My parents are big coffee drinkers and at one point, they had a lot of used coffee grounds which they normally tossed. Today, they add it to their compost bin and fertilize their many citrus trees. However, we were wondering if coffee grounds would be good for their avocado trees as well. So, I did a little research to find out more.
Used coffee grounds are good for avocado plants since they add nitrogen and some acidity, which avocado plants 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 avocado trees, are they also good for the soil? Or can they cause more damage than good? Let’s take a further look.
How Do Coffee Grounds Help Avocado Plants?
Coffee grounds help avocado plants by adding nitrogen, potassium, magnesium, and other nutrients, which are all good for avocado trees. Used coffee grounds can break down easily in the soil and are slightly acidic, which also works well for avocado trees since they prefer acidic soil with a pH of 5-7.
Like most plants, avocado trees need three main nutrients—nitrogen, phosphorus, and potassium (known as NPK). Coffee grounds contain all three of these main nutrients, along with other secondary nutrients such as calcium, magnesium, copper, iron, boron, and zinc.
Additionally, coffee grounds are slightly acidic with a pH of 5.5-6.8, which is pretty much perfect for avocado plants since they prefer a soil pH of 5-7. 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 avocado plants.
Generally, when you add fertilizer or soil amendments like coffee grounds, it’s a good idea to periodically check the soil’s pH to make sure it’s still balanced. Two common ways to do this are either with pH strips or with a pH meter. If you’d like a recommendation on a pH meter, you can check out my recommended tools page.
Still, there are some concerns that coffee grounds can hurt avocado plants and the soil. Let’s take a closer look into this.
Will Coffee Grounds Hurt Avocado Plants?
It’s no secret that there is plenty of caffeine in coffee grounds, but the question is whether it’s enough to harm beneficial soil bacteria, insects (like pollinators), and the avocado tree itself.
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.
So, while the majority of the caffeine is lost through brewing, using too many coffee grounds can cause issues with soil life. Since plants thrive on rich and lively soil, this can indirectly affect the plants as well.
However, it really is difficult to use too many coffee grounds on your plants. If you’re not a big coffee drinker and don’t have many used coffee grounds, you shouldn’t need to worry too much.
To be safe, you can always consider composting the coffee grounds to get rid of the caffeine before applying it to your plants and soil.
How To Apply Coffee Grounds as an Avocado Plant 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 2 cups, 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.
We’re still learning that healthy soil means healthy plants, so we should avoid disturbing soil life when possible.
There are three primary ways to apply coffee grounds to your avocado plants.
- Apply it directly
- Mix it with mulch
- Compost it
Again, spreading coffee grounds directly onto your avocado’s tree soil works well if you have a small amount of them, but what’s the best way to apply larger amounts of coffee grounds (above 2 cups per day)?
For a higher volume of coffee grounds, consider either mixing it with mulch or composting it. Aside from having a higher concentration of caffeine and nutrients, too many coffee grounds can stick together and block the moisture in the soil. They can also become moldy and pose issues for plants. Mulching or composting the coffee grounds first can help prevent these issues from happening.
If you’re mulching, some good mulches to consider for avocado trees are leaves, bark, or pine needles.
Whichever method you choose, remember to not let the coffee grounds or compost touch the avocado tree directly. This can potentially chemically burn the plant with excess nutrients or introduce mold and disease. A good rule is to keep any mulch or compost at least 3 inches from the stem or trunk.
How Many Coffee Grounds Should You Use on Avocado Plants?
Generally, try to keep the used coffee grounds below 15-20% of your total soil or compost content. For an occasional espresso brick, you can apply this directly. For the daily pot, considering composting it first. Using too much on your avocado 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 avocado plants. Again, avoid touching the compost to the tree by leaving a space of about 3 inches.
While it’s hard to overdo the coffee grounds, it is possible. Make sure to check your avocado trees every week or so for any issues with their growth, including mold or disease. You can tell if you’re using too many coffee grounds when the avocado 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 avocado trees), they’re more likely to use the coffee ground nutrients faster than just a single avocado tree. In this case, you can apply more than usual.
When Should You Apply Coffee Grounds to Your Avocado Plants?
Avocados are tropical fruits, which means they have a year-round growing season. Because of this, and that coffee grounds decompose quickly in the soil, you can apply coffee grounds at any time of year. However, the most optimal time is right before they have a growth spurt, which is usually in early spring.
There really isn’t a wrong time to use coffee grounds for your avocado trees.
However, if you don’t live in a tropical climate, and are growing avocado trees, consider composting the coffee grounds throughout the year and applying it in 1-2 inch layers in the early spring (after the last frost).
So, while we already found that coffee grounds are good for citrus trees, we recently found that they’re also good for avocado trees, at least in moderation. Too many coffee grounds can lead to caffeine buildup and soil that’s too moist—which can cause yellow or drooping leaves.
Coffee grounds bring a wide range of nutrients and promote rich soil. Aside from the plant benefiting from the nutrients in the rich soil, it can also increase water retention greatly (which is great since avocado trees need A LOT of water). In fact, each 1% increase in the richness of the soil can help the soil hold 20,000 gallons more per acre.
This makes coffee grounds a great investment and amendment for your avocado tree’s soil.
Lastly, remember to check your avocado plant’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.