Can You Use Coffee Grounds on Houseplants?

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Most house plants will require fertilizing to keep them growing into healthy plants. You can buy commercially available houseplant fertilizers or use natural fertilizers like compost that you can make at home.

Coffee grounds are commonly used as a natural, cheap and readily available houseplant fertilizer. But are they any good? Are coffee grounds safe for houseplants?

It depends.

Coffee grounds can have a beneficial effect on some houseplants; however, you can drive most of these benefits if you first turn coffee grounds into compost.

Coffee grounds that haven’t gone through composting can have detrimental effects on your plants like retain excess water and promote fungal growth as a corollary. They can even inhibit plant growth and in some cases attract unwanted bugs.

In this article I will discuss the benefits you can expect by using coffee grounds for your houseplants with the caveats that come with it.

Benefits of Using Coffee Grounds as Fertilizer

If you’re a coffee drinker, you probably don’t think twice about throwing coffee grounds out in the trash.

If you have houseplants, you can make a cheap and efficient fertilizer by throwing your coffee grounds onto a compost pile instead.

The benefits you can enjoy by using composted coffee grounds on some of your houseplants include:

– Adds organic material to soil

Some plants thrive in soil that’s rich in organic materials. Composted coffee grounds are a nutritious source for the soil improving drainage and aeration of the soil.

– Contains nitrogen

Coffee grounds add nitrogen to the compost, which is beneficial to your plants. Besides nitrogen, there’s also a fair amount of phosphorus and potassium, both beneficial to your plants.

– Said to keep slugs and snails away

If your plant is prone to slug and snail attacks, ground coffee may keep them at bay. Slugs and snails will otherwise munch on the leaves of your plants.

– Said to repel cats

Cats are also believed to be put off by the smell of coffee grounds. Adding coffee grounds to the soil will discourage your cats from doing their business in your flower beds or pots.

– Beneficial to microorganisms in soil

Compost that includes coffee ground will also improve the health of the soil being beneficial to naturally occurring microorganisms in soil.

Which Plants Like Coffee Grounds

While coffee grounds can actually stunt the growth of some plants, other plants will thrive. Plants that enjoy coffee grounds compost include:

  • African violets (enjoy slightly acidic soil and require nitrogen to thrive)
  • Philodendrons (adding compost to their soil has beneficial effects on foliage and veins)
  • Christmas cacti (coffee grounds compost improves soil drainage and adds nutrients that promote blooming of cacti and succulents)
  • Jade plants (coffee grounds added to their soil promote fuller stem growth)
  • Cyclamen (coffee grounds mixed into the soil of cyclamen plants adds nutrients to the soil that favor blooming).

Coffee grounds are often recommended for acid-loving plants such as azaleas, blueberries, lilies, and hydrangeas.

While coffee is considered acidic and coffee grounds are also believed to be acidic by extension, brewing the grounds will wash away most of the acidity.

Therefore, any remaining acidity is believed to be residual and not strong enough to change the acidity of the soil in any significant way.

Because of the caffeine content, coffee grounds can act as a weed killer and prevent the growth of some plants.

Therefore, you must be careful not to use uncomposted or composted coffee grounds on some plants as you may actually be doing them more harm than good.

Avoid using coffee grounds on geranium plants, Italian ryegrass, Asparagus fern, and Chinese mustard. Don’t use it if you’re planning on germinating seeds, if you’re growing seedlings or young plants.

If you plan on using coffee grounds on your houseplants, do some research first to see if it’s recommended to use them on your particular plants.

Do Coffee Grounds Stink?

Yes, coffee grounds do stink, especially if kept constantly wet. Moisture is a breeding ground for bacteria, which promotes rotting, so it’s no surprise that wet coffee grounds come with a pungent odour.

If you’re using coffee grounds on your plants, this is yet another reason not to overwater your plants. The strong odour is said to keep pets at bay, so the stink does come with this added benefit.

Can You Mix Coffee Grounds with Potting Soil?

You can mix a small amount of composted coffee grounds into the soil to improve drainage and aeration.

Don’t go overboard, however.

Any benefits you can drive from using coffee grounds will be overthrown if you’re thinking of pumping the soil with coffee grounds.

As with any fertilizer too much of it can harm your plants, so use sparingly and in small quantities for best results.

Do Coffee Grounds Keep Bugs Away?

While coffee grounds sprinkled over the soil can deter slugs and snails, it’s not clear it will have an effect on other pests, especially if coffee grounds are worked into the soil and pests will usually hang out on the leaves of your plants.

Some gardeners suggest creating a compost tea out of coffee grounds compost to water the soil of the plants to keep bugs away.

Others suggest that if the soil that contains coffee grounds is kept constantly moist, it will actually attract bugs instead of keeping them away.

That said, pest problems are best addressed by using a targeted approach either by removing pest manually (using a wet cloth to wipe down leaves) or a pesticide (sometimes an alcohol solution or dishwasher soap works just as well).

Wrapping Up

As you can see, the answer to the question if coffee grounds are good for plants is not as clear-cut as one would like. Some plants can benefit from it, others not so much.

If you’re not sure if your plant would tolerate having coffee grounds added to their soil, you may be better off using other natural or synthetic fertilizers.

If you’re going to use coffee grounds as a fertilizer, make sure you use it composted and not immediately after a freshly brewed coffee.

Updated: October 6, 2020

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