Gardening with Coffee Grounds: Myths and Methods Explored

Used coffee grounds and the garden

We often get asked whether you can use used coffee grounds in the garden, so we’ve been investigating, and here’s what we’ve found.

The Debate on Coffee Grounds in Gardening

There are many advocates for putting used coffee grounds to use in the garden – but, beware. There are as many “experts” who say they are almost “death” to gardens.

Coffee Grounds in Compost: A Green Compost Material

Just add them to the heap and let the compost bin do its job. But if you drop coffee grounds in the compost bin, remember they qualify as green compost material. You may want to balance it with brown compost material.

Coffee Grounds as Soil Acidifier and Fertilizer

This is fine for plants that like acidic soil but is likely to be a problem for those that don’t. However, it is debatable whether spent coffee grounds are even acidic.

Coffee grounds are rich in nutrients, especially nitrogen. But remember they should be spread in a thin layer to reduce the concentration of caffeine in one area. Too much caffeine can “poison” the soil and stop other nearby plants from growing.

The Impact on Weeds, Pests, and Mulching

It is argued by the “pro” lobby that spent grounds are good for deterring slugs and snails. This is another “undecided” in that some experiments have found that slugs avoid the grounds, others that it makes no difference at all.

The jury is out on mulch too. Many gardeners have found that using coffee grounds as mulch can be very destructive to the plants.

A different approach is required with coffee grounds. A thick layer of mulch with coffee grounds will lead to caffeine-rich soil and stunted plants. This is especially true of plants that dislike acidic soils, such as lavender, tomatoes and asparagus.