One really cool houseplant trend I love seeing is people opting for “natural” fertilizers to keep their plants well-fed. It’s good for the plant and the planet! One of the more common natural fertilizers people ask about is coffee grounds applied to the soil’s surface. ZZ Plants (Zamioculcas zamiifolia) only require a handful of feedings each season. But does mulching the plant with coffee grounds make a good natural fertilizer substitute for conventional feed?
Do ZZ Plants like coffee grounds? Although there are certain instances where coffee grounds can be used beneficially to feed your ZZ Plant, adding grounds directly to the top of the soil is not one. This will end up increasing water retention and potentially cause root and rhizome rot.
As I said, there are some benefits to using coffee grounds to feed your houseplants, but to utilize them, you have to understand the proper way they should be applied. Read on to learn the benefits of coffee grounds and how to implement them into your fertilizing strategy. I’ll also discuss some other natural feed alternatives that you can try.
Why Coffee Grounds Make Good Fertilizer
If you spend even a little time researching the benefits of coffee grounds as a fertilizer for plants, you quickly find strong opinions for and against them. While it’s true that there are a lot of incorrect ways to incorporate coffee grounds into your plant feedings, there is no denying that coffee grounds do have some properties that are beneficial to plants.
First and foremost, coffee grounds are made up of organic material. When applied correctly, they can help with the soil structure and can act like sand, in that it helps keep the soil draining properly.
Second, coffee grounds are typically nutrient-rich. They tend to have high concentrations of nitrogen (which most plants love) and contain things like magnesium, calcium, potassium, and other trace minerals, all of which benefit the plant in some way.
So, coffee grounds certainly contain beneficial substances that plants like in a fertilizer, but there are a few things to watch out for.
A Common Mistake When Using Coffee Grounds as Fertilizer
You might have noticed that when I discussed the benefits of coffee grounds, I added in the disclaimer, “when applied correctly.” Turns out, you can do a plant a lot of damage if you don’t understand the best ways to implement the use of coffee grounds as fertilizer.
The most common mistake people make is to assume coffee grounds are a ready-to-go feed for their houseplants straight from the coffee pot. They will add the grounds thickly to the top of the potting soil around the plant, water it in, and hope for the best.
In reality, what is actually happening is that they just created a superfine mulch that prevents water from evaporating off the top of the soil. This increases the water saturation in the soil and creates an environment for rot and fungus to attack the root system of the plant.
In the case of a ZZ Plant, which typically prefers well-drained soil, the additional water retention in the soil can cause root rot. Root rot will stunt the plant’s growth and can potentially kill it.
ZZ rhizomes are also susceptible to improper mulching with coffee grounds. It is often normal to find a ZZ Plant potted with its rhizome poking out of the soil a little bit. This is the preferred way ZZs like to be planted, as it protects the stems from soggy soil.
However, when coffee grounds are piled on the top of the soil surface, the rhizomes tend to get covered up, and again, a wet environment is created around the rhizome and stem, which can lead to both rotting away.
For a ZZ Plant, any soil additive should be carefully incorporated into its existing soil, while making sure water can drain easily, and the soil can still dry out sufficiently between watering.
Composting is King
To truly unlock the benefits of coffee grounds, add them to your compost pile. First and foremost, this will help solve the problem of your coffee grounds being too fine and creating a moisture trap when applied to your potting soil.
Second, while it’s true that coffee grounds are comprised of things seemingly beneficial to plants, some attributes can end up doing additional damage. However, by composting the grounds first, you can help mitigate those adverse effects.
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For example, coffee, and therefore the plant it comes from, contains caffeine. It evolved as a defense mechanism, in that many plants that don’t produce caffeine are actually poisoned by it. The coffee plant drops some leaves, caffeine then seeps into the surrounding soil, and any neighboring plants die off, leaving the coffee plant with plenty of space to spread out.
When we make our morning coffee, we extract as much flavor and caffeine from the grounds as we can, so that we can get our buzz on and tolerate “morning people.” However, even though we extract a lot of caffeine by brewing, it is still present in the coffee grounds when we’re done with them.
