A question I am often asked by new gardeners is: Is it safe to use coffee grounds in my garden? In our caffeine-addicted society, coffee grounds – the ground up powder of coffee beans – are so ubiquitous . Your local cafe produces buckets every day and most households also generate a ready supply from their kitchen.
In recent times, coffee grounds have gotten a bad rap in the media. I recently heard a popular prime time gardening show warn against using them in your worm farm because they are “acidic”. When I first started growing blueberries many years ago, I was given much similar advice – which is that you should use coffee grounds around blueberry plants to create the acidic conditions that they thrive in.
You may also have seen some recent articles showing that using coffee grounds in the soil will stunt the growth of plants. As a result of this, many gardeners now think coffee grounds are toxic in the garden. In fact, many gardeners I talk to tell me that they now put coffee grounds straight into their landfill or green waste bins.
Blueberry bushes are a popular choice for home gardens and orchards, prized for their bursts of sweet, tangy fruit. However, growing plump, flavorful blueberries requires providing bushes with the right soil conditions and nutrients. This leads many gardeners to wonder – do blueberry bushes like coffee grounds?
Coffee grounds have become an increasingly popular soil amendment among gardeners. The grounds are abundant, free, and deliver some key benefits. But using coffee grounds also comes with important considerations. By understanding how to leverage coffee grounds as part of an overall soil health strategy, blueberry growers can help bushes thrive.
An Overview of Blueberry Needs
Before exploring the potential of coffee grounds, it’s important to understand what blueberry bushes require for optimal growth:
-
Acidic Soil – Blueberries thrive in acidic soil, with an ideal pH of 4.5-5.2. This pH helps bushes absorb nutrients effectively.
-
Well-drained soil – Blueberry roots demand oxygen, so drainage is key. Standing water invites root rot.
-
Mulch – Mulch helps acidify soil, retain moisture, and suppress weeds around bushes.
-
Sun – At least 6 hours of daily sunlight fuels growth and fruit production
-
Even moisture – Especially during fruit set and development, consistent moisture is vital.
With basic needs covered, ensuring bushes get sufficient nutrients bolsters plant vigor and yields. This is where amendments like coffee grounds come into play.
The Potential Benefits of Coffee Grounds
Coffee grounds offer blueberry bushes several potential perks:
-
Nitrogen – Coffee grounds contain nitrogen, which promotes vegetative growth like leaves and branches. This provides fuel for fruit production.
-
Other nutrients – Grounds also supply phosphorus, potassium, and micronutrients like copper and magnesium. A balance of nutrients feeds the whole plant.
-
Organic matter – Coffee grounds are composed of organic matter, which improves soil structure and moisture retention.
-
Acidity – The grounds contain organic acids that can help lower pH for blueberry’s preferred acidity.
-
Weed suppression – As a mulch, grounds can block light to prevent weed seed germination and growth.
-
Free and eco-friendly – Coffee grounds are 100% free recycled waste product that promotes sustainability.
With an abundance of nitrogen and acidity, it’s easy to see why coffee grounds seem like an ideal blueberry booster. But there are some important limitations to consider as well.
Using Caution When Adding Coffee Grounds
While promising, coffee grounds do come with some caveats blueberry growers should keep in mind:
-
Overacidifying soil – Grounds can drop pH too low if over-applied, which impairs nutrient availability. Ideal blueberry soil pH is 4.5-5.2.
-
Excess nitrogen – Too much nitrogen from grounds can cause excessive leaf growth rather than fruit production.
-
Nutrient variability – Since grounds come from different sources, their exact nutritional analysis is unknown.
-
Caffeine content – Coffee grounds contain caffeine, which in large doses can potentially inhibit plant growth.
-
Pest attractant – The smell of grounds can lure pests like snails and slugs, which feed on plants.
-
Crusting – If applied heavily, dry grounds can form a crust that blocks water and air from reaching plant roots.
By acknowledging these limitations, growers can use grounds judiciously as part of a multifaceted soil strategy.
Best Practices for Using Coffee Grounds on Blueberries
When leveraged properly, coffee grounds can be a helpful supplement for enriching blueberry plantings. Here are some best practices to follow:
-
Test soil pH – Test current pH so you know if you need to acidify soil. Only add grounds if pH needs lowering.
-
Use sparingly – Apply just a thin 1/4-1/2 inch layer around bushes. Too much overwhelms soil.
-
Mix with compost – Blend grounds with compost so they break down slowly, providing a steady nutrient release.
-
Alternate with other fertilizers – Rotate grounds with balanced organic fertilizers to nourish bushes completely.
-
Topdress – Spread grounds lightly atop soil so they can work into root zones gradually as they decompose.
-
Monitor pH and growth – Note plant and soil responses to gauge if more or less grounds are needed.
-
Use other acidic mulches too – Pine needles, peat moss, and rotted leaves also acidify soil safely for blueberries.
By using coffee grounds thoughtfully as one piece of an integrated soil amendment approach, growers can unlock the potential of this free, eco-friendly booster.
An Effective Soil Health System for Thriving Bushes
While coffee grounds can provide benefits, they work best as part of a multifaceted soil health system. Here are some key strategies to nurture great soil and vigorous bushes:
-
Test soil yearly – Use home soil test kits to monitor pH and nutrient levels so you can customize fertilization.
-
Add organic matter – Rotted manure, compost, peat moss, and leaf mold build soil structure and water holding capacity.
-
Use balanced organic fertilizer – Look for a mix of nitrogen, phosphorus, and potassium tailored to blueberries.
-
Topdress with compost – Spread 1-2 inches of finished compost around bushes each spring to enrich soil.
-
Apply acidic mulch – Mulch with materials like pine straw, leaves, or wood chips to acidify soil.
