We love our plant babies and want them to live their best lives. So, it’s common sense to fertilize them, right? Not so fast… it’s not so clearcut! Houseplants live indoors. They typically don’t see as much light (or light in the same way) as their friends out in the wild. Because of this, their growth is limited and they don't need as many nutrients. Plus, without all that light, they typically don’t grow any extra stuff, like fruits and flowers. And fruits and flowers require a lot more nutrients.
Houseplants need three things to thrive: a good potting mix, water, and light. Fertilizer is like an added bonus. You can think of fertilizer like vitamins for your plant—it can help boost nutrition, but it doesn’t replace meals! 😋
Do I Need to Fertilize?
Plants require light to grow. Throwing it back to science class, photosynthesis is the way the plants make their food—it's a metabolic process. It all starts with light—light allows a plant to convert carbon dioxide and water into energy (as in food) and as a byproduct, release oxygen out into the world. So, is your plant ever really “hungry” for anything besides what they need to photosynthesize? Well, yes and no!
If your plant isn’t getting enough light, they're also not photosynthesizing and thus not growing much.
If you want to help your plant to grow, it’s a better idea to move them to better light instead of pumping them up with fertilizer. The extra nutrients won’t do much of anything (but potentially hurt) if they're not getting ✨good light✨.
Also—keep in mind that indoor potting mix is already chock full of the nutrients your houseplant might want. It's different than outdoor gardening soil or the dirt in your backyard. It’s been formulated for indoor life in a container, so it compensates for those very specific factors. Granted, your plant will eventually use up those nutrients. So, fertilizing a plant isn’t a complete “no-no.” It’s more of a “know when to do-so.”
Before we talk about how to fertilize, though, we want to warn you: over-fertilizing is a very real thing. And it can have the opposite effect of what you intended—weakening your plant and leading to damaged roots and yellowing leaves.
If you already have your plant in their optimum lighting condition and have their watering needs down pat, you can break out the fertilizer. A decidedly casual, bordering on lax, approach to fertilizing will do the trick for most houseplants.
Dangers of Over-Fertilizing
Over-fertilizing is a lot easier to do than you’d think, especially in dormant periods (like winter). Just like us humans, when we take in too much of a good thing, it can lead to problems. In particular, the salts in synthetic fertilizer can build-up, along with the nutrients, and cause some serious damage. If you are actively fertilizing your plants, keep an eye out for these common signs of over-fertilization:
- Burned leaves: The edges of your leaves can start looking crispy and brown.
- Layer of fertilizer on soil: The top layer of soil can start looking a little crusty—that’s not a good sign!
- Burned roots: Fertilizer doesn’t just burn the leaves; it can also damage the roots of your plants. They will look start turning black or brown and will be unable to absorb much of anything, let alone those nutrients.
- Wilting, yellowing, or falling leaves: This seems counterintuitive since fertilizer is supposed to help your plant grow, not kill them! Unfortunately, too much fertilizer (and those burned roots) mean the plant is unable to soak up moisture…leading to unhappy leaves.
- Stunted growth: Again, it seems like common sense that fertilizing would promote growth—but that’s not the case if you've gone overboard.
While this list of symptoms can overlap with other issues, if you suspect you got a little trigger happy with the fertilizing and you're certain it's not pests or a watering issue, then you're most likely dealing with a reaction to excess fertilizer.
Oops, I Already Over-Fertilized My Plant!
Are you wondering why you didn’t come across this article as you were dousing your plant with fertilizer a few weeks ago? Are these signs already showing up on your plant?
The bad news: you accidentally smothered your plant with love. The good news: you can take some steps to reverse the damage.
Remove Any Fertilizer Crust
Examine the soil for crusting. If you see a white or yellowish and...frankly, crusty looking layer of soil, carefully remove as much as you can with a hand trowel or other scooping implement (like even a spoon could work). Try not to remove too much soil along with the crust, keep it under a quarter inch or so.
Prune the Plant
Take some time to remove any of the burned, wilted, or yellowing leaves (they won't bounce back from this). And if it's a very severe case, you may want to take a peek at the roots to see if they are burned and starting to rot. You'll have to prune these back as well in hopes of saving your plant. 🙏
Leach, Baby, Leach
It’s time to purge out as much fertilizer as possible. You can give your plants a rinse in the shower, a deep sink, or outside with a hose if the weather is nice.
Before you leach, make sure your plant’s pot has drainage holes! For so many good reasons, but particularly in this case, the water and excess fertilizer has to go somewhere.
To successfully leach, you have to give your plant a good long watering. Let the water drain fully... aaand, repeat. You may have to repeat this up to four times for a full leaching process.
