I was getting coffee and picking up my bakery bread order last weekend at the local coffee shop.  Next to the register was this bag of coffee grounds, just inviting me to take it home for the garden.

While we’re not huge coffee drinkers, we drink enough that there are a few handfuls of grounds headed to the the trash each week.  Between that and the bag of grounds I brought home with me, I thought I should look into using grounds in the garden to see if I can help the environment and my garden at the same time.  It seems that it’s not quite as simple as sprinkling it in the garden to get results.  Of course there’s the anecdotes that it’s the magic potion that turns a so-so garden into a breathtaking place.  But, from a more scientific point of view, that may not always be the case.

Here’s what I’ve learned:

• Lab tests show that the grounds contain useful amounts of phosphorus and potassium, are a low-level source of nitrogen (about the same as grass clippings) and also contain minor amounts of calcium, magnesium, copper, and other trace minerals, carbohydrates, sugars, some vitamins, and some caffeine.
• Coffee is acidic, but coffee grounds are closer to neutral so not really that useful for acid loving plants like azaleas
• They are great in the compost bin, both for their nutrient value and their ability to make it “hot”.  Add them as part of the “green material” not brown .
• People have reported good results adding it to the soil around hostas, roses, and on their lawns.  Especially when there is an underlying soil issue, like clay or damaged soil.
• Use as transplant fertilizer for tomatoes, squash and leafy vegetables by placing a handful in the transplant hole.  Seems to give those young transplants a nutritional boost.
• Worms love coffee grounds (in moderation, of course).  Use them in soil to attract worms to the garden, or in a worm composter.
• Use to make a liquid feeder.  Mix grounds with a bucketful of water and leave sit for a day or two to make a nice carmel colored tea to use as a liquid fertilizer.
• Grounds placed around the base of plants are a slug deterrent.  Seems to be an ant repellent as well.

I didn’t read anything about them being harmful to the garden in reasonable amounts, so I think this year the grounds will be sprinkled in some of the older gardens that could use a little perking up.  I’m also planning to use them around my hostas as a slug repellant as they start to do their damage mid-summer.  Maybe someday I’ll get a compost pile going and they’ll be a great addition, but that’s not in the cards right now though.

Do you use your coffee grounds in the garden?