Homemade fertilizers and composting are becoming more popular, and many gardeners are looking at ways to recycle nutrients for their apple trees. One of the best ways to do this is with kitchen and yard scraps, and the most common? Coffee grounds. Because of this, I wanted to find out more if coffee grounds are good for apple trees, so I did some research. Here’s what I found.
Used coffee grounds are good for apple trees since they add nitrogen and some acidity, which apple trees prefer. However, there are some concerns about the leftover caffeine in the coffee grounds. Caffeine is a natural pesticide, so some worry about it killing beneficial insects and soil bacteria.
So, while coffee grounds are good for apple trees, can the caffeine and acidity harm the soil? Also, how much should you use, and when? Let’s take a closer look.
How Do Coffee Grounds Help Apple Trees?
Coffee grounds contain a good amount of nitrogen, phosphorus, magnesium, and copper, all of which are important to maintain a healthy plant. They also increase the acidity of the soil, which is helpful for apple trees as they prefer more acidic soil with a pH of 5.8-7.0.
As with most plants, apple trees require three main nutrients: nitrogen, phosphorus, and potassium (abbreviated as NPK). Fortunately, coffee grounds contain all three primary nutrients, along with other secondary nutrients such as calcium, magnesium, copper, iron, boron, and zinc.
Coffee grounds are also slightly acidic with a pH of 5.5-6.8, which is pretty much perfect for apple trees since they prefer a soil pH of 5.8-7.0. However, used coffee grounds generally have less acidity since most of it is lost through brewing. Used coffee grounds generally have a pH closer to 6.8, which is still good for apple trees.
As with any soil amendments, it’s a good idea to periodically check the pH of the soil to make sure it’s still balanced. Two common ways to do this are with pH strips or a pH meter. I personally like using a pH meter since it’s easier. If you’d like a recommendation on a pH meter, you can check out my recommended tools page.
Will Coffee Grounds Hurt Apple Trees?
Some are concerned that the caffeine content (and even the acidity) in coffee grounds can harm beneficial soil bacteria and even some pollinators, but does this hold any truth?
Since caffeine is a natural defense mechanism made by plants to repel insects, it’s essentially a type of insecticide. Generally, insecticides can cause more harm than good since they also kill pollinating insects and beneficial life in the soil. However, the science is debated on the caffeine left in coffee grounds.
As we saw above, the pH of used coffee grounds was significantly less acidic than fresh coffee grounds. The same can be said for the caffeine content. Simply—much of the caffeine gets extracted when brewing. However, if coffee grounds are used in excess, they can harm the soil life, which then affects the plants.
To stay on the safer side, consider composting the coffee grounds instead of applying them directly to the soil—especially if you go through a lot of coffee grounds.
How To Apply Coffee Grounds as an Apple Tree Fertilizer
If you have a handful of coffee grounds, you can apply it directly onto your garden’s soil. But if you have a daily pot of coffee, generally more than 1 cup, consider composting it first to decrease the caffeine. Usually, it takes about 2-3 months for the coffee grounds to decompose and become usable by the tree.
There are three common ways you can use coffee grounds in your garden:
- Apply it directly
- Mix it with mulch
- Compost it
Generally, the method you choose will depend on the number of coffee grounds you use.
For the occasional pot of coffee or espresso brick, you can apply this to the soil directly. For more frequent applications, and those over 1 cup in size, consider mixing it with mulch, or even better—compost it.
If you decide to mulch, some good options for apple trees include leaves, bark, and pine needles. Simply mix the mulch and coffee grounds together and apply in a 1-3 inch layer over your apple tree’s soil. Aside from providing valuable nutrients, the mulch will help the soil retain water and protect it from the sun. Remember to keep the mulch at least 3 inches from the apple tree’s trunk to avoid spreading mold to the tree.
How Many Coffee Grounds Should You Use on Apple Trees?
As a general rule, keep the used coffee grounds below 15-20% of your total soil or compost content. For the occasional espresso brick, you can apply this directly. For the daily pot, considering composting it first. Using too much on your apple tree or compost pile can create imbalances in nutrients and soil life.
If you’re composting the coffee grounds first, wait 2-3 months for them to decompose properly. After, you can apply the compost in 1-2 inch layers around the apple trees. As with the mulch, avoid touching the compost to the tree by applying at least 3 inches from the trunk.
Typically, it’s hard to overdo the coffee grounds, but it is still possible. Because of this, check your apple trees every week or two for any issues with their growth. You can tell if you’re using too many coffee grounds when the apple tree’s leaves turn yellow or start to fall off.
Additionally, if you have a lot of plants in your garden (for example, if you have companion plants alongside your apple trees), they can use the coffee ground nutrients faster than just a single apple tree. In this case, you can apply more than usual.
When Should You Apply Coffee Grounds to Your Apple Trees?
The best time to apply coffee grounds to apple trees is in the early spring and throughout the rest of the growing season. Avoid using coffee grounds on apple trees in the winter as the trees typically go dormant and don’t require many nutrients. Instead, in the winter, add coffee grounds to the compost pile.
In the spring and growing months, you can apply coffee grounds in any of the ways mentioned above.
However, in the winter, it’s best to add the coffee grounds to the compost pile first so the nutrients don’t go unused in the soil. Too many nutrients sitting in the soil can chemically burn the apple tree’s roots and negatively impact the tree’s health.
Coffee grounds provide apple trees with valuable nutrients and promote rich soil. Aside from this, coffee grounds can also greatly increase water retention (which is great since apple trees need quite a bit of water). In fact, each 1% increase in the richness of the soil can help the soil hold 20,000 gallons more per acre.
Keeping more moisture in the soil benefits both the soil life, as well as the tree. For example, some issues such as curling leaves on apple trees can be improved with coffee grounds. For more information on curling leaves, check out my recent post: How to Fix Curling Leaves on Apple Trees.
This makes coffee grounds a great investment and amendment for your apple tree’s soil (just make sure not to use too many).