7 Best Calathea Fertilizers | How and When to Use

If you want your Calathes to bloom and really bring a tropical feel to your home, you’ll have to use fertilizer to improve the soil. However, there are so many products on the market that it can be seemingly impossible to choose.

Instead of you personally testing different fertilizers, take a look at my top picks for Calathea fertilizers, chosen after loads of research!

What Fertilizer Is Best for Calatheas?

If you don’t have the time to read through the entire list, my top picks for Calathea fertilizers are Neptune’s Harvest Fish & Seaweed Fertilizer, Epsoma’s Organic Indoor Houseplant food, and Jobe’s Indoor Houseplant Fertilizer Spikes.

Neptune's Harvest Fish & Seaweed Fertilizer 2-3-1    

Best Organic Fertilizer for Calathea

Neptune’s Harvest Fish & Seaweed Fertilizer 2-3-1    

An organic, liquid concentrate fertilizer, ideal for instantly boosting and providing nutrients to Calathea.

Espoma Organic Indoor Houseplant Food 2-2-2

Best Liquid Plant Food

Espoma Organic Indoor Houseplant Food 2-2-2

100% organic and a perfect NPK blend for Calathea. A fast-acting liquid concentrate feed that needs adding to water before feeding. 

Jobe’s Indoor Houseplant Fertilizer Spikes 13-4-5

Best Fertilizer Spikes

Jobe’s Indoor Houseplant Fertilizer Spikes 13-4-5

Convenient, mess-free fertilizing for Calathea and a whole range of other houseplants. 

Read on to learn more about each fertilizer’s specifications and application.

Calathea Fertilizer Requirements

Before choosing your fertilizer, keep in mind the following requirements it needs to fulfill. Some fertilizers you’ll find online are aimed at specific plants and are often harmful to other varieties, so make sure to read all about the product before buying it. 

Many of these fertilizers also have micronutrients that are beneficial to Calatheas such as boron, chlorine, copper, and iron). These can promote growth and plant health.

Calathea Fertilizer N-P-K Ratio

For beginners, N-P-K refers to the ratio of nitrogen, phosphorus, and potassium (the K stands for potassium). The best ratio for Calatheas is ideally a balanced fertilizer (or thereabouts). An example of balanced fertilizer is a 10-10-10, while 20-20-20 fertilizers may also work well too (if diluted).

The point is – Calatheas need fertilizers with a more or less even balance of N-P-K. Keep in mind that a 20-20-20 is the same ratio as 1-1-1, but it contains 20% of nitrogen, phosphorus, and potassium each.

Calathea Soil pH and Requirements

It’s best to plant your Calatheas in a potting soil mix with good drainage. They need to retain some moisture, but most of the water should be drained.

When it comes to pH, it should be kept around 6.5 – slightly acidic, but almost completely neutral soil pH.

Granular Vs Liquid Fertilizer

The most obvious difference between these two fertilizers is clear – liquid fertilizers are easier to apply and blend, and they’re also always used the same way.

Granular fertilizers, on the other hand, are cheaper if you buy them in bulk, and they’re easier to overwinter. Liquid fertilizers can start to ‘settle’ if they’re not used for some time, while this is unlikely with granular fertilizers.

It’s also important to point out that granular fertilizers are slow-release fertilizers, whereas liquid fertilizers are fast-acting and need to reapply more regularly.

Lastly, liquid fertilizers have a lower salt content than granular fertilizers. Sodium is generally unnecessary for plants, and a great concentration of sodium will only dry the plant out. A general rule of thumb is – the less salt, the better.

Liquid Concentrates & Sprays

Liquid concentrates often have to be diluted in water to be applied to plants (although it is possible to buy ready-to-use formulas. Different fertilizers have different methods and ratios of concentrate-to-water, so make sure you follow the instructions on the label when melding your concentrate.

Some gardeners prefer liquid fertilizers because they’re much easier to apply compared to dry fertilizers, while they’re no less effective. Plants soak up these fast-acting fertilizers quickly, while dry fertilizers stay in the soil for a longer period and take plants longer to absorb.

When it comes to effectiveness, there’s no difference between the two other than if you want quick results say for an ailing plant, for example, you may choose a liquid and for longer-term results, choose granules.

Slow-Release Fertilizer Granules

Since granules release their contents slowly, they’re better for long-term effects, and it’s possible for them to last for weeks or months. This, however, may not be that important with Calathes, as they don’t need too much fertilization.

However, since they’re slow acting, they’re not a good choice if your Calathea needs an instant dose of fertilizer.