This can cause a problem when we use these spent grounds as fertilizer for our houseplants, as the caffeine can seep into the soil and cause the plant harm. By composting the grounds first, you are actually giving them plenty of time to break down with other organic material and for the caffeine to flush out to, hopefully, non-harmful levels.
Coffee grounds are considered “green material” in regards to compost, meaning they contain a higher concentration of nitrogen. So, when adding them into your heap, you’ll also want to add plenty of “brown material” (dry leaves, small sticks, and bark) at a ratio of 4:1 to ensure a good mixture.
This keeps the compost lighter and less wet, which will help with decomposition and make your finished product drain well. Also, it helps combat the antibacterial properties of coffee grounds, which, when added in too high of a concentration, can be detrimental to the good bacteria that are actually doing all the work of breaking your compost down into a usable product.
If you want to incorporate your finished compost into your ZZ Plant soil, the best time to do this would be when you are repotting or dividing your plant. As you prepare your potting soil for your ZZ plant, add about 1 part of compost to 3 parts potting soil.
If you are taking the extra step of adding cactus mix or perlite to lighten your soil up, adjust that amount depending on how dense your finished compost is.
Watering with Leftover Coffee
I’m sure most of us have caught ourselves swirling the dregs of our coffee in the bottom of the mug and then dumping the remainder into the nearest potted plant. I’ll be honest…I’ve done it more than once. However, when you stop to think about it, is it actually OK for the plant?
Typically, a cup of brewed coffee is mostly comprised of water with small amounts of caffeine and other compounds mixed in, some beneficial to plants. I’ve already told you about the dangers of caffeine to a plant, but at such a diluted amount, the occasional splash of coffee isn’t going to affect your houseplant too much.
However, it’s worth being aware that doing this too often can be upsetting to the plant, especially if you like your coffee particularly strong. A good practice is to dilute the coffee by filling your mug the rest of the way with plain water before dumping it into a plant.
Also, do not dump hot coffee on any plant. Most likely, you’ll literally burn their roots, and the plant can suffer as a result.
Other Options for Naturally Fertilizing Your ZZ Plant
As you can see, your ZZ Plant will absolutely tolerate you utilizing coffee grounds as a natural fertilizer, if done correctly. However, if the pitfalls of coffee grounds frighten you, or if you don’t have the space, time, or will to compost them first, you do have other options for natural fertilizers that your ZZ Plant will love.
What is “Well-Balanced Fertilizer”?
When considering what your ZZ Plant needs in terms of nutrients, almost every article (including mine) will tell you to feed it with a “well-balanced fertilizer.” But what exactly does that mean?
What that term typically refers to is the nutrient breakdown within the fertilizer, specifically the nitrogen, phosphorus, and potassium levels (or N-P-K). When referring to a well-balanced formula, basically, you just want to make sure that those numbers are fairly even.
Nitrogen is the nutrient that promotes leafy, green growth on the plant (think stems and leaves). Phosphorus is essential to creating healthy root structures and encourages flower blooms. Potassium helps the plant with things like growth, protein production, and disease resistance.
You’ll see fertilizer formulas with different levels of each nutrient, depending on what it is trying to accomplish. For example, many grass feeds are mainly nitrogen. Commercial “blooming” mixes for annuals and edibles typically punch up the phosphorus to encourage more flowers.
In the case of a ZZ Plant, which has a lot of leafy green growth and a root system easily upset by improper watering, we opt for a balanced mix. We want to make sure all aspects of the plant are benefiting from the feed we provide it.
Store-Bought Organic Fertilizer
One of the most convenient natural fertilizers to use is an organic fertilizer that you can buy at your local garden center. Most places carry a range of different brands, all with their own unique formula, but all accomplish the same thing.
As opposed to chemical fertilizers, which typically possess highly concentrated forms of nitrogen, phosphorus, and potassium made from synthetic substances, organic feeds rely on naturally occurring sources of these nutrients to create their formula.
You will often find things like alfalfa meal, fish emulsion, bone meal, rock phosphate, and kelp meal on the ingredient list, all of which are natural sources of the different nutrients required for excellent plant growth.
One big difference between chemical and organic feeds is the concentration. Because chemical fertilizers use synthetic versions of these nutrients, they deliver them in abundance for the plant to utilize quickly.
