Why get coffee grounds for your plants?
Research by the Oregon State University concludes that coffee grounds are at least 2 per cent nitrogen by volume! Nitrogen is crucial for providing energy to the bacteria in the soil – this bacteria transforms organic matter into compost that plants can then use for nutrition.
Coffee grounds can be used as a soil conditioner, compost, and fertiliser, but the best thing is that it’s easy to get! Plenty of cafes don’t really know what to do with their used coffee grounds, so they’ll happily give you a bag or two for free.
What plants and soil work well with coffee grounds?
Keep in mind that not all plants will benefit from coffee grounds. Since coffee itself is acidic, it can interfere with the normal pH levels of your soil if applied improperly. This can lead to stunted plant growth, the appearance of invasive plant species, and overall decreased quality of your soil.
Luckily, there are a few ways to avoid this:
- Rinse your coffee grounds before use. Fresh coffee grounds (like the ones you can get from a coarse grind) are acidic, but used coffee grounds are neutral. Rinsing your used coffee grounds can bring them to a safe pH level, which won’t affect the soil.
- Work them into the ground around the soil and not onto the plant. If you’re not sure about the acidity levels of your garden, kneading them or adding them to the soil around the plants works better than just dumping them. This is most effective if you’re using them on indoor plants.
- Use a lot of brown compost if you’re using coffee grounds. Coffee grounds are considered a green compost, so too much of it can cause your garden to take too long to break down organic material. Balancing it out with brown compost can help avoid this problem.
- Check your garden’s acidity levels. Using coffee grounds on a vegetable garden is a good idea – a lot of vegetables are acidic, with the notable exception of tomatoes. Shrubs like roses and small lemon trees also thrive in acidic soil. If you’re not sure, order a testing kit from your nearest horticulturist.
A bit of research and some trial and error are the best ways to make sure you get the most out of your coffee grounds. A good rule of thumb to follow is to only use coffee grounds if your plants have been growing for a while, so that the additional nitrogen doesn’t overwhelm the bacteria.
Other uses for coffee grounds in your garden
Aside from fertiliser and compost, there are some other benefits to using coffee grinds on your garden. A lot of this hasn’t been scientifically tested, but plenty of gardeners swear by these tips, so feel free to give them a try!
- Coffee grounds are good repellents against cats, which often enjoy using gardens as a litter box. This might be because of the caffeine, which cats instinctively stay away from.
- You can also use leftover diluted coffee as fertiliser. You can just dump it in the yard after you’re done with it.
- It can also keep pests like slugs and snails away. The raised acid levels in the soil does funny things to these pests.
- They’re very good for worms. Plenty of vermicomposting enthusiasts (and official researchers) encourage adding coffee grounds to worm beds, as they work closely with the bacteria to break down and convert organic waste into nutrients.
You shouldn’t rely on coffee grounds as a magic ingredient to make your garden flourish. If something seems to be really wrong, try looking for other ways to treat it.
If you’ve never given coffee grounds a try, you can ask a coffee-loving friend or your nearest cafe if they can spare a few grounds. Your garden might just buzz with newfound vigour after you’re done experimenting.
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