Use Coffee Grounds in the Vegetable Garden

 | 
Save coffee grounds for use in the garden.

It’s great to sip coffee in the garden, but when you’re done, don’t toss the grounds in the trash. Using them in the garden will help you produce more veggies.

OK, so get yourself a cup of coffee and let’s talk gardening!

I get the privilege of monitoring and replying to comments on our website, and I love joining in the conversation about vegetable and herb gardening. Sometimes, I get the opportunity to help fellow gardeners out with their questions, which is the most fun of all. Yesterday, a reader named Carlo asked this intriguing question on our Bonnie Herb & Vegetable Plant Food page:

“I read that coffee was supposed to be good with acid loving plants like tomato, so can I use ground coffee for extra nitrogen and pest repellent and with the Bonnie Plant Food, or will this be too much nitrogen at the same time that it might burn my plant?”

Since drinking coffee in the garden is one of my favorite early Sunday morning activities, now seems like a good time to let you know what Carlo and I found out.

Coffee grounds make a great addition to the compost.

Yesterday, we took apart our compost bin and found this great “black gold” (minus the eggshells, which didn’t break down). Much of it started as coffee grounds.

As I told Carlo, I have been using coffee grounds in the vegetable garden for years, believing from hearsay and my mother that this evidence of my daily coffee habit could be good for the garden. A Starbucks fanatic, mom takes the coffee company up on their offer of free Starbucks “Grounds for Your Garden” in addition to adding more from her own home brew.

At my own home, I make a lot (and I do mean a LOT) of coffee, both in a drip machine and a French press. All of it ends up in the garden somehow. Most goes into our compost pile, but I do sometimes deposit grounds directly into the garden, or swish the French press grounds around with some water and pour the slurry into the soil like compost tea. But like Carlo, I’ve never checked to see if there’s any science backing up this practice.

Don't put coffee grounds in the garden without mixing into the soil first.

Don’t just dump coffee grounds on top of the soil or mulch (as shown above). The dried grounds can wick moisture away from soil and plants. Instead, mix the grounds into garden soil.

So, to the Internet, where I found a great study from Oregon State University Extension Service that you might find interesting, too. (Of course it would be from the Northwest, regional capital of coffee!) The report dispels the myth that the grounds are acidic (they are actually close to pH neutral) but confirms that they do contribute nitrogen to compost and to the soil when used in tandem with a fertilizer that contains some nitrogen, such as our Bonnie Herb & Vegetable Plant Food (an 8-4-4 mix). Coffee grounds also improve soil tilth (the physical condition of soil) and soil structure, and they may repel slugs and snails, too. Read more of this OSU study to learn how and when you should use coffee grounds in your garden.

It turns out that mom and Starbucks were right. Coffee is good for your garden. So drink up. Cheers!