Take a Break from Fertilizing
You’ve smothered the poor thing enough. Let the plant recover. We don’t recommend fertilizing again until the plant is fully recuperated, which could take up to a full season.
Over-fertilizing twice in a row will almost certainly lead to heartbreak.
Be patient, your plant isn’t going to return to normal overnight. It takes time and attention—maybe even a little extra love.
Should I Even Try to Fertilize?
Did we scare you with the dangers of over-fertilizing? Even after going over the doom and gloom of it all, we actually don’t want you to think it's the worst thing you can possibly do for your plant. It can be a good thing! We just want you to internalize that light, water, and potting mix are the real pillars of success for a thriving houseplant. 🏛
With all the scary stuff out of the way, there is a time and place for fertilizer!
When to Use Fertilizer
You can use fertilizer on a happy and healthy plant when they are in their growth period, generally in the spring. You don’t want to use fertilizer while a plant is dormant or recovering from another issue. It will simply waste the fertilizer or potentially exacerbate a problem.
Fertilizer is great for an extra boost when your plant is already thriving.
You’ve got them in the right spot—and they've truly found their light. You’ve also figured out your plant’s watering needs and they're looking oh so lush. But you want your special plant to have the perfect life. So let's review some options.
Types of Fertilizer
You’ve decided you want to fertilize. Now what? Now, you choose what type of fertilizer you want to give your plant. There are many options out there, so we'll help you decide by laying out some pros and cons for each type.
A good houseplant fertilizer should contain a fairly equal amount of these macronutrients:
- Nitrogen (N): Nitrogen helps plants photosynthesize by encouraging healthy foliage.
- Phosphorus (P): Phosphorus helps promote healthy root development, flowering, and fruit.
- Potassium (K): Potassium helps plants regulate water intake, resist drought conditions or other stresses.
Fertilizers can also include other micronutrients, like magnesium, zinc, iron, calcium, and more.
The N-P-K ratio you should be looking for may change based on the type of plant. Typically, a fertilizer label will list a series of numbers. So, if you’re seeing 20-20-20, that means there’s an equal amount of Nitrogen (N), Phosphorus (P), and Potassium (K). Fertilizers will often say what type of plant they benefit most on the label as well, but keep an eye out for balanced rates as these will be the most all-purpose.
Pour It: Liquid Fertilizer
Liquid fertilizer is just what it sounds like—you give it to your plant in liquid form. But it's sold as a concentration, so you’ll have to dilute it.
- Control: You can easily control how much you use, which means cutting down on amount or frequency is all up to you.
- Added to water: You’re already watering your plants. It’s not hard to throw some fertilizer in there as well! No extra steps…well, besides measuring.
- Ugh, measurements: You have to measure it to dilute it properly. A mistake in measuring over and over can compound to cause damage to your plants—so play it safe and dilute even more than the packaging recommends.
Shake It: Granular Fertilizer
Granular fertilizer is typically shaken into the soil and mixed in. The granules have a water-soluble coating, so the nutrients are released as soon as you water the plant.
- Quick: You shake it, you water. It doesn’t get much quicker than that!
- Hard to mix in soil: It’s really only possible to use this one at the top of the plant. You can’t get a very thorough mixing when your soil is already in a pot.
- Super easy to overdo it: Even if you follow the instructions, it’s pretty easy to overdo it. Not to mention, hard to control the distribution.
Spike It: Slow-Release Fertilizer
These are generally seen as fertilizer spikes, although sometimes the granules can be slow-release as well (look for this specifically called out on the packaging). You can place these in your plant’s soil and they slowly release the nutrients over time. There are mixed results with these—some people refer to them as “steroid sticks,” and some refer to them as “murder sticks.”
- Spike and forget it: These spikes make it pretty easy to fertilize your plants. You literally just spike it and forget it.
- Unable to control the release of nutrients: Sure it says slow release, but you have no control over how slow or fast.
- Too close to roots: It can be hard to get the distribution just right and you can risk placing a spike right next to sensitive roots that will easily burn with such close contact.
Natural and organic fertilizer is an excellent option when considering fertilizers. It's also available as liquid concentrations and slow release granules or spikes. However, it's less likely that you'll find precise N-P-K ratios on the all-natural stuff because well, natural also means variable.
And if you want to go a step further, you can even use eggshells or home composting as a perk for your houseplant!
- Provides Microbes: Using natural fertilizers has the added bonus of friendly microbes that promote healthier soil, ultimately making nutrients more available to the plant!
- No salt buildup: Synthetic fertilizers use salts to make the nutrients water-soluble, but with natural fertilizer there is no salt—and so no salt buildup!
