Coffee in the Garden: Enjoy it Twice

I love coffee.

Many of us love coffee.

We all love gardening so…………..

I enjoy nothing more on summer mornings than sitting on my deck, sipping a warm cup of coffee, enjoying the quiet sounds and watching the world come alive. I look out over the garden, smell the fragrance, listen to the birds and just enjoy the moment. A lot of coffee gets consumed in my house. I also have a lot of garden beds in need of good compost. So I take advantage of this ready source of nitrogen and add coffee grounds to my compost. In doing so, I get to enjoy the benefits of coffee twice.

How good of a source of nitrogen is it?

Used coffee grounds are an excellent source of nitrogen, and a few other nutrients and minerals. Depending on which scholarly article you read, coffee grounds are somewhere around 3% nitrogen by volume. So on it’s own, coffee grounds would read as 3-0-0 for NPK. They do also contain potassium and phosphorus, but generally less than 1% by volume. 3% isn’t too shabby. Now coffee alone shouldn’t be your only source of nitrogen. But when added to compost bins, it creates another diverse source of nitrogen for you.

Why wait then? Why not just add it straight to the garden beds?

You can add your grounds directly to the garden soil. However, the nitrogen in coffee grounds is not readily available for plant uptake. The grounds have a carbon to nitrogen ratio of about 20:1. If you remember your rule of thumb for compost breakdown, then you want that ratio closer to even. The coffee grounds are an available source of food for beneficial microbes, but that process can rob the soil of it’s existing nitrogen. So you can add them, but you will also need to supplement with additional fertilizer, so whats the point? Eventually when the coffee grounds break down, they will provide nitrogen, but that takes time and could represent a good portion of your growing season. You should not  expect any results right away.

But coffee is acidic……

Adding spent coffee grounds to your soil, or using compost of which they are a part will not make your soil more acidic. Used coffee grounds have a pH of between 6.5 and 6.8. That is slightly acidic, but pretty close to neutral. The brewing process removes most of the acid from the grounds because it is water-soluble. Your coffee ends up being acid and the grounds neutral. So don’t be scared by this urban myth. It’s based on only knowing half the info. This all being true, fresh ground coffee poured around your hydrangeas and watered in, should in theory cause a color change. I have never played around with it, but it sounds like a fun experiment.

Where to get the grounds

Kitchen grounds bucket with some vegetable scraps in it

If you drink coffee, you have grounds. But that alone may not add up to enough to be meaningful. Luckily for us, there are a lot of other coffee drinkers in the world. So there are lots of grounds available. There has been a lot written about making deals with coffee shops, convenience stores and the like for their grounds. They almost always have coffee brewing, and they produce a lot of grounds. But realistically, they don’t want a stinky bucket of used grounds underfoot. So you can ask, but you will need to stay on good terms with them. Try smaller, boutique coffee shops. They generally thrive on being environmentally friendly, and may jump at the chance to help you out.

Friends and neighbors are always a good source too. Especially if they share in the bounty of your harvest. This way you can sell it as they are really helping themselves by helping you. If you are brave you could leave out a bucket, pail or tote with a sign, but who knows what would end up in it. I leave that to your discretion.

I have discovered a gold mine of free used grounds. Work. We plow through coffee at work. Most offices do. Last spring I put out an empty #10 coffee can with a sign on it explaining why I wanted them. It was a hit. I was lugging home two of these containers a week. The cleaning lady even helped me out because in case you don’t know, wet coffee grounds are heavy. So I effectively removed over 10 pounds from the trash for every can of grounds I took home. It didn’t take long to fill a 60 gallon Rubber-made tote.

This year I decided I didn’t need that much. So I settled on an alternative. Like many offices, the traditional coffee maker setup is being slowly phased out in favor of Keurigs. No more buckets of grounds. Now I get bags of spent k-cups. I sent out a email to everyone in my general vicinity at work, and told them why I wanted the grounds, and that I had a bin labelled for used k-cups in my cubicle.  All it took was a waste bin from an empty cubicle and a label maker, to be in business. Once a week I get a decent sized bag of k-cups to bring home.

K-cups from work being processed

The down side of this is, that it requires some processing on my end. You just take a knife, run it around the foil rim, peel it back, then once around the inside to loosen the grounds. Give it a tap and out they come. K-cup grounds are a finer grind. So per unit of volume you get more coffee grounds than traditional grounds. The finer grind should also help with the breakdown process, as a finer grind has more surface area. More surface area makes them more chemically reactive.

So consider this resource when you are hunting for things to compost. When organic matter like coffee grounds gets to a landfill, it gets buried and decomposes anaerobically. That means it produces methane. But by composting you help eliminate this source of green house gas. So all you organic gardeners, urban homesteaders and mad scientists need to take advantage of this resource.

Stay green. Help the planet and in turn help yourself.

A parting word of thanks to all you new subscribers. I am touched by the fact that you liked what you read enough to subscribe. I will keep trying to turn out qualify content for all of you.