It’s no secret that my parents are big coffee drinkers, so we’re often looking for ways to give those coffee grounds a second purpose. One of the best ways we’ve found is to use them in the garden. They have several fruit trees, and while many of them are citrus, they also have fig, avocado, and kumquats. We previously learned that coffee grounds are in fact good for citrus trees, but are they also good for other fruit trees? I did some research to learn more.
Coffee grounds can add nitrogen and acidity to the fruit tree’s soil, but some gardeners are concerned about the excess caffeine. Since caffeine is a natural insecticide and can kill beneficial bacteria and insects, it’s best to let the coffee grounds decompose in a compost pile first before using it on the soil.
So, even though coffee grounds are good for pretty much any fruit tree including apple, cherry, peach, and avocado, how exactly do coffee grounds benefit them? And is there any downside to using coffee grounds?
How Do Coffee Grounds Help Fruit Trees?
Before you apply anything to your garden’s soil, it’s important to first know what benefits they bring. After all, you don’t want to be supplying too much of one nutrient or making the soil too acidic. So, how exactly do coffee grounds help fruit trees?
Coffee grounds have a variety of nutrients including nitrogen, phosphorus, magnesium, and copper. These readily available nutrients are essential to the health of fruit trees. Coffee grounds also raise the soil’s acidity, which is beneficial since most fruit trees prefer a slightly acidic soil pH of 6.0-7.0.
Aside from the primary nutrients above, there are several other secondary nutrients found in coffee grounds such as calcium, iron, and zinc.
Coffee grounds also have an acidic pH of 5.5-6.8, and since most fruit trees like a slightly acidic soil pH of 6.0-7.0, coffee grounds make for a great addition to soil.
However, even though these benefits from this soil amendment sound exciting, it’s also important to consider any potential cons.
Do Coffee Grounds Hurt Fruit Trees?
At the beginning of this article, we briefly touched on the caffeine levels in coffee grounds and how they might harm the beneficial life in the soil. Let’s examine this a bit closer.
Caffeine is a natural chemical that’s created by certain plants as a defensive action against harmful insects. Essentially, caffeine is a naturally occurring insecticide, which can be lethal for beneficial insects such as worms and pollinators. However, used coffee grounds typically don’t have much leftover caffeine.
In short, while unused coffee grounds contain lots of caffeine and a more acidic pH of 5.5-6.8, used coffee grounds typically have much less caffeine and a pH of 6.8. This shows that used coffee grounds have lost most of their caffeine and acidity through the brewing and their leftover nutrients (such as nitrogen) are a great addition to the soil’s health.
So, now that we know that used coffee grounds are good for fruit trees, what’s the best way to apply them and maximize the benefits to the soil?
How to Apply Coffee Grounds As Fruit Tree Fertilizer
For a smaller volume of coffee grounds, such as a brick of espresso, you can apply it directly to the top of the fruit tree’s soil. For the daily pot of coffee, which is more than 1 cup of coffee grounds, consider mulching or composting it first. Composting will help break down the residual caffeine and acidity.
There are three main ways to apply coffee grounds to your fruit tree’s soil. They are:
- Applying it directly
- Mixing it with mulch
- Composting it
Generally, if you have a small volume of coffee grounds, you’re fine using it on the top of the soil. Just remember not to touch the tree’s trunk with it as it can introduce disease. Keeping the grounds at least 3 inches away from the trunk is a good spacing to follow.
Also, spread out the coffee grounds over the soil to avoid them clumping and blocking the soil from absorbing water and air. Clumped and wet coffee grounds can even introduce mold to the soil or the tree.
On the other hand, if you have a larger amount of coffee grounds, consider mixing it with mulch or composting it. You can use mulches such as leaves, bark, or pine needles.
If you’d like to be extra safe, you can always compost the coffee grounds first to leach out the caffeine and acidity before using it on your fruit trees.
How Many Coffee Grounds Should You Use on Fruit Trees?
As a general rule, keep the used coffee grounds under 15-20% of the total amount of soil or compost. While coffee grounds are small in surface area and can decompose quickly, using too many can overpower the soil and negatively affect fruit trees. Soil should still have leaves and other carbon-rich, brown materials.
It’s important to provide balanced soil and compost that includes both brown and green materials.
When it comes to compost, while coffee grounds have a brown color, they’re in fact a green material. This means coffee grounds are high in nitrogen and need to be balanced with carbon-rich, brown materials such as leaves, bark, and branches.
When applying coffee grounds to potted fruit trees, I’d suggest using a 1-2 inch layer of used coffee grounds on the top of the soil every 1-2 months. Again, avoid touching the coffee grounds to the trunk of the tree. If you’d prefer to compost the grounds first, the same measurement and timeframe still apply.
If you’re concerned that you may be adding too many coffee grounds to your fruit tree’s soil, consider using a soil pH meter to check if the soil is getting too acidic. They’re fairly inexpensive and easy to use. To see which pH meter I recommended, you can check out my recommended tools page.
When Should You Apply Coffee Grounds to Your Fruit Trees?
Coffee grounds can be applied to soil any time of the year. However, keep in mind that some fruit trees such as apples, cherries, and peaches go dormant in the winter and won’t need as many nutrients. Because of this, it’s best to compost the grounds in the fall and then apply the compost in the spring.
Typically, coffee grounds take about 2-3 months to decompose, so if you are adding it to your compost pile, the best time to do it is in the fall. After a few months (and after the last frost), fruit trees will be more active and can benefit more from the extra nutrients.
However, if you’re in a year-round growing climate (such as the tropics) and you’re growing tropical, evergreen fruit trees such as citrus, avocado, and banana, you can apply coffee grounds to your garden at any time.
So, while we previously found that coffee grounds are good for citrus trees, we’ve learned they’re also good for apple trees, stone fruits (cherries, plums, peaches, etc), tropical fruits (mango, banana, avocado, etc), and other fruit trees.
When you’re using your coffee grounds for your fruit trees, remember to keep it to no more than 15-20% of the total soil and keep the grounds/compost at least 3 inches from the trunk of the tree. Used coffee grounds have much less caffeine and acidity than unused, so it’s better if you brew them first. When in doubt, compost the grounds and apply the compost in the spring with a 1-2 inch layer. Happy gardening!