How to Use Recycled Coffee Grounds in Your Garden

Composting with Coffee Grounds

Old coffee grounds are one of the best ways to add nitrogen to your compost pile, which is often a lacking element in urban or suburban composting. They can go right into the compost pail, and just give the pile a bit of a stir when you add the pail with the coffee grounds, to make sure they spread out well in the pile. You want to spread them out not only for the added nitrogen, but because they are great at retaining moisture and keeping your pile active.

Another plus: they don’t stink when kept in a plastic bag, unlike much other composting material. 

Coffee Grounds as Fertiliser

Another frequent use of old coffee grounds is as an organic fertiliser. They work well anytime you want more nitrogen and moisture in the soil, such as when you’re digging new planting beds for heavy-feeding vegetables, fruits and flowers. You can mix the coffee grounds right into the soil with a garden rake after you have turned the bed over well. Plant your new seeds or seedlings as usual, and they’ll love the nitrogen, sprouting up fast. If you’re fertilising container vegetables or houseplants, turn coffee grounds into a gentle liquid fertiliser by diluting it with water in a bottle or jug and shaking it up before each use.

Slugs Be Gone with Coffee Grounds

An unexpected bonus for many gardeners who use coffee grounds as a mulch or soil amendment around nitrogen-loving plants is that coffee keeps away crawling pests, and is especially good at repelling slugs and snails. A border of coffee grounds around plants or gardens is nearly a guarantee of slug-free gardening.

The caffeine in the grounds acts as a poison absorbed through slugs’ and snails’ skin, and they’ll avoid it thoroughly. If you have plants that slugs love, such as lilies, hostas or tender spring bulbs, surround them with some coffee mulch.

Vermicomposting with Coffee Grounds

While the list of substances that can be composted using worms is different from a plain old compost pile, coffee grounds can be used in vermicomposting with as good results as anything. In fact, their gritty texture helps the worms digest other waste.
The principle of worm bins is that the worms eat the scraps you add, then excrete a nice, dark, humus in return. But worms, like birds, have gizzards that require sand, cornmeal or other fine, gritty substances to break down their food.
Coffee grounds serve this function in a worm bin, as well as having a mulching effect on the bedding, which keeps worms moist and happy.