
- Application: Must be baked/ground for faster action
Effective Alternatives
- Calcium nitrate: Dissolves in water for immediate uptake
- Gypsum: Improves soil structure while adding calcium
- Liquid calcium: Foliar spray for rapid absorption
To promote long-term enrichment of soil be sure to compost your eggshells first by crushing them into powder, mixing them with coffee grounds, and allowing them to go through a microbial breakdown. We saw our clay soil improve after eighteen months of adding two cups of pre-composted eggshells per square foot each year.
Eggshell Composting
- Grind shells: Use blender or mortar/pestle
- Mix ratios: 1 part shells to 3 parts greens
- Cure time: 90-120 days for optimal breakdown
Immediate Deficiencies
- Foliar spray: 1 tbsp calcium nitrate/gallon water
- Frequency: Apply every 10 days during fruiting
- Avoid overuse: Can inhibit magnesium uptake
Strive to balance quick responses with a focus on long-term soil health. That is why I keep powdered eggshells in my compost pile for slow enrichment and have a spray bottle of liquid calcium ready to go when a crisis arises. Your tomatoes will repay you with firm, injury-free skin, and excellent flavor.
Read the full article: How to Grow Tomatoes: Complete Beginner's Guide
