Coffee grounds are probably the most redneck solution to growing plants. I have some sort of spider plant growing by my windowsill at work. Its previous home was a plastic cup perched on top of the office microwave. It was being given away for free.
Someone came by, saw the plant, and suggested, “I get great results when I add coffee grounds!” Oh, people and their suggestions. So, of course, I abscond to the coffee pot when I get the chance and use it to recycle some coffee grounds. The streaks of brown you see are some of the unadulterated coffee grounds that I just dumped into the pot.
The organic Colombian-based soil is a hit with fruit flies. A tiny ecosystem has developed in the dirt, and flies love to live there. The activity has slowed down somewhat, what with flies maturing and heading off to college and they grow up so quickly these days.
But… are coffee grounds good for plants?
According to one site, coffee grounds improve drainage and attract microorganisms. Given the colony of fruit flies that lived here, I can attest to the last part. It also acts like some sort of fertilizer. Plus, apparently some pests like slugs and feral cats are put off by coffee grounds, perhaps for religious reasons. Sprinkle some coffee grounds around and they’ll stay away. Allegedly.
The downside? Apparently, coffee grounds are acidic. Fresh grounds are more acidic than used grounds… so put that thought in your head the next time you drink that cup of joe and down some BOILING ACID down your throat. There are some studies that show that used grounds are pH neutral (which means NO acid). The link I posted, though, mentions some flaws in the study. The pH neutral batch was mixed in with regular soil and compost, which dilutes the potency. My method —- and I’m guessing a lot of folks methods — is just layering the coffee grounds right on top of the soil. So perhaps there is some acid lying up there.
There are plants out there that don’t like acidic soil, so you have to be careful whom to feed the coffee grounds to.
At least from my experience, the plant growing on my windowsill is looking great… but I have no idea if it was going to look that great even without its caffeine injection.