Even after my stint in the Army and 10 years in corporate America, I’ve never drunk a cup of coffee. Weird but true. I’m into tea.
Don’t hold that against me, I’ll go to my local coffee shop and ask for grounds and gladly accept my husband’s old filters for my worm bins, watering can and compost.
Why might coffee grounds be good for the garden?
Grounds will give us nitrogen, a bit of phosphorus and some potassium. Analysis of coffee grounds shows that they also contain many trace minerals.
Where do I find coffee grounds?
Get grounds at home of course or friends and coffee shops. If you receive a huge bag of grounds from a coffee house, immediately spread them out to dry because they will start to mold if left in a closed bag or a mound on the ground.
Wear gloves when handling lots of grounds because the coloring and caffeine can seep into your skin. A friend of mine who is a builder, once told me about one of his clients who had the brilliant idea of staining wood beams with coffee grounds. She had a great time using her bare hands to massage the grounds into the wood. After her heart starting racing and her body started shaking, they advised her to go to the hospital. She ended up in the hospital with caffeine poisoning! Once I learned about this potential health hazard, I kept bags of grounds away from my kids – although it is soft and tempting to play with. I know, I’ve done it before!
Which plants may benefit from coffee grounds?
I use coffee grounds mostly on non-fruiting vegetables such as lettuces, cabbage, spinach and other greens. They can also serve as a good nitrogen source in the compost pile.
A study from Linda Chalker-Scott entitled “Coffee Grounds-Will They Perk Up Plants?” shows some evidence that grounds might enhance beets, cabbage and spinach but could potentially damage tomatoes. See the Coffee Grounds listing in the Bibliography if you would like to read more.
Combine coffee grounds with…
Leaving coffee grounds directly on the surface is tricky because they tend to dry up and leave a crust. I’ve found it’s more beneficial to mix with other ingredients. I’ve combined them with crushed eggshells, kelp and compost to maximize nutrient content.
Coffee Grounds in Compost Recipe
Nitrogen-rich scraps help get the compost heap rolling. Add leftover coffee grounds to the pile along with an equal amount or a bit more brown materials (dried leaves, straw or shredded paper).
Coffee Grounds Liquid Fertilizer Recipe
To use coffee grounds in liquid form, let one cup of grounds soak in one gallon of water (or 5 cups of grounds in a 5 gallon bucket). Let it sit for a couple of days and then saturate the soil around your plants. I always like to water the plants first before adding any liquid fertilizer for even distribution.
Feed Composting Worms with Coffee Grounds
Pulverized grounds, vegetable scraps and cantaloupe/watermelon rinds get devoured quickly in my worm bin. Don’t overdo it though. In my experience, coffee grounds should be no more than 5-10 percent of the mix.
Coffee Quick Tips
- Coffee grounds applied directly to the soil don’t work right away. Microorganisms need time to break them down. That is why I like to use them dissolved in water as a soil drench.
- If you score big bags of coffee grounds from a processing plant or coffee shop, and have a large garden, add a thin layer of grounds on top of the soil and water well (months before you plant).
- Coffee grounds are commonly used on plants that love acidic soils such as blueberries, evergreens, azaleas, roses, camellias, avocados, and certain fruit trees. However, contrary to popular belief, used grounds are not that acidic. People assume they are because coffee is considered acidic. Most of the acid leaches out into the cup of coffee. One application of coffee grounds will probably not noticeably adjust the acidity of the soil. Read more under the topic “Coffee Grounds” in the Bibliography.