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  • Naomi Stephens | Permaculture Designer

Using Coffee Grounds in your Vegetable Garden | Benefits, Myths, and Cautions

Updated: Mar 6

I like not just throwing waste out and finding some use for it.

We used to be a nation of tea lovers in Britain, but now we moved over to coffee.

With all that coffee left over, wouldn't it be good if it could be cycled back into helping our vegetable garden grow?

I've found many benefits to using coffee grounds in the garden, but there are some myths and the need to exercise caution, too.

Coffee with plants and succulents on a table

Are coffee grounds too acidic for the vegetable garden?

Studies have shown that used coffee grounds are slightly acidic at pH 6.5 - 6.8.

Once you've drunk your coffee, you've consumed most of its caffeine and acidity.

Therefore, what's left can be used in the garden.

Plants that love coffee grounds

Used coffee grounds are great for plants that love slightly acidic soils.

Some edible plants that love this slightly acidic environment are:

  • Carrots

  • Radishes

  • Onion

  • Tomatoes

  • Squash

  • Cucumber

  • Cabbage

  • Broccoli

  • Turnips

  • Gooseberries

  • Raspberries

  • Strawberries

  • Blueberries

Coffee grounds as a fertilizer

Coffee grounds act as a slow-release fertilizer when used in your vegetable garden. You can add coffee grounds to your vegetable garden by sprinkling some into your potting mix.

Coffee contains nutrients that the plants like, such as:

  • Nitrogen

  • Potassium

  • Phosphorus

While coffee grounds contain nitrogen, they shouldn't be used to replace a nitrogen fertilizer. This is because it needs micro-organisms to break down the coffee grounds to release the nitrogen, which takes much longer.

Studies by Oregon State University have shown that lettuce grown in a potting mix that contained 25% coffee grounds performed worse than lettuce grown without.

They concluded that coffee grounds weren't as compelling as a nitrogen fertilizer.

Coffee grounds as mulch

You can make it into a mulch by sprinkling it with other organic mulch you use to mulch your garden.

Ensure it is mixed with other mulch and not left to dry out on the top of your soil. Otherwise, it will prevent moisture from getting into your soil.

Other mulch ideas:

Coffee grounds as a repellent

You'll find many articles on the net advising you to use coffee grounds as a repellent.

However, this advice is anecdotal and hasn't proven 100% effective in repelling slugs and ants.

Garden myths attempted to use coffee grounds to deter ants, and it worked for a few hours. Then, the ants moved the coffee out of the way and continued their journey.

My advice is to try it as a natural option. It's said that slugs find the texture of the coffee grounds uncomfortable, and the grounds are toxic to them. It may deter 1 or 2 slugs but not a whole host of them.

Coffee grounds as a fungicide

This is a myth, I'm afraid. Coffee grounds aren't great at warding off disease.

Try using other forms of natural fungicide, such as horsetail, a common weed.

If you’ve used coffee grounds in any other ways or tried some of the methods above, then let me know in the comments below.

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