Are coffee grounds good for radishes?
Written by
Benjamin Miller
Reviewed by
Prof. Martin Thorne, Ph.D.When applied appropriately, coffee grounds can noticeably elevate the growth rates of radish crops. I nearly hindered the growth of my crop due to a mistake over applying fresh grounds, but recently I combined one cup of coffee grounds into ten gallons of finished compost. Radishes will tolerate some acidity, so it is best if you are testing your soil pH at least once per month. Coffee grounds also contribute to improving drainage in clay soils and provide trace minerals, including magnesium.
Benefits
- Organic matter: Improves soil structure
- pH adjustment: Lowers alkalinity slightly
- Pest deterrent: Repels root maggots
Risks
- Nitrogen imbalance: Ties up nutrients if uncomposted
- Fungal growth: Promotes damping-off in humid climates
- Over-acidification: Avoid in soils below pH 6.0
Aid your overly-fertilized soil by leaching it with 5 gallons of water per square foot. Use dolomitic lime to raise the pH. 1/2 cup per plant saved my soil pH from 5.2 acidity. If grounds cause leaves to be yellow, convert them to alfalfa meal for nitrogen.
Immediate Action
- Remove visible grounds from soil surface
- Apply 1" compost buffer layer
- Water with Epsom salt solution (1 tbsp/gal)
Long-Term Fixes
- Test soil every 2 weeks
- Switch to worm castings
- Rotate planting beds annually
To attain optimal results, compost grounds for a minimum of 60 days before use. My vermicompost bin breaks down compost grounds most quickly with the help of red wigglers that can process more than 2 cups daily. Combine the grounds with crushed eggshells (1:1 ratio) to retain beneficial acidity. In trials, radish roots grown in this manner measured 15% increased girth.
Read the full article: How to Grow Radishes: 7 Pro Tips for Bumper Harvests
