Coffee grounds are a popular compost material and they can do wonders for your garden — if you use them well. Not all plants will thrive on a coffee diet, so it’s important to avoid throwing those beans around.
What plants like coffee grounds, and which parts of your garden should you avoid? We’ll show you how to use coffee in your garden — the right way.
First of all… what’s in a coffee ground?
We don’t mean this metaphorically. What are coffee grounds made of, chemically speaking? Coffee grounds are full of nitrogen, a crucial plant nutrient. They’re also acidic and contain caffeine.
The biggest thing to consider when using coffee grounds as fertilizer is that coffee is acidic. Adding grounds to your soil can alter the pH, which is a good thing for some plants but not for others. You’ll want to consider the soil you’re starting with. Is it already acidic, or is it more basic? You can buy a simple pH testing kit to find out.
And what about caffeine? Though humans enjoy the effects of a caffeinated cup of joe, plants like coffee and chocolate developed caffeine to cut down on the competition. Caffeine prevents other plants from growing — allowing the caffeinated plant to make use of all of the available water and nutrients in the soil. What does that mean for your garden? Adding caffeinated coffee grounds may impede the growth of your plants.
What are the benefits of gardening with coffee grounds?
Coffee grounds provide nitrogen, a classic ingredient in most fertilizers. Plants need nitrogen to grow. Coffee grounds are also popular with worms, so if you’re vermicomposting or trying to encourage worms, they can be a great addition. And according to one study, coffee grounds can help your soil retain water, meaning you won’t have to water as often, and can diminish weed growth. Keep in mind that the same study also showed decreased plant growth overall.
Keeping Away Pests
Coffee grounds can also protect your plants from pests like slugs and snails. The grounds are abrasive, meaning these pests won’t like crawling over them to get to your tasty plants.
Some gardeners swear by coffee grounds as a cat repellent. If you often have cats digging around in your plants or using your garden as a litter box, you may want to consider adding coffee grounds to the soil.
What plants like coffee grounds?
The plants that like coffee grounds include roses, blueberries, azaleas, carrots, radishes, rhododendrons, hydrangeas, cabbage, lilies, and hollies. These are all acid-loving plants that grow best in acidic soil.
You’ll want to avoid using coffee grounds on plants like tomatoes, clovers, and alfalfa. When in doubt, it’s probably safer to put your used coffee grounds in the compost bin — or check out our list of other uses for them!
The Bottom Line
Using coffee grounds in your garden has its share of pros and cons, and we hope this article has answered your questions. Coffee can impede plant growth, but it may also keep away certain pests or alter the pH of your soil in a useful way. Plants like carrots, roses, cabbage, and hydrangeas like coffee grounds — but avoid using them on tomatoes and clovers. If you’re not sure, the compost bin is always a good place for spent coffee grounds!
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