I have access to about 20 pounds of coffee grounds everyday. I have put a lot in my 1/4 acre garden. I noticed some of my corn was very this year. Did I get too much in some areas? Also are they good for grapes, blueberries, lawns, and all other garden plants?
Gardeners, myself included, have long been using coffee grounds in the garden. With the increase in coffee shops we are seeing an increase in the use of grounds in composting and soil preparation. Associate Professor of Horticultural Science at the University of Minnesota and author Jeff Gilman shared some insights in his book The Truth about Garden Remedies.
Coffee grounds are acidic but when spread over the soil have a minimal effect on the soil pH. They do, however, contain alleleopathic chemicals that can inhibit growth in certain susceptible plants. Once the coffee grounds fully decompose this is not a concern. Lettuce seems to thrive in coffee ground amended soil while tomatoes do not. Unfortunately there is not a complete listing of plants that thrive or decline in coffee amended soil.
Adding large quantities of fresh coffee grounds into the soil can temporarily tie up the nutrients. Once the grounds decompose they release these and more nutrients for the plants to use. Consider working some of the grounds into the soil in the fall with shredded leaves and herbicide-free grass clipping. Share some of the grounds with friends, compost some and limit the amount of grounds added to your growing gardens.
Another positive to coffee is the caffeine. US Dept of Ag scientists recently found caffeine repels and kills slugs. Currently there are no caffeine based slugacides but those mulching with coffee grounds may see a decrease in slug damage.