Using Coffee Grounds in the Garden
You may have heard a lot of buzz around using spent coffee grounds in the garden as the practice has gained a lot of popularity in recent years. Many people are using them as organic fertiliser, mulch, pesticide, or compost so is it something you should be doing as well? Unfortunately it’s not a black and white issue as there are certain complexities to using coffee grounds in the garden that make it unsuitable for your needs. Make sure you have all the facts first to decide if used coffee grounds are right for your garden. Here are some tips and common questions to get you started.
Do coffee grounds make soil acidic?
If you’re thinking about using coffee grounds in the garden then the first thing to consider should be coffee’s acidic properties. Even used coffee is slightly acidic so it’s best to find out first if the plants you are growing respond well to acidity or not. Spent coffee grounds are less acidic than fresh coffee but still have a typical pH level of around 6.5 to 6.8 (7 being neutral).
Can coffee grounds be used as fertiliser?
Coffee grounds can indeed be used as fertiliser in the garden and this is one of the most common uses for used coffee grounds. You could use fresh coffee grounds also but this would obviously be a less cost-effective method seeing as used coffee is probably heading for the bin anyway. Also used coffee is likely to contain less caffeine which makes it the more desirable fertiliser option.
Coffee grounds are rich in nitrogen as well as potassium and phosphorus which are all essential soil nutrients. Nitrogen helps plants grow as it’s a component of amino acids which form proteins. It’s also essential in the production of chlorophyll which absorbs the sunlight needed for sugar production.
When using coffee grounds as fertiliser, make sure to spread them out evenly over the soil in a thin layer. The main risk of coffee grounds in the garden is the residual caffeine stunting plant growth due to its allelopathic properties. However it would take a lot of caffeine to do this so spreading the grounds out evenly and thinly reduces the chances of caffeine clumping together and causing harm to soil and plants. You could even try using decaf coffee grounds if you’re concerned about caffeine. Generally you want to avoid spreading coffee grounds on recently seeded areas or germinating plants.
Another reason to spread the grounds thinly and evenly is that will minimise any negative impact from coffee’s natural acidity – unless you’re dealing with acid-friendly plants such as hydrangeas and blueberries or even some root vegetable such as radishes or carrots.
Are coffee grounds good as mulch?
Mulch provides many benefits to plants and if you’re serious about gardening you’ll want to make use of it. It’s not always easy to obtain though so people often turn to coffee grounds as a substitute. However the results can be very destructive to plants so it’s best to adjust your approach.
You’ll want to avoid any thick layer of coffee ground mulch or any large clumps as the caffeine content may stunt plant growth. Use a very thin later or try mixing the grounds in with other organic matter. It’s important to make sure plants don’t get overwhelmed by caffeine and also that their water supply is sufficient.
Are coffee grounds good to compost?
Coffee grounds can definitely be composted and this practice should be encouraged. The coffee industry is even making efforts to ensure products such as pods are compostable.
Just add all the spent grounds in the compost heap and let nature take its course. If you’re adding coffee grounds to the compost bin, remember that they count as green compost material. Consider balancing it out with brown compost such as dry leaves.
Coffee grounds can be used in vermicompost too as earthworms are apparently big fans of coffee! If you have a worm bin, try adding your spent coffee grounds and paper filters to help the little fellas out and attract more of them. This is a simple method which yields good results.
Do coffee grounds get rid of weeds?
Due to their allelopathic properties, coffee grounds in the garden can help stunt the growth of weeds. However you’ll need to make sure the grounds are strategically places so they don’t also harm your other plants.
What pests do coffee grounds repel?
Coffee grounds in the garden do have a limited effect in repelling pests such as slugs, snails, beetles, fruit flies, or mosquitos. Similarly coffee grounds can also deter household pets in the garden. Cats are particular adverse to caffeine. This way you might be able to deter your pets (or your neighbours’ pets) from using your flowerbeds as a litter tray.
Which plants benefit most from coffee grounds?
Since coffee is slightly acidic, its best suited to acid-friendly plants that thrive in acidic conditions. Such plants include hydrangeas, roses, blueberries, azaleas, lilies, or rhododendrons. Root vegetable such as radishes or carrots have also been seen to benefit from coffee grounds.
Which plants do not like coffee grounds?
Coffee grounds are not to every plant’s taste – especially due its acidic nature and caffeine content. This 2016 study found that the growth of broccoli, leek, radish, viola and sunflower was inhibited by the addition of coffee grounds.
Garden Experts
Get in touch with us to take advantage of our award-winning garden design & landscaping services. We serve Gloucestershire, Oxfordshire, Warwickshire, Wiltshire, Berkshire, and Buckinghamshire. Make sure to check out our installation services for garden rooms or garden kitchens too!
