I have to take the flip side with coffee grounds, they contain caffeine which is an herbicide! Using coffee and coffee grounds stunted the growth of my autos and caused them to take 130 days instead of 65 days! I learned a lesson there and no more taking the chance that I did not get the caffeine washed out of the grounds. I used it for the PH down affect,,,
If you use them be sure to wash then well,,,,, or use decaffeinated,,,