When it comes to how to best use coffee grounds on your vegetable plants and flowers – there can certainly be a lot of contradicting advice on not only when and where to apply spent grounds – but also whether or not they can be helpful or harmful to plants.
One thing is for certain – the spent grounds from a cup of Joe truly are one of the best natural resources around to help power and even protect vegetable plants, annual flowers and perennial plants. Especially when you consider you can usually get them entirely for free!
Coffee grounds can be useful in so many situations. In addition to using them to power planting holes for vegetables and annual flowers, they are also great for energizing hanging baskets and containers plants too. But the benefits of saving and using coffee grounds don’t stop there.
Used grounds can improve soil, adding structure, organic matter and important minerals and nutrients. They can also be a great addition to your compost pile, helping to heat it up and speed decomposition. In fact, it’s actually incredible just how amazing they are!
The Truth About Coffee Grounds & Plants
Let’s first cover the topic of acidity. Coffee grounds often get a bad rap as being acidic. The fact is, spent grounds (not fresh) are almost near neutral when it comes to pH.
Never use fresh coffee grounds for powering plants or soil. Fresh coffee contains a higher acidity level, whereas used grounds have been rinsed and steamed via the coffee-making process. This allows them to lose nearly all of their acid, making them great for vegetable plants and flowers.
What Makes Coffee Grounds So Valuable?
So what exactly makes coffee grounds so amazing as a soil and plant booster? First and foremost, they are an excellent, slow-release source of nitrogen. And nitrogen is a key component in helping to fuel growth in vegetable plants, herbs, perennials and annuals.
Spent grounds contain about 2% of their volume in nitrogen. But they also contain trace amounts of other important nutrients for plants. Nutrients such as potassium, phosphorous, calcium, iron and magnesium.
Even better, all of those nutrients are in a form that can easily be absorbed into soil and into the roots of plants in the best way possible – low and slow. When plants get their nutrients slowly, it promotes strong, steady growth, keeping them healthy and more importantly, manageable.
This is what makes low and slow feeders such as coffee grounds, worm castings and compost so valuable. Heavy fertilizers often power plants too quickly. It can result in too much leaf growth and far less blooms, fruit or vegetables.
Strong fertilizers can also cause potted plants and hanging baskets to outgrow their containers way too early in the season. It’s just one more reason using coffee grounds to help power them all makes so much sense!
How Coffee Grounds Make The Soil Better
Above and beyond their nutritional value to plants, when you use coffee grounds you can also add a tremendous amount of organic matter to the soil. Matter that creates better soil by both adding humus and helping to loosen it to allow water and air to get to the roots.
Adding spent grounds to the soil results in better drainage, aeration and increased water retention for the plants growing in that soil. And not just garden plants, but the flowers that grow in flowerbeds and container soil too.
We also use coffee grounds when making our homemade potting soil. It not only make the soil far more fertile by adding valuable trace nutrients – it also helps the soil retain moisture for the roots of our plants more easily. See our article: How To Make The Best Homemade Potting Soil – With Just 5 Simple Ingredients!
Now let’s take a look at some other great ways to use those coffee grounds to grow better!
Using Grounds In The Garden
We use coffee grounds in a whole slew of ways in our vegetable garden. For starters, when we plant in early spring, we add a few tablespoons of grounds (along with worm castings, crushed egg shells and compost) to every planting hole.
This little concoction helps provide a source of low and slow nutrients directly to the plants as they grow. In addition to putting grounds in the planting hole, we also put coffee grounds on the soil surface around plants.
This serves two great purposes. First, it provides a slow-release of nutrients every time it rains or you water. The nutrients leach through the soil from the moisture above, helping to provide power to the plants via their roots. But the coffee grounds on the surface also help to repel slugs as well.
Slugs delicate skins are easily cut as they crawl across the sharp edges of the grounds. By placing them around the main stalk of a plant, it helps provide a ring of protection. In the process, it can help keep plants safe and power them at the same time!
Listen In Below To Our Podcast On Coffee Grounds
Using Coffee Grounds For Hanging Baskets & Container Plants
Coffee grounds are also an excellent slow-release fertilizer for planters and hanging baskets. They have long been a secret ingredient in our container plants to keep them growing strong and steady with big flower power all season long.
Along with our other favorite natural fertilizer, worm castings, we add a few tablespoons of grounds to all of our pots and containers every few weeks. It’s easy to do! We just sprinkle the grounds on the surface of the soil of each container or basket. Affiliate Link: 100% Pure Organic Worm Castings Fertilizer
When the plants are watered, the magic happens. The nutrients from the coffee grounds and castings slowly leach into the soil. As they do, the plant’s roots soak them up, powering them in that perfect low and slow method.
How To Use Grounds In Flowerbeds
Much like with our vegetable plants, we use spent grounds when we plant annuals in our flowerbeds. We place a few tablespoons in each planting hole to help power the plants. The grounds also help to build the soil up in our flowerbeds with each passing year.
In addition to the trace nutrients the spent grounds provide, they add all important structure and humus into the soil too. In addition, coffee grounds can also be added around the base of each plant as a slow release fertilizer, just as with garden and container plants.
Again, every time you water or it rains, those nutrients on top will flow down into the soil. Just as in the vegetable garden, grounds around the stems of plants will also help protect against slugs.
How To Use Grounds On Perennials, Shrubs, Trees – And Your Compost Pile Too!
Coffee grounds can be used when planting perennials, shrubs and bushes, or added to the soil around those growing throughout the year.
Adding a few tablespoons when planting perennials helps add nutrients and soil structure for long-term growth. For larger bushes or shrubs, we simply add a few coffee filters and grounds all at once around the planting hole. Most all filters are bio-degradable. They help to add even more organic material to the soil as they break down.
Finally, coffee grounds and filters are always a good addition to your compost pile. They are an excellent “green source” to place into your pile. As a green source, coffee grounds help to heat up your pile fast. That means quicker decomposition – and a faster path to more compost.
Here is using coffee grounds on your plants this year! Happy Gardening – Jim & Mary.
Old World Garden Farm
Jim and Mary Competti have been writing gardening, DIY and recipe articles and books for over 15 years from their 46 acre Ohio farm. The two are frequent speakers on all things gardening and love to travel in their spare time.
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