- It’s eco-friendly or even waste-free: Friendly to the environment! Renewable! Biodegradable! All excellent things. And if you're going DIY, it’s also waste-free. 😌
- You have no idea how much NPK is in your natural fertilizer: A bit harder to calibrate specific needs for specific plants
- Using too much is still a bad idea: Just like synthetic fertilizer, you can over-do it. But on the bright side, it's much gentler because it naturally takes longer to break down.
A Note on Foliar Feeding
You may see fertilizer sold as a "foliar spray," which means it is intended for spraying directly on a plant's leaves. This is a controversial one.
Some swear by it, but ultimately, the path that mother nature designed for nutrient delivery was through the roots.
It should also be noted that only some plants can successfully absorb a worthwhile amount of nutrients through their leaves. But perhaps most importantly, if you DO see results from foliar feeding, it likely means your plant is quite desperate for nutrients and there's a deficiency you need to address...through the roots!
How (and How Often) to Use Fertilizer
When you decide on a fertilizer, you’ll have instructions directly on the packaging that outline measurements with a quick how-to. But we’ve noticed that these can be a bit fast and loose—so we want to expand on how to use each type of fertilizer. We’ve also noticed the packages typically recommend amounts on the higher side, so we’ve added our two cents on each!
Pour It: Liquid Fertilizer
Liquid fertilizer needs to be diluted at minimum per the package instructions. But we prefer diluting it even more—up to half the recommended amount—to really make sure we aren’t risking our plant’s health. You can prepare the dilution directly in a watering can and then water as you normally would—evenly and thoroughly.
It’s good to use your liquid fertilizer once every couple of waterings in the growing season—you probably don’t want to do it any more than that, so try to keep track! If the soil is very dry, water with plain water first, so your plant doesn’t over-indulge on the fertilizer as they race to quench their thirst. 🥵
Shake It: Granular Fertilizer
Granular fertilizer can be a bit harder to use on houseplants. You’ll typically see two methods:
- Measure the specified amount and sprinkle it over the soil
- Use it while repotting (only really recommended if you're making your own potting mix and are sure it's not already supplemented with nutrients)
Generally, granular fertilizer “activates” upon watering so you'll really want to take a conservative approach when deciding on the quantity. Remember: less is more!
Spike It: Slow-Release Fertilizer
When you use the slow-release spikes, it’s a pretty simple application. The spikes may come with a little tool that allows you to poke a hole in the soil in preparation for the fertilizer stick. If not, you can use something like a (clean) chopstick or skewer to achieve the same thing.
The important thing here is to stay away from the roots.
You don’t want to spike fertilizer right into the stem or root area because it will hurt the plant more than it helps!
The spikes are generally good for multiple months at a time, so you should probably only be doing it once, maybe twice in the growing season. Read the label and add some time on top of what it suggests.
Any commercially available organic fertilizer will work exactly the same way as the above options. In terms of the risk of over-fertilization and damage to roots, it is much safer, so while we still recommend erring on the side of caution, you can be a little less on edge about it all!
You can also try your hand at fertilizing with things you already have at home. This is the only method that doesn’t come with package instructions! We'll cover a few ideas here, but the world is truly your oyster—the options are vast and varied!
- Eggshell powder or tea: Before you use eggshells on your plant, you’ll need to clean them thoroughly with hot water. You can then crush or grind the eggshells into a powder and sprinkle an even layer across the soil. Or after crushing the eggshells, place them in a container to fill with hot water, let steep overnight, then strain out the shells. Use this eggshell tea to water your plant!
- Add a layer of compost: If you’re an at-home composter, you have the perfect natural ingredient to fertilize your plant! You can top off your soil with the compost (just add some to the top) and agitate the soil a bit by poking holes here and there. Give your plant a good watering to distribute.
- Coffee grounds: Humans perk up with coffee, and so do plants! You can do the same thing with used coffee grounds as you would with compost and spread a layer across the top of the soil. Don’t go too crazy with this or you may be asking for a mold issue!
- Banana peels: Banana peels have all three ingredients that a typical fertilizer does: nitrogen, potassium, and phosphorous. You can create a banana peel tea by soaking the peels in water for a couple of days and then using that to water your plants. You can also chop up the peel and place the pieces directly on the soil for a natural "slow release" fertilizer.
A Little Goes a Long Way
It may surprise you that our indoor plants aren’t super needy when it comes to fertilization. Growth is tied directly to the amount of light the plant receives before all other factors. It’s natural to want to pamper our plant babies, but just make sure you don’t kill them with an overabundance of love (in this case: fertilizer). You don’t need to lay off the affirmations or lullabies, though!