A question I get from some readers is “Does coffee affect plant growth?”. You’ve probably seen the big coffee chains like Starbucks and the rest offering their spent coffee grounds for you to put on your own garden. This is great for them, they’re trying to be environmentally friendly, but is ground coffee good for your gardening efforts? The short answer is yes. Coffee does affect plant growth in a positive manner.
Although ground coffee is slightly acidic with a pH level anywhere from 3 to 5, it is very good for your plants. Rhododendrons and Azaleas amongst other plants and flowers absolutely love the slightly acidic pH offered by ground coffee beans. Even the more alkaline plants will benefit from coffee grounds used as mulch and organic compost, because you’ve have to put on a ton (literally) of spent coffee grounds in order to affect the natural pH of your soil.
Coffee also affects plant and vegetable growth in other ways too. Worms absolutely love ground coffee, whether in compost bins or spread and turned into the soil. Many folk have been amazed at the worm vitality and abundance in their own gardens after they’ve started using coffee grounds on their garden. It composts and mulches similarly to grass clippings. Lastly, coffee grounds are a natural deterrent to slugs if you have that problem. The slightly acidic nature of used ground coffee but more importantly the residual caffeine content in the coffee greatly reduces slug feedings depending on the concentration used.
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