Should You Use Coffee Grounds for Plants? There Are Pros and Cons

Reusing coffee grounds on plants may help fertilize your garden, but only when applied indirectly.

Key Takeaways

Many creative ways are shared online for using spent coffee grounds tofertilize plants.

However, DIY garden remedies and anecdotal recommendations are not always grounded in fact.

Studies have shown both positive and negative impacts of using coffee grounds on plants.

The effects of using coffee grounds on plants also vary depending on their use.

Some gardeners use fertilizer teas made directly from spent coffee grounds andnot composted coffee grounds.

For best results, use composted grounds and not fertilizer teas.

For example, brewed coffee is highly acidic, but spent coffee grounds are not.

Lets look at the nutrients found in spent coffee grounds and what benefits they can have on plants.

Nitrogen-rich proteins make up about 10 percent of the spent coffee groundsand plants use a lot of nitrogen.

The coffee grounds must first be broken down through composting or natural decomposition.

By reusing spent coffee grounds for plants, you’re helping reduce food waste.

This is a great way to gather large amounts of coffee grounds to use in your garden.

This can encourage fungal growth and reduce airflow to the plant roots.

Without good bacteria, plants may be exposed to disease and pests.

A popular recommendation is to make fertilizer tea from composted coffee grounds and use this tofeed houseplants.

However, Chalker-Scott says, …there is no science supporting the use of compost tea for anything.

Adding finished compost to potting mixes is another great way to reap the benefits of composted coffee grounds.

Finished compost can be integrated with potting mix to stimulate soil health and plant growth.

Potting mixes can be amended with up to 30 percent finished compost.

Some plants do not benefit from adding coffee grounds to their soil.

Plants like lilacs and lavender prefer alkaline soil, so the slight acidity may harm them.

The caffeine in coffee grounds can also harm some herbs and geraniums.

Be sure to research the optimal conditions for your plants before adding coffee grounds.

And remember, the best way to add coffee grounds is indirectly through composting.

Depending on the coffee filter material, you may be able to compost it along with the coffee grounds.

you could compost coffee filters made from paper or other compostable materials.

Do not compost those made of synthetic materials (like nylon or plastic).

As we separate fact from fiction, lets look at recommendations for using coffee grounds to lower soil pH.

Although coffee is quite acidic, the grounds that remain after brewing are not considered acidic.

Though this research has not been conducted with potting soil, we can assume similar results.

Washington State University Extension.Using Coffee Grounds in Gardens and Landscapes.

Accessed May 16, 2023.

2023;30(36):86218-86231. doi:10.1007/s11356-023-28386-z