Granules are usually applied with rotary or drop spreaders, but since your Calathes are most likely potted, you can just apply the granules by hand.

Fertilizer Spikes

These are a great solution if you’re prone to forgetting when you last fertilized or don’t want the hassle of regular fertilizing. They typically work out to be more expensive than both liquid and granular fertilizers, however.

Spikes are small to medium-sized ‘blocks’ or spikes of granules (they are already melded, so you have to buy spikes in the appropriate ratio). The ‘spikes’ break down and release nutrients directly into the soil over time. 

They’re the first choice of many gardeners because you basically don’t have to do anything – just stick them in the ground, near the roots.

A word of caution when using fertilizer spikes, watch out for overfertilization and single-spot fertilization. There is a tendency for spikes to only fertilize the immediate area in which they are planted. 

Synthetic Vs Organic Fertilizers for Calathea

Keep in mind that many, so-called ‘synthetic’ fertilizers are actually organic, but people label them as synthetic because they’ve gone through a manufacturing process.

The biggest difference is the release of nutrients, as synthetic fertilizers release nutrients more quickly. When you apply them, they’re already prepared for intake, while nutrients in organic fertilizers need to be broken down (usually by bacteria) before plants take them.

Organic fertilizers also have lower concentrations of nutrients, which makes them deliver a lower dose of nutrients. However, keep in mind that they improve water movement and feed beneficial microbes, according to research from Oregon State University. In addition, they are typically safer for the environment, and nearby water sources and are less harmful to pets.

In a nutshell – synthetic fertilizers are stronger, quicker, and easier to apply, but if you apply too much, you could damage your plants. Organic fertilizers are weaker and release more slowly, but they’re healthier for the plant and it’s difficult to apply too much of them and damage your plant.

7 Best Calathea Fertilizer Reviewed

In the following section, I’ll be listing my personal choices for the best Calathea fertilizers that are currently available to buy at your local store and online.

Pros: 

  • Fast-acting liquid feed
  • Versatile and affordable
  • Gentle N-P-K that won’t cause root or foliage burn

Cons: 

  • More applications may be required compared to other formulas

When it comes to 100% organic and liquid fertilizers, this is a personal favorite and one that will last for more than one season since you can cover about 1000 square feet of soil with one 18-ounce bottle. Plus, you can also use it for all your other plants, not only your Calathes.

Okay, so this isn’t an even blend of N-P-K that Calathea is most partial to, but the ratios in this fast-acting and mild formula are not too far off either and certainly won’t harm your precious indoor plants. 

For me, the biggest advantage of using fish and seaweed fertilizer for Calathea (and other houseplants) is the minimum animal content. 

Aside from fish bone meal (which is found in almost all fertilizers), these fertilizers use seaweeds to get all the necessary nutrients, while most fertilizers get their nutrients from the air, natural gases, phosphate rock, and potash rock.

The shelf life of this fertilizer is also impressive, as you can keep it stored indefinitely before mixing it with water according to the manufacturer. 

How to use: Diluting one tablespoon of fertilizer with a gallon of water is the recommended application rate for houseplants, and applying it once a month will keep your Calathes healthy.

Pros: 

  • A balanced and mild formula so unlikely to burn
  • The fast-acting liquid formula gets to work quickly
  • Also suitable as croton fertilizer, as well as many other popular houseplants 

Cons

  • Some users find the smell off-putting

This liquid fertilizer is ideal for houseplants, and it only needs to be applied once a month – which is not bad when it comes to fast-acting liquid feeds. 

It is super easy to measure and mix, but it comes in a smaller container than the previous entry, so you might need to buy more than one bottle.

While not rich in micronutrients like the seaweed nutrient-rich fertilizer above, this fertilizer has 125 000 000 colony-forming units of bacteria per single milliliter of the solution. 

Some reviewers were put off by the ‘organic-smelling’ nature of this feed but, at the end of the day, it does contain organic ingredients – enough said!

How to use: Combine in a ratio of ½ a bottlecap to a quarter of a gallon, mix well and then drench the soil entirely while watering your Calathea.

Pros:

  • Mess-free and convenient 
  • No unpleasant odor
  • Slow-releasing

Cons:

  • More expensive than other fertilizing methods

These long-lasting spikes provide nutrients for your plants for about two months, meaning they only need to be changed every 60 days. And with 50 spikes in the pack, you should be settled with fertilizer for more than a year.

