I have a couple of pots on the patio of Egyptian walking onion that are about 7 years old they get watered every day with spent coffee grounds. They are big, healthy plants. I don’t know what that says. But I’m not worried about coffee in the garden. 

 Thank you; good info. To be sure, over my life everyone has always talked about putting tea and coffee grounds in the garden and this is the first I’ve heard against it. I’ve got a lot to think about.