Coffee Grounds In The Garden


Old coffee grounds for the garden

Your local cafe is usually very happy to give away free coffee grounds. A typical Australian café produces about 80 kg of coffee grounds every week. This often ends up in landfills, so you are helping them get rid of a waste product they usually need to pay to get rid of.. So they’re keen. But the question is…

Are Coffee Grounds Good For The Garden

Yes indeed they are – with a few caveats to keep in mind. If you’re fond of gardening, coffee grounds are not a waste product. They are a valuable product you are delighted to get your hands on. Coffee grounds are rich in potassium and nitrogen, along with carbon, so they can really feed your garden’s soil.

There are some gardeners who will tell you that using coffee grounds in the garden is either of little use or even damaging. Much of this negative to neutral opinion comes from failure to follow a few key principles of proper coffee grounds use. Like anything, the devil is in the detail.

Let’s go through the main issues and decide if they are indeed worth it or not.

Are Coffee Grounds Good For Compost

On their own and without being mixed with other material, used coffee grounds are too acidic to be used as a compost. To incorporate them into a good compost mix, you need to mix them with other organic waste such as sawdust, straw, leaf mold, or other fibrous material. Sawdust works especially well when mixed with coffee grounds in a 50/50 ratio by volume. Be certain to keep away from the sawdust from treated timbers and make sure it rots completely so that the sawdust won’t rob the soil of nitrogen like when it is ‘too green’.

Are Coffee Grounds Good For Mulching

There is no doubt about the usefulness of mulching, and coffee grounds can play an important role in it. Because it can be hard to get compost, straw, or other raw materials in large enough quantities and at cheap enough prices, coffee grounds can be a great addition to the whole process.

However, you need mix the grounds in with some fibrous material before you spread it on the soil. Do not spread them directly on the soil, because this will cause more problems than its worth.

Some say the negative effects of using straight coffee grounds as mulch come from the plants absorbing the residual caffeine in the grounds. While it is certainly true in some cases for some species of plants and with an especially strong batch of coffee, it is probably due to too much acidity causing stress on the plants.

So mix it with other mulching materials, and don’t put it on too thick, both for the purpose of keeping it from being too acidic and also so the ground doesn’t form an impenetrable layer that doesn’t let the moisture through to the soil below.

Make sure to rake the coffee grounds into the top layer of soil so they don’t glob together. Otherwise, blend coffee grounds with various other ingredients like compost or leaf mold before you use it as a compost.

Are Coffee Grounds Good As Fertilizer

They make an excellent slow-release fertilizer. Just sprinkle small amounts of the grounds around plants to allow the nutrients to release slowly.

Coffee grounds contain an appreciable amount of important nutrients. They are a nitrogen-rich natural material, perfect for your garden. They also contain potassium as well as phosphorus and other micronutrients. The quantities and percentages of these nutrients may vary, but this doesn’t matter if you spread it around as a slow-release fertilizer – as long as you don’t over do it. Your plants will use the nutrients they need, when they need them.

Are Coffee Grounds Good As Worm Food

Many keen gardeners will say that their worms like coffee grounds, so small amounts can be added to your worm farm on a regular basis. If you don’t have a worm farm, then get one because what they produce for your garden is just wonderful. You can also throw in paper coffee filters for the delightful little critters to munch through and turn into gardening gold. Howerver, there are a few guidlines to follow in the process:

  • It is best to add coffee grounds along with other food scraps and give it all a bit of a mix up in the process so the grounds are evenly distributed. So for example, if you are adding fruit and veggie scraps, fruit peels, etc, stir in the day’s coffee grounds so there is no single concentration of them.
  • If you haven’t fed your worms for a while, it is best not to give them coffee grounds as the break of their fast. They are too rich a source of nitrogen (as much nitrogen as cut grass) to feed to the worms on their own. Too much of a good thing is no longer a good thing.

Are Coffee Grounds A Natural Pesticide

One oft-repeated piece of advice is to spread dried coffee grounds around plants that are prone to snail and slug damage. It is important to note here that others say that this is a waste of time and will act as a negligible deterrent. For those who believe, there seems to be 2 different theories about why this works for them: 

  • The rough texture of the grounds clings to the soft-bodied slugs and snails as they attempt to move across a coffee grounds barrier, which causes them to avoid it.
  • The high levels of caffeine in the grounds acts as a deterrent to the snails and slugs so they have a tendency to avoid it.

Coffee Grounds and Dogs


Coffee grounds can be toxic to dogs if they eat large enough amounts of it. So if you have one of those doggies who just scoff down anything it finds in the yard, you should be careful to work any coffee grounds into the soil or other mulch so your darling little pooch can’t inadvertedly poison himself. Alternatively, just compost it in the compost heap instead.

On the good side, it would take a very large accidental meal of the grounds to make a dog sick, but as they say, better safe than sorry.

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