Gardening: Using coffee grounds to perk up your soil
Though I moved to a condo a couple of years ago and no longer have a vegetable garden to tend, I haven’t given up my habit of saving spent coffee grounds. I dust them over the surface of the soil around the three hydrangeas I planted in front of my patio and also scatter them in the potted tomatoes that reside on my porch.
I don’t have a water source outside, so watering is done by a sprinkling can and the shrubs are on their own. So far, in spite of the hot dry weather they’re doing fine.
Due to the popularity of cold brewed coffee there is a huge increase of used coffee grounds around the U.S. that need to be disposed of and due to their nutritive content they may also have value as an organic turf fertilizer, so Texas A and M is doing a 2 year study evaluating their use.
Spent coffee grounds have approximately a 2 .5 percent nitrogen content and a carbon to nitrogen ration of about 20 to 1 and that puts them in the range that’s fairly desirable as a fertilizer application for turf, according to the ongoing Texas A and M study.
Besides the nutritional benefits of spent coffee grounds, they’re good for improving soil structure, loved by earth worms and support beneficial bacteria that control diseases and repel insects.
If you top dress your lawn in fall or spring, including spent coffee grounds in the mix is a smart thing. Easier yet, just dry them out on cookie sheet and toss them out in the yard.
Composting coffee grounds increases their nutritive value a bit, but if you choose to do this it’s recommended that they be limited to 20 percent of content materials.
Not to worry about the pH level of spent grounds – in their fresh form they are very acidic, but once used, the acid is leached out and the material rates around neutral.
The good news is you don’t have to dig the coffee grounds into the garden soil. Our friends the earthworms will carry them down into their tunnels for you.
If using the grounds as mulch do not apply it too thickly as they may pack down and repel water. Mixing the grounds with shredded leaves and/or compost will make a perfect combination.
I buy my coffee pre-ground so I use the bean grinder to pulverize eggshells into powder that also goes into the tomato pots. Old habits die hard.
Nancy Szerlag is a master gardener and a Metro Detroit freelance writer. Her column appears Fridays in Homestyle. To ask her a question go to Yardener.com and click on Ask Nancy. You can also read her previous columns at detroitnews.com/homestyle.