My parents have a palm tree in their backyard and a LOT of extra coffee grounds, so they were wondering if they can use them to fertilize it. To help them out, I did some research. Here’s what I found.
Used coffee grounds are good for palm trees since they add nitrogen and some acidity, which palm 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 palm trees, how exactly do they help them, and how much coffee grounds should we be using? Let’s take a closer look.
How Do Coffee Grounds Help Palm Trees?
Coffee grounds contain a good amount of nitrogen, phosphorus, magnesium, and copper, all of which are important to maintain a healthy palm tree. They also increase the acidity of the soil, which is helpful for palm trees as they prefer more acidic soil with a pH of 5.5-7.5.
Even though palm trees are technically a grass and not a “tree”, they still require similar nutrients to other plants.
The three main nutrients palm trees (and most other plants) need are nitrogen, phosphorus, and potassium, abbreviated as “NPK”. Fortunately, coffee grounds provide 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 palm trees since they prefer a soil pH of 5.5-7.5. 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 palm trees.
If a soil’s pH is either too acidic or alkaline for the plant, it will be unable to absorb nutrients. Over time, this binding of nutrients can lead to leaves and fruit wilting, yellowing, browning, and dropping.
To help with this, when you add any amendments to the soil (including coffee grounds), it’s a best practice to periodically check the soil’s pH.
The best ways to measure the soil’s pH are either with pH strips or a pH meter. I prefer using a meter since they’re affordable and easy to use. If you’d like to see which pH meter I use and recommend, visit my recommended tools page.
If you do find that your palm tree’s soil pH is too acidic, consider adding alkaline materials to the soil like biochar, charcoal, or wood ash.
On the other hand, if your palm tree’s soil pH is too alkaline, use acidic amendments such as sand, peat moss, and of course—coffee grounds.
Will Coffee Grounds Hurt Palm Trees?
Some say that coffee grounds contain too much acidity and caffeine to be used on the soil. But does this hold any truth?
Caffeine is a natural defense mechanism made by plants to repel insects. This makes it a naturally occurring 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 mixed on the caffeine left in coffee grounds.
As shown in the section above, due to brewing, used coffee grounds have much less acidity than fresh grounds. Because of this, it would be fair to assume used coffee grounds also have much less caffeine than fresh.
However, some sources mention used coffee grounds can still be harmful to plant and soil life.
So, to stay on the safe side, the best solution here would be to compost your coffee grounds and let the caffeine and acidity break down. After some time in the compost pile, the nutrients should be the only things remaining from the coffee grounds.
However, if you’re infrequently applying a small volume of coffee grounds, it’s likely not going to harm the soil.
How To Apply Coffee Grounds as a Palm 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.
Depending on how many coffee grounds you have, and what you prefer, there are a few ways you can use coffee grounds as a palm tree fertilizer:
- Apply it directly
- Mix it with mulch
- Compost it
Generally, you can directly apply a small and infrequent amount of coffee grounds to the top of the palm tree’s soil. Just make sure to spread out the coffee grounds to discourage mold and keep them at least 3 inches away from the plant’s trunk.
However, if you have more than the suggested amounts of coffee grounds above, consider either mixing them with mulch or composting them before applying them to your palm trees.
For example, some good mulches to use for palm trees are straw, bark, leaves, and pine needles. Simply mix your preferred mulch and coffee grounds together and apply in a 1-3 inch layer over the soil (under the drip line or canopy of the plant).
Mulching provides the palm tree with a slow release of nutrients, helps the soil retain water, and protects it from the sun and wind. Combined with compost, mulch also greatly helps the beneficial soil life, such as worms and mycorrhizal fungi.
Remember to keep the coffee grounds and mulch at least 3 inches from the plant’s trunk to avoid any mold from spreading.
How Much Coffee Grounds Should You Use on Palm 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 palm trees or compost pile can create imbalances in nutrients and soil life.
If you’re 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).
If you’re composting the coffee grounds first, allow 2-3 months for them to fully decompose. After, apply the compost in 1-2 inch layers around the palm tree. As mentioned above, avoid touching the compost to the trunk by keeping it at least 3 inches away.
For best results, two weeks after you apply coffee grounds, measure your palm tree’s soil pH and check for any growth issues. This isn’t necessary but it’s recommended if you’re applying large amounts of coffee grounds.
Some signs that you might be applying too many coffee grounds are if your palm tree’s leaves are turning yellow and dropping. This is likely a result of the excess nutrients or moisture.
However, this is highly unlikely unless you’re using WAY more than the above suggested amounts (generally, above 15-20% of the soil’s total volume).
If you do find that you have extra coffee grounds to spare, and are looking to use them on your other plants, consider giving them to the palm tree’s companion plants.
When Should You Apply Coffee Grounds to Your Palm Trees?
The best time to apply coffee grounds to palm trees is in the early spring and throughout the rest of the growing season. Avoid using coffee grounds on palm trees in the winter as the trees typically go more dormant and don’t require many nutrients. Instead, in the winter, add coffee grounds to the compost pile.
If you have a hardy variety of palm tree that goes dormant in the winter, it’s best to avoid applying coffee grounds or fertilizers. If applied, these nutrients will go unused and simply sit in the soil. With enough time, fertilizers with high levels of nutrients (especially nitrogen) can chemically burn the plant’s roots.
However, palm trees generally grow in tropical regions and don’t get heavy frosts. So, if you live in a warmer region that doesn’t get a hard frost, you can apply coffee grounds to its soil any time of year.
Coffee grounds are great for palm trees because they add plenty of nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium, and copper. It also provides acidity to the soil and promotes beneficial soil life.
Just as important, coffee grounds also greatly improve the soil’s richness and water retention. In fact, each 1% increase in the richness of the soil can help it hold 20,000 gallons more per acre.
Keep in mind to check your palm tree’s soil pH every now and then. If you’d like a visual on how to do so, check out the video below by Alberta Urban Garden.