I bet there is a big crossover between people who love coffee and those who love gardening. Could the two possibly intersect? Coffee grounds are often advertised as one of those miracle garden tricks you can do right at home, but what plants actually like coffee grounds? Let’s find out!
A daily cup of coffee (or, let’s be real, two cups) can lead to a lot of coffee grounds. Why not try to use them up and let our plant babies benefit from them?
There are a ton of misconceptions and debates surrounding coffee grounds. What I can tell you is my personal experience with plants that actually like coffee grounds as well as some studies to show you where I’m coming from.
This post will cover…
- Coffee Ground Uses in the Garden
- Nitrogen Rich
- Worm Food
- Coffee Grounds Are Acidic…Sometimes
- So…What Plants Like Coffee Grounds?
- How to Use Coffee Grounds
- Frequently Asked Questions About Using Coffee Grounds
- More Posts to Read
Coffee Ground Uses in the Garden
Coffee grounds have swept TikTok and Instagram feeds as a soil amendment, but how true is it?
Yes, coffee grounds have plant nutrients, though it’s not a super significant source. You will find phosphorus, magnesium, and some others in it.
People are also touting its use as mulch, layered on top of plants, to suppress weeds and retain moisture. While it can work as a mulch, it should always be mixed in with other mulch rather than used on its own. Left on top of the soil, it can become compacted and cakey.
All in all, coffee grounds are great for adding organic material to your soil. And when we add organic materials, we improve water retention, drainage, and circulation. Plus, it attracts microorganisms!
To get the most out of coffee grounds, you should use it after it’s been composted rather than fresh.
Nitrogen-rich proteins account for 10% of coffee grounds, making them a rich nitrogen source. As the soil decomposes, the nitrogen levels may spike and then lower themselves back down to 11 over the course of the year.
Being a high source of nitrogen, it’s also great for the compost pile. While it may be brown in colour, coffee grounds are considered a green for your compost recipe. Once it’s composted, it becomes a great soil amendment.
I also include coffee grounds as part of my worm’s diet for my vermicomposting bin. While some critters, such as slugs, are said not to like coffee grounds, worms seem to love it. In fact, a study showed that a vermicomposting bin with coffee grounds produces higher-quality worm castings than those without.
Coffee Grounds Are Acidic…Sometimes
One of the biggest misconceptions surrounding coffee grounds is its acidity. A good cup of Joe tastes so strong partly due to its high acidity, which makes people believe that the coffee grounds will also be acidic.
The truth is that the acid in coffee is water soluble, and much of it goes into your coffee mug.
The pH of coffee grounds can be acidic after decomposing, but it can also be neutral and even alkaline at times. So overall, the acidity of coffee grounds is inconsistent, though it does tend to lean towards slightly acidic to neutral.
So…What Plants Like Coffee Grounds?
While it may not be consistently acidic or high in acidity, it’s still good to use for those acid-loving plants or those that like a balanced pH. This is especially true for compost that hasn’t decomposed yet. So go on and add it to your blueberries, azaleas, and heathers, who will cross their fingers for some more acidity.
If you want to improve your soil’s water retention, use decomposed coffee grounds. Then, the opposite is true. Don’t use coffee grounds if you want drier soil for drier plants.
How to Use Coffee Grounds
Unless you happen to own a coffee shop, the daily amount of coffee grounds you produce from a cup of coffee can be added to your compost or mixed directly into your gardening bed. Sprinkle it on the surface and then mix it in.
Remember, too much of a good thing is bad. The coffee grounds can build up specific nutrients and overload the plants. Or, it might compact and actually make your soil hydrophobic. No more than 20% of your compost should consist of coffee grounds.
Frequently Asked Questions About Using Coffee Grounds
Coffee grounds help aid water retention, so avoid any kind of plants that like drier conditions. You also want to avoid anything that prefers alkaline soil, such as tomatoes or brassicas. However, once it’s decomposed, it’s fairly safe to use for any acidity.
You can use the coffee grounds trick with your potted plants and houseplants as well. This is great for soil that’s become hydrophobic, as coffee grounds can help increase water retention. Just be sure to sprinkle it on top of the soil and then work it in for it to work. No more than a little! Avoid any plants that like alkaline soil or prefer it dry, like succulents and cacti.
Collect your grounds separately if you want to add them straight to your soil. Sprinkle a little on top to mix in with the same frequency you would fertilizer. Otherwise, let it decompose in your compost pile, adding no more than 20% of the total volume of coffee grounds.
Is it ok to use decaffeinated grounds?
Why does my rubarb plant never get any bigger after five or six years
Hi Wendy, does this help? https://gardentherapy.ca/rhubarb-plant/
This is the best blog on here today and everyday!!! I learned more here than I probably ever have. And I have a wonderful Down Syndrome nephew and he is exactly like your little sister!!! I so enjoyed this and will keep it and read it again. Right now, I’m headed to save my coffee grounds. Thank you so much for this!!!❤️
Thank you Jamie.
I have a somewhat complicated (to me) question. Suppose you have a raised bed garden, what would be the % ratio of compost/garden soil?
I have a bunch of soil recipes in my Garden Alchemy book where I write a lot more about the ratios. But also there is some info here https://gardentherapy.ca/soil-recipes/
For non-coffee drinkers, Starbucks will save their coffee grounds and give them away.