I used these on my Calathea Dottie. It’s been in the same pot for some time and is due to be re-potted just before the start of the next growing season. As you can imagine, the soil is slowly becoming depleted of nutrients and so the enhanced nitrogen levels in this product have given my beloved plant a new lease of life and will certainly tide it over until I re-pot in new soil.

Since spikes are slow-releasing fertilizers, it is unlikely you will overfertilize your plants, and the amount of work you’ll have on your hands is minimal! All you have to do is remember to insert new spikes every other month.

Although spikes can be expensive, they provide you with an even release of nutrients and ensure that your plants are always well fed. Also, half of the pack is free – something to keep in mind when buying.

How to use: Insert one spike per plant until buried beneath the soil. Repeat after 60 days for the duration of the growing season.

Pros

  • Even balance of nutrients – ideal for calathea
  • Ready-to-use formula
  • Pump action bottle for easy application

Cons

  • Requires frequent feeding

This liquid fertilizer is even easier to apply than other liquid fertilizers because it is ready-to-use and you can directly pump it on top of the soil. 

The only negative is the price, as this liquid fertilizer is a bit pricey for its size – as a container has only 10.2 ounces, which you’ll burn through quickly if you apply it on a weekly basis.

How to use: One or two pumps (two pumps are recommended for pots larger than 6 inches) are enough for a single plant, and the manufacturer recommends weekly application.

Pros

  • Made with organic, vegan ingredients
  • High potassium content is great for potted snake plants

Cons

  • May burn plant roots if placed too close

EarthPod fertilizer comes in the form of pods (a form of spike), with each container filled with 100 capsules. This is a great option for a long-term supply, as a single box has enough fertilizer for five years (if you use it on a single plant).

These spikes release nutrients quicker than my favorite entry, though, and you’ll need to replace them every three weeks. However, taking into account that you can settle your fertilizer needs for the next few years (and at what price!), these spikes are a great option.

The Earthpods brand is trusted when it comes to 100% natural ingredients so there is no risk to your pets and even the packaging itself is 100% recyclable and vegan.

How to use: Just like other spikes, all you need to do is stick it in and water it, and let the spikes do the rest of the work. Just be careful not to insert the pods too close to the roots as some reviewers have raised concerns about fertilizer burn.

Pros

  • Slow-release that can last an entire season
  • Manufacturers guarantee that it won’t burn roots
  • Comes with a handy measuring scoop

Cons

  • High N-P-K ratio that should be diluted for calathea

A granular fertilizer, this product needs to be applied directly into the soil, which requires a bit more work than all the other fertilizers. However, it’s a very slow-release formula, and you only have to apply it once a year.

If you mix the granules into the soil around your Calathea in March at the start of the growing season, you don’t have to add new granules until March, next year. 

I have this in my potting shed because it’s suitable for both indoor and outdoor plant use so it’s a good one to have on standby if you have a wide variety of plants that need feeding. I recommend halving the quantities for use as a Calathea fertilizer.

How to use: Sprinkle ½ scoopful of granules in the soil around your Calathea. Mix well to combine with soil, and water in well. Use one scoop if used for outdoor plants. 

Pros

  • Feeds continuously for 2 months
  • Pre-measured spikes are incredibly easy to use

Cons

  • High risk of root fertilizer burn

My final choice is Miracle-Gro’s indoor spikes. An alternative brand to Jobes and with different nutrients but still a convenient and mess-free way to fertilize your Calathea and all other houseplant fertilizing needs. 

These are higher in phosphorus compared to other fertilizers on my list and I’ve included them simply because of how this will encourage root growth and support the effectiveness of how effective your plant absorbs nitrogen. Important for improving the foliage color of your plants.

An added bonus with these Miracle-Gro spikes is they come with an aerator for making holes. 

How To Use: Press each fertilizer spike into the soil until it is fully covered. Spikes should be placed at least halfway between the snake plant and the container edge.

Follow the included dosage directions to determine how many spikes to use per plant.

How to Apply Fertilizer to Calathea

Once you’ve chosen your fertilizer and you know it’s time to use it (scroll down to the following section to see when exactly should Calatheas be fertilized), it’s time to blend it and apply your fertilizer.

What’s important to remember is to first find out how much fertilizer each one of your plants needs, and only then start making your fertilizer – not the other way around.

Some fertilizer mixes will say, for example, to mix three tablespoons with a liter of water, shake, and spread the mixture evenly among ten plants. However, if you only have five Calatheas, then you only need 1.5 tablespoons and half a liter of water.

How to Apply Liquid Fertilizer

As we now know, liquid fertilizer is easier to apply than granular fertilizer. Follow the instructions on the packaging (different fertilizers need