I had a few banana trees as a kid growing up in Florida, and I’m thinking about growing them again soon. I also currently give many of our plants used coffee grounds, and was wondering if they’d be good to use on banana trees as well. So, I did some research to find out more. Here’s what I found.

Used coffee grounds are good for banana trees since they add nitrogen and some acidity, which banana 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 banana trees, can they cause any harm, and how many coffee grounds should you use?

How Do Coffee Grounds Help Banana Trees?

coffee grounds on a plate to be used in the garden

Coffee grounds contain a good amount of nitrogen, phosphorus, magnesium, and copper, all of which are important to maintain a healthy banana tree. They also increase the acidity of the soil, which is helpful for banana trees as they prefer more acidic soil with a pH of 5.5-6.5.

As with most plants, banana trees require three main nutrients: nitrogen, phosphorus, and potassium (commonly abbreviated as NPK). Fortunately, coffee grounds contain all three of these 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 banana trees since they prefer a soil pH of 5.5-6.5. However, used coffee grounds generally have less acidity than fresh grounds due to the process of brewing. Used coffee grounds generally have a pH closer to 6.8, which is still great for banana trees.

ph scale couch to homestead

Keep in mind that whenever you’re adding amendments to your plant’s soil, it’s a good idea to periodically check the soil’s pH. If the soil pH falls outside of the preferred range of the plant (becoming either too acidic or too alkaline), the plant will be unable to absorb nutrients from the soil and will start to die.

To help measure the soil’s pH, you can use pH strips or a pH meter. I personally prefer using a meter since they’re affordable and easy to use. To see which pH meter I use on my plants, you can check out my recommended tools page.

Will Coffee Grounds Hurt Banana Trees?

While coffee grounds are helpful for most plants, including banana trees, are there any downsides to using them? In my research, I found that some say yes—there are some potential downsides, and it has to do with the caffeine and acidity levels.

Caffeine is a natural chemical made by plants to repel insects. This makes it a naturally occurring insecticide. Generally, insecticides cause more harm than good since they also kill pollinating insects and beneficial life in the soil. However, the science is mixed on the amount of caffeine left in coffee grounds.

As mentioned in the previous section, used coffee grounds have much less acidity than fresh coffee grounds due to brewing. Because of this, it’s fair to assume that used coffee grounds also have less caffeine than fresh.

However, some sources mention used coffee grounds can still be harmful to plant and soil life.

So, if you’d like to be safe, the best way to use coffee grounds for your banana trees (and the rest of your garden) is to let them compost first. After the coffee grounds sit in the compost pile, the caffeine and acidity should break down over time, leaving just the nutrients.

How To Apply Coffee Grounds as a Banana Tree Fertilizer

If you have a handful of coffee grounds, you can apply it directly onto your plant’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 plant.

There are three primary ways you can use coffee grounds as a banana tree fertilizer:

  • Apply it directly
  • Mix it with mulch
  • Compost it

Applying coffee grounds directly to the soil is easy as you simply place it on top of the soil, under the drip line of the banana tree.

Mixing the coffee grounds with mulch is another method, and you can use many different kinds of mulches on your banana trees such as leaves, bark, pine needles, and straw.

Lastly, composting is one of the safest options to make sure your banana plant (and its soil life) isn’t getting excess caffeine or acidity.

So, which method is best?

Generally, the method you choose depends on how many coffee grounds you’re using.

How Many Coffee Grounds Should You Use on Banana 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 it directly. For the daily pot, considering composting it first. Using an excess with your banana trees or compost pile can create imbalances in nutrients and soil life.

So, for smaller, and infrequent amounts of coffee grounds, it’s safe to apply them directly to the soil. Make sure that the coffee grounds are spread out to a layer no larger than 1 inch high to prevent mold from growing.

For larger or daily applications of coffee grounds, your best bet is to mix them with mulch, or even better—compost them.

If you do compost the coffee grounds, allow 2-3 months for them to fully decompose. After, apply the compost in 1-2 inch layers around your banana trees. 

When applying mulch or compost, check that they’re at least 3 inches away from the banana tree’s trunk to prevent mold or disease from spreading.

If you’re still not sure how many coffee grounds to apply, it’s always a good idea to start with small amounts and work your way up gradually (or you can keep it easy and compost them first). For best results, check your banana trees for any growth issues two weeks after you apply coffee grounds.

As long as your coffee grounds don’t exceed 15-20% of the total soil content, your banana trees (and most other plants) shouldn’t have any issues with growth.

If you do find that you have extra coffee grounds to spare, and are looking to use them on other plants, consider giving them to companion plants for banana plants.

When Should You Apply Coffee Grounds to Your Banana Trees?

The best time to apply coffee grounds to banana trees is in the early spring and throughout the rest of the growing season. Avoid using coffee grounds on banana trees in the winter as they typically go more dormant and don’t require many nutrients. Instead, in the winter, add coffee grounds to the compost pile.

Final Thoughts

As mentioned, coffee grounds add many valuable nutrients to the banana tree’s soil (including both primary and secondary nutrients). Coffee grounds also greatly improve the soil’s richness and water retention. For example, each 1% increase in the richness of the soil can help hold 20,000 gallons more water per acre.

Keep in mind to check your banana tree’s soil pH every now and then. If you’d like a visual on how to do this, check out the video below by Alberta Urban Garden.

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