Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden. More on Tony O’Neill
Who doesn’t love coffee?
It gives you a jump start every morning, keeps you fresh during the day, and tastes like heaven. A lot of people use used coffee grounds in the garden.
So are coffee grounds good for vegetable gardens? The answer is yes; they are a fantastic ingredient to use in your garden; they improve soil structure, can feed your plants, and deter some pest species.
You may not know that your garden loves coffee as much as you do. We throw away the spent grounds every morning after making coffee, but why do that if we can put it to use better? The leftover of our morning elixir, AKA coffee ground, is rich in nutrients and compounds essential for the growth of plants.
As a side benefit, using grounds in your garden means recycling organic materials. With every ounce you put in the garbage disposal, a bucket load of essential nutrients goes to waste, which can otherwise be utilized in the garden.
You must’ve heard myths about people who use coffee with their vegetable plants, both positive and negative. Today, let’s examine how coffee can make or break your precious vegetable garden.
How do coffee grounds help the veggies in your garden?
Coffee grounds contain essential nutrients like protein, nitrogen, fatty acids, and oils. They’re commonly used as either fertilizer or in compost. Instead of throwing the coffee grounds and filter into the trash pile, put them into the compost bin.
Add a few other organic materials like leaves, mulch, and a dash of soil, and you’ve got yourself the perfect hummus. Coffee grounds are considered brown compost material (carbon-rich), so add some green compost material (high in nitrogen) to maintain balance.
Coffee grounds restore key nutrients like copper, magnesium, phosphorous, and potassium into the garden soil. Nitrogen is also released during the decomposition process. The coffee ground also encourages the growth of microorganisms that live in the soil, attracts worms into the garden, and is said to repel snails, ants, and slugs.
As opposed to a common misconception, grounds aren’t exactly a substitute for nitrogen fertilizers, as they contain only about 2% of nitrogen. Ensure that your pets, specifically cats and dogs, stay away from it, as caffeine can be fatal to these innocent souls.
The coffee grounds’ acidity or pH value is affected by several factors—for instance, roasting duration, brewing method, and fineness of the ground. Most coffee varieties have an average pH value from 4.85 to 5.10, i.e., acidic.
After brewing, the spent coffee ground usually maintains a pH of about 6.5 (neutral). The pH value also varies according to whether the coffee was cold-brewed or hot-brewed. The acids in the fresh coffee grounds can benefit acid-loving vegetables like radishes and tomatoes.
It’s said to have a disastrous effect on plants (especially new plants) if put directly upon them. The growth issue may happen due to the caffeine in the coffee, but how much caffeine is present in the used grounds is debatable.
Please don’t put them directly upon the seeds or seedlings to avoid problems. Preferably, use it in a compost form as the components have already decomposed and become the perfect healthy and nutritious soil.
Let’s put Coffee Grounds in the Garden.
Taking an improper dosage of the right medicine can be almost as dangerous as taking the wrong medication altogether. In the same way, before using coffee grounds with your precious vegetables, ensure you know how exactly it works. Some plants can’t withstand the high acid concentration in the fresh coffee ground, and some love it.
Coffee grounds can be used as mulch, a cheap and effective way to improve soil richness. Our pets and common pests don’t share our fondness for the strong aroma of coffee. It’s a much-abundant compound you can find almost anywhere in the world. Even if you’re not a caffeine drunk, any local coffee shop will happily share their leftovers for free.
Coffee Ground in Composts:
Coffee grounds contribute several essential nutrients to the compost. You can use either spent or fresh coffee grounds in compost. The used ground is much more common due to its neutral pH level. All components present in the compost have decomposed and turned into soil. So, you get the perks of every material without the drawbacks.
1. Add the Black, Brown, and Green:
To make the perfect compost, use one-third of the coffee grounds, one-third of the grass or fruit/ vegetable peelings, and one-third of mulch (dried leaves or grass). You can also use coffee filters as a substitute for mulch.
Throw in a handful of soil to heat the compost and ensure it doesn’t lack good bacteria. The use of coffee grounds also attracts worms to the compost bin.