-
Manage weeds and pests – Keep plantings clear of weeds and use row covers or organic sprays to prevent pest damage.
By proactively building soil health with practices like these, growers give blueberry bushes the foundation they need for an abundant harvest.
While coffee grounds will not meet all of a blueberry bush’s nutritional needs, used strategically they can be a helpful supplement. Grounds provide nitrogen, organic matter, and acidity. But too much risks excessive acidity, nutrients imbalance, and other issues. The key is using grounds in moderation as part of a multifaceted soil amendment approach. By testing soil, adding balanced organic fertilizers, using acidic mulches, and building soil organic matter, growers can unlock the perks of grounds while avoiding potential pitfalls. Leveraging coffee grounds wisely helps create optimal conditions for a thriving, fruitful blueberry harvest.
Are coffee grounds acidic?
Absolutely not. It is a complete myth that coffee grounds are acidic when decomposed. Most things when decomposed tend towards pH neutral.
We add coffee grounds in bulk quantities to our worm farm and regularly test the pH. The pH of our worm castings tests towards neutral or even a little basic (and no we do not add lime to our worm farm). Similarly where we add bulk quantities of coffee to our garden soil, our soil pH is still high – and yes there are other factors at play here. I am not saying coffee causes high soil pH. I’m simply illustrating that in the areas where we’ve added coffee grounds, the soil has not become any more acidic than places where we haven’t. [This is a topic I will be writing about later. If you have stunted plants, chances are your soil pH is wrong and likely too high].
Let me set the record straight.
We’ve been using coffee in our garden for many years. In fact, our entire garden is built on coffee – coffee grounds and coffee husks. We literally use a mountain of coffee in our garden: we get a delivery of 1-2 cubic meters of coffee grounds every year, and our lifeless sandy soil soaks up countless sacks of coffee husks.
No our plants are not suffering because of it – quite the opposite really, they are flourishing. And no our soil is not acidic, if anything our soil suffers with high pH which we need to correct. (Note: the high pH is not due to the coffee, but adding coffee has certainly not helped to acidify our soil to counteract our basic soils).
Let’s look at an example. In the area behind our shed, our soil is dry and grey sandy lifeless soil. In order to improve the soil, we piled on over 10cm of coffee grounds in winter. Just some months later in spring, we were able to grow 4 tomato plants, 6 beans and a pumpkin in this tiny space, with the only soil amendments being coffee grounds, coffee husks and horse manure. Quite a remarkable transformation given that even weeds struggled to grow before.
I am a huge advocate of using coffee to improve your soil. We are both non-coffee drinkers, so quite ironic really that our entire garden is powered by coffee!
- Coffee grounds are an incredibly valuable source of organic matter for your garden. They tick all our boxes for a soil amendment – they are rich in nutrients, widely available and sustainable.
- Coffee grounds bring life back to your soil – if you don’t believe me, put some coffee grounds into your worm farm or on a patch of soil, check back in a week or so and you’ll find it teeming with worms.
- As coffee grounds are so fine in texture, they break down quickly to add nutrients which your plants will lap up.
HOW TO Use Coffee Grounds on Blueberries
FAQ
How to use coffee grounds for blueberry bushes?
Occasionally, scatter your spent coffee grounds on the top of the dirt to wake up your blueberry plants.
Which plants cannot use coffee grounds?
Coffee grounds inhibit the growth of some plants, including geranium, asparagus fern, Chinese mustard and Italian ryegrass.
Can I just sprinkle coffee grounds in my garden?
Yes, you can sprinkle coffee grounds in your garden, but it’s best to mix them into the soil or use them as a mulch, rather than just sprinkling them on top.
What is the best fertilizer for blueberries?
Nutrient Maintenance for Blueberries Blueberry bushes don’t like a lot of nutrients, they do need some nutrients. Lee recommends applying soybean meal, alfalfa meal or cottonseed meal once each year to provide a little organic nitrogen. Two pounds of meal per 100 square feet of bushes is Lee’s preference.
Do blueberry plants need coffee grounds?
Specifically, blueberry plants, which thrive in acidic soil, can significantly benefit from the application of coffee grounds. This article will guide you through understanding the needs of blueberry plants, the benefits of coffee grounds, and how to prepare and apply them to your garden for better growth and berry production.
How to grow blueberry bushes?
This is why testing your soil is the number one blueberry growing tip. If the pH is low, then you shouldn’t add coffee grounds. For one blueberry bush in your garden, one or two cups of leftover coffee grounds should be sufficient. You should sprinkle some evenly on the surface of the soil and then use a trowel or shovel to till them.
Do coffee grounds affect blueberry taste?
The impact of coffee grounds on blueberry taste is still a topic of research. Generally, soil health and nutrient balance are the more significant factors determining the flavor of blueberries. Using coffee grounds as a specific fertilizer is unlikely to result in a pronounced effect on taste.
Can you use coffee grounds to fertilize blueberry bushes?
Discover how to use coffee grounds to fertilize blueberry bushes for lifelong berry production and continued plant health. Mix two cups of old, dry coffee grounds with a gallon of warm water. Use your most convenient watering can for application, and water around the base of the plants.
How do you use coffee grounds on blueberry bushes?
If you have under 2 cups of coffee grounds, apply them directly to your soil by spreading them out in a thin layer. It’s recommended to have a layer no higher than 1/2 an inch and to keep the coffee grounds at least 3 inches from your blueberry bushes terminal stem.
How much coffee grounds should I use per blueberry plant?
A balanced application of about one cup of coffee grounds per blueberry plant every month can maintain suitable pH levels while enriching the soil. Applying coffee grounds to blueberries at the right time enhances growth and fruit quality. Focus on the following factors for optimal results.