While looking into cherry trees’ viability in Texas, I came across some homemade fertilizers for them. One that caught my eye was coffee grounds. I wasn’t able to find an answer if they were good for cherry trees or not, so I did some more research. So, are coffee grounds good for cherry trees?
Coffee grounds are good for cherry trees since they add nitrogen and acidity to the soil. However, some gardeners are concerned about the level of caffeine in the coffee and if will be harmful to beneficial insects and microbes in the soil. For this reason, it’s best to compost the coffee grounds before using them.
So, while coffee grounds are good for cherry trees, what exactly do they do to help, and can they ever hurt cherry trees? Let’s take a closer look.
How Do Coffee Grounds Help Cherry Trees?
Coffee grounds contain good levels of nitrogen, phosphorus, and magnesium, which are important nutrients to keep cherry trees healthy. Additionally, coffee grounds increase the acidity of the soil slightly. As cherry trees prefer a more acidic soil pH of 6.0-7.2, this makes coffee grounds a good fertilizer to use.
Similar to most plants, cherry trees have three main nutrients: nitrogen, phosphorus, and potassium (commonly abbreviated as “NPK”). But there are also many secondary or trace nutrients that can benefit cherry trees and coffee grounds supply many of these.
Some of the nutrients found in coffee grounds include:
As with most fruiting trees, cherry trees also prefer a slightly acidic soil pH.
Generally, sweet cherry varieties prefer a soil pH of 6.3-7.2 while sour cherries like a pH of 6.0-7.0.
So, what’s the pH of coffee grounds?
Fresh coffee grounds have a pH of 5.5-6.8, while used coffee grounds (ones that have already been brewed) have a pH closer to 6.8. This is because when brewed, the coffee grounds lose a lot of the acid and caffeine through the water.
When using any soil amendments, such as coffee grounds, consider checking the soil’s pH every so often. It’s important to make sure it’s staying balanced and not getting too acidic (or alkaline).
The two common ways to check for soil pH are with pH strips or a pH meter. I personally like using a pH meter since they’re affordable and easy to use. If you’d like a recommendation on a pH meter, you can check out my recommended tools page.
Overall, the pH of coffee grounds matches up nicely with the pH that cherry trees prefer. Still, it’s generally best to give your cherry trees used coffee grounds.
But, can coffee grounds (and their residual caffeine) do anything harmful to the cherry trees?
Do Coffee Grounds Hurt Cherry Trees?
When I was first researching coffee grounds, I heard that excess caffeine can harm the soil’s health, namely—killing beneficial insects and bacteria. So, does this hold any truth?
Caffeine is a chemical that’s created by plants as a defense mechanism to repel harmful insects. This makes it a natural insecticide. While caffeine can kill pesty insects, it can also kill beneficial ones such as pollinators. However, the science regarding the harmful effects of caffeine on insects is still debated.
So, even though coffee grounds can help cherry trees, there are some mentions of it harming the surrounding beneficial life.
In my research, I’ve found that used coffee grounds likely won’t have enough caffeine to do a lot of damage (of course this depends on the amount you’re using). However, if you’d like to take the safe route on this one, consider composting your used coffee grounds first to allow for the caffeine and acidity to decompose further.
How to Apply Coffee Grounds as a Cherry Tree Fertilizer
If you have a handful of coffee grounds, you can apply it directly to the cherry tree’s soil. However, if you brew coffee daily, and have 1 or more cups of used coffee grounds, it can overpower the soil. In this case, consider composting the coffee grounds first to reduce the caffeine and acidity.
When applying the occasional handful of used coffee grounds (think the size of an espresso brick), your cherry tree and its soil shouldn’t be impacted and will benefit from the extra nutrients.
However, if you make regular pots of coffee, which can have an average of 1 cup of used coffee grounds or more, this can become concentrated in the cherry tree’s soil. While it likely won’t do much harm, it’s a good idea to compost these grounds first.
If you don’t have a compost bin, don’t worry—it’s not too complex. You can easily start a cold compost bin by using a spare trash bin or container and adding some kitchen scraps to it (see image below). If you notice that flies, mold, or a smell is starting to develop, simply apply a 1-2 inch layer of dry soil. As you add more food and yard scraps, apply more dry soil as needed.
Additionally, you can start a vermicompost bin to accelerate the decomposition process. Just make sure not to add too many coffee grounds to overpower the worms.
Either way, when applying, make sure to keep the coffee grounds and compost at least 3 inches away from the cherry tree’s trunk. This will help prevent mold and disease from being introduced to the tree.
How Many Coffee Grounds Should You Use on Cherry Trees?
As a general rule, use no more than 15-20% of coffee grounds to the total amount of soil or compost. For the infrequent espresso brick, you can spread it out on top of the cherry tree’s soil. For the daily pot, compost the coffee grounds first. Too many coffee grounds can imbalance nutrients and soil life.
For potted cherry trees, I’d suggest using coffee grounds in the same amount as an espresso brick (about a couple of tablespoons worth). Since potted trees have a limited amount of soil, the coffee grounds can add up quickly and become too concentrated.
Even though it’s difficult to use too many coffee grounds, it’s still a possibility. For this reason, it’s a good idea to check on your cherry tree weekly. Look for any issues with its growth. This includes mold or disease.
For example, a good sign that you’re using too many coffee grounds is if your cherry tree’s leaves begin to turn yellow and fall off.
Remember that coffee grounds are considered a “green” compost, meaning that it’s high in nitrogen. To properly balance your soil or compost, you should also be adding some “brown” materials (those high in carbon), such as leaves or wood chips.
When Should You Apply Coffee Grounds to Your Cherry Trees?
You can add an uncommon espresso brick to your cherry tree at any time of the year. For coffee grounds that are more frequent and larger than 1 cup, add them to a compost pile in the winter. After 2-3 months, in the spring, the coffee grounds should be decomposed and you can apply the compost to the tree’s soil.
The main reason not to add coffee grounds or other soil amendments to cherry trees in the winter is that this is when the trees are more dormant. During this time, cherry trees are focused on conserving energy and really don’t need that many nutrients.
Instead, it’s best to provide your cherry trees with nutrients just before the growing season. This is typically after the last frost, or in the early spring.
Once the coffee grounds have completely decomposed over 2-3 months, you can apply the compost in 1-2 inch layers in the early spring and every 1-2 months during the growing season.
Remember to keep an eye on your cherry tree’s soil pH. This is especially true after using coffee grounds and other soil amendments. For a good visual on how to use a pH meter, check out the video below by Alberta Urban Garden.