Organic fertilizers are usually less concentrated, so feeding more often may be required to achieve the same results. However, the added benefits are that you are eliminating synthetic chemicals from your plants, and you are much less likely to overfeed a houseplant and cause it stress.
Seeing as your ZZ doesn’t need much fertilizer, a store-bought organic feed is a great option to give it what it requires without overwhelming it.
Homemade Feed Options
If you really liked the idea of utilizing your spent coffee grounds as feed, but don’t have it in you to start composting, other homemade options can act as effective fertilizers for your ZZ Plant.
Compost Tea
So, you’ve written off composting for yourself, but you have a friend who loves to do it. If you can convince them to give you a small bucket of it, you’re halfway to making compost tea.
Essentially, all you are doing is seeping the compost in water to make a “tea” that can be used to feed your plants. As the compost steeps, nutrients, minerals, and other trace elements get diluted into the water, leaving you with a rich, brown broth that you can water directly into your plant’s soil.
To make, fill a five-gallon bucket about halfway with water. Dump in about 2-4 cups of compost (either natural or an organic brand you picked up at the garden center) and stir. You don’t want the mixture to get too “soupy” because it’ll be hard to strain. Let the mixture sit up to 48 hours, stirring a few times a day, and then strain, reserving the water.
If you like to experiment, you can add a tablespoon of kelp or fish fertilizer, Epsom salt, or other natural additives to increase your tea’s potency. In most cases, you can water your ZZ Plant with the compost tea as is, but if you are nervous about its strength, dilute it by half with plain water.
Seaweed Tea
Similar to compost tea, you can steep a nutritious mixture using seaweed or kelp. Granted, this might be a slightly smellier approach, but the benefits of a good seaweed tea are worth it! Not only is seaweed an excellent all-purpose fertilizer in general, it also contains a compound called mannitol, which helps increase the plant’s ability to absorb nutrients from the soil.
If you want to make seaweed tea, the best approach is to use dried seaweed. Store-bought is easiest to find (unless you want to go through the added steps of going to the beach and collecting it yourself), but try to find a product that is just “dried” and not “roasted,” as it will be more nutritious for your plants.
Combine about 2-3 cups of dried seaweed with enough water in a blender and process until the seaweed is broken down into small pieces. Pour the mixture into a container and add a half-gallon of water. Let steep for 5-10 hours or longer, as long as the mixture still smells good. It should smell like the ocean. Strain with a fine-mesh strainer and collect the seaweed water in a bowl. Dilute with equal parts of plain water.
Finished seaweed tea can then be applied to your houseplants as a liquid fertilizer.
Aquarium Water
Another crafty way to give your ZZ a boost during feeding is to utilize the used aquarium water the next time you clean your fish tank. Sounds weird, right? Yes, it does, but if you think about it, your fish are basically swimming in a nutrient-rich broth just waiting to be sucked up by a plant.
Decomposing fish food and, of course, fish poop, which are typically high in nitrogen, get dissolved and distributed evenly throughout the water, thanks to the tank bubbler. If you have water plants or seaweed in your tank, as well, the amount of nutrients will be even higher.
Typically, you can apply aquarium water directly to a plant without diluting it.
Raid the Pantry
When looking for natural additives for your houseplants, your kitchen may have more options than you initially thought. Many everyday pantry staples can be utilized to feed your houseplants.
Blackstrap molasses dissolved in water or another liquid fertilizer adds much-appreciated compounds like carbon, iron, sulfur, magnesium, potassium, and copper to the soil. Ground-up banana peels are an excellent go-to source of potassium. Powdered eggshells are a great source of nitrogen and calcium for healthy plant structures.
This approach is more piecemeal, in that you’ll have to find a combination of items that provide what your plant needs, but if you’re serious about going the natural route, you probably already have almost everything you need to make a well-rounded feed for your ZZ Plant. There are tons of recipes to follow online…just pick one from a source you trust.
Closing Thoughts
When it comes to your ZZ Plant, your options for fertilizers are varied and plenty. I like that people are taking an interest in finding more natural alternatives to sometimes harsh commercial feeds. And, while coffee grounds have their place, there are plenty of alternative feeds you can use to keep your ZZ Plant thriving.