The worms eat the compost material, and their waste matter is a proficient soil fertilizer. The black, brown, and green components contribute an important nutrient. In the batch, the harmful effects of each element are neutralized before use.
2. Mix it thoroughly:
Mix the substance thoroughly in a bin using a pitchfork or garden fork. Your ideal pile must be around 4 to 6 feet tall, as small compost piles don’t heat up easily. Mixing the pile once at the beginning isn’t enough. Turn the pile over and around to get the perfect result.
3. Let the compost age:
Organic matters in the compost need some time to rot and decompose before we can use it. Leave it for about three months or more until it looks soil-like. The time duration will vary according to the components used and your environment. Ensure your compost pile is adequately heated to decompose faster and reach its full potential.
4. Spread out the compost:
When the compost has taken a soil-like appearance, spread about 5-6 inches on the vegetable bed every year or twice a year. Use a garden fork or shovel to apply and work it thoroughly throughout the garden. If you lack enough compost, spread everything over the vegetable beds.
Coffee Ground as Fertilizer:
If you don’t have enough time to let the compost age, add it directly to the vegetable bed. It’s not recommended, and composting grounds is a much better idea for your garden soil. You must remember that the soil won’t be enriched with nitrogen overnight.
It’s a long process and requires time and patience. A common misconception about coffee grounds is that it’s acidic. Fresh coffee grounds are acidic, which is neutralized once brewed. To use coffee grounds as fertilizers,
- Spread a thin layer on the garden bed, almost an inch or half of the coffee ground. Ensure the layer isn’t too thick to block air and water from the roots.
- Add nitrogen fertilizer as per the package direction to speed up the process. Remember that coffee ground supplements nitrogen to the soil but is not a substitute for nitrogen fertilizer.
- Mix the coffee ground and nitrogen fertilizer and spread almost 4 inches of mulch. The mulch can be any organic material, including moss, grass clippings, leaves, or pine. This will help them decompose and release nitrogen efficiently. You can also use coffee filters as part of the mulch.
Coffee Grounds for Indoor Plants:
Putting coffee grounds directly upon the indoor plants isn’t a good idea. A thick top layer will become a barrier and retain water leading to fungal overgrowth. It’s best to use compost because it has the perfect nutrient ratio and zero drawbacks. If you still want to try using the grounds directly, then maintain at least a 1:6 coffee-to-mulch ratio.
Other uses of Coffee Grounds in a Garden:
The magic of coffee grounds doesn’t end with fertilizer or a boost to the garden soil. As we spoke earlier, the fresh coffee ground is acidic and brewed or used coffee ground isn’t. Therefore, the new ground cannot be used in various circumstances. Let’s look at some common uses of coffee grounds in the garden.
1. A Substitute for Mulch:
Mulch is an important part of the compost and isn’t abundant enough to come by cheaply. Used coffee grounds can be a perfect substitute for that, as they’re easier to acquire.
Almost every household loves coffee, and we can store the used grounds and the filter. Even your local coffee shop will be more than happy to give you the used grounds if you turn up with a bucket at the end of the day.
2. Keep the Pests Away:
Many gardeners advise spreading coffee grounds around plant beds that repel common garden pests like slugs or snails. Vegetable plants are always vulnerable to insects, and coffee is natural pest control.
Commercial chemical pesticides do the job, but using chemicals with vegetables doesn’t sound healthy, especially when you have a cheap, abundant, and healthy alternative.
3. Coffee Grounds, Dogs, and Cats:
If you’re a pet lover and a gardener, then BEWARE leaving coffee grounds in the garden! Cats and dogs are naturally curious and love to dig around the garden and eat anything that smells good. The strong odor of coffee is inviting, but its caffeine is rather harmful to the little beasts.
A moderate amount of coffee can even cause death to small cats and dogs. An alternate would be a chemical or mechanical solution, but it’s too costly, and coffee trumps it. To overcome the issue, use compost instead of using it as a fertilizer.
If you insist on using coffee in the garden, cover it properly with mulch and take special care that it doesn’t get into the paws or fur of your cat or dog a trip to the vet.
4. Food for your Worm Bin:
Worms are gardeners’ best friends, especially Earthworms. They help decompose organic matter and increase the air and water that gets into the soil. Worms love coffee as the gritty texture of coffee grounds aid their digestive system.
They eat and leave behind castings that work as fertilizers in the compost. Without much ado, treat your slimy friends with the remains of your morning coffee and keep it coming.
5. Acid-loving Vegetable Plants:
Most vegetables grow well in soil with pH values between 6.5 to 7, i.e., neutral. Some plants, specifically root vegetables, prefer acidic soil. The lower pH value helps them absorb the essential nutrients to flourish. Fresh coffee grounds are recommended with carrots, cauliflower, celery, cucumbers, garlic, pumpkin, and tomatoes.
6. Weeds and Allelopathy in Plants:
Gardeners hate weeds, period!
They discourage the growth of plants and make your garden look like a waste bin. The coffee grounds’ allelopathic properties (ability to reduce competition) make them a natural weed killer. They prevent the growth of weeds due to the caffeine and maintain a high temperature. It’s important to use grounds in a moderate amount to avoid growth issues in other plants.
7. Suppress Disease in Plants:
The fungal disease can destroy the whole garden before you even realize it. One way to slow down the process is through companion gardening, but coffee grounds can stop several fungal diseases. As they decompose, coffee grounds have been shown to suppress common fungal infections like Fusarium, Pythium, and Sclerotinia.
Which Vegetable Plants Like Coffee Grounds:
Before putting coffee into your vegetable bed, remember the simple rule. Not every plant loves coffee; we mean fresh coffee because used coffee grounds aren’t acidic. Root vegetables like radishes, carrots, and potatoes favor nitrogen-rich soil.
Fresh grounds are also recommended with cauliflower, celery, cucumbers, garlic, pumpkin, and tomatoes. Speaking of, It can be excellent for germinating sugar beet seeds, cabbage, and soya beans. These plants also require a high nitrogen content during germination.
Which Vegetable Plants Don’t Like Coffee Grounds:
Coffee grounds hold a treasure trove of nutrients, including Nitrogen, Phosphorous, and Potassium. Used (and dried) coffee grounds can be laid out in the vegetable garden covered with mulch. The best way to use grounds is compost as the individual material has decomposed, and the nutrients are ready for the soil.
Using Fresh Coffee Grounds v/s Used Coffee Grounds:
Fresh Coffee Grounds:
- You can spread fresh coffee grounds in acid-loving vegetable beds. Root crops like radishes and carrots favor acidic soil, especially when planting.
- Fresh coffee grounds are said to suppress the growth of weeds in the garden.
- Only a few plants can withstand or require a high concentration of acid.
Used Coffee Ground:
- Brewed coffee grounds have a pH level of almost 6.5, which is neutral.
- It can be used as a composite or fertilizer with nearly any vegetable plant.
- The smell of coffee repels pests and attracts worms into the garden.
FAQs on Are coffee grounds good for vegetable gardens?
Can you put too many coffee grounds in your garden?
Excessive use of anything never leads to success. As coffee grounds, specifically fresh ones, are acidic, they can be an issue. Using them with acid-loving plants like camellias and azaleas can improve its tilth, but too much coffee can halt the growth of other plants in the garden.
Are Coffee grounds good for tomato plants?
Tomato plants favor a high nitrogen component which in turn means acidic soil. Be careful with the fresh coffee grounds as tomatoes like slightly acidic soil, and overly acidic soil may backfire.
Where do I get the coffee grounds from?
Coffee ground is an important part of our daily life. But if you’re not a coffee lover or need more grounds, try your local coffee shop. A little kindness goes a long way, buy a cup of coffee and ask if they’ll give you the spent coffee grounds at the end of the day.
Starbucks is also a place to go as they’re known to give away the spent grounds to anyone for free. It’s a win for both concerned parties, you’ll get the grounds, and they can put their waste to use better.
Coffee grounds are a brilliant ingredient for the garden; if you can get these, use them as a good nitrogen source for your compost.
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Remember, folks, you reap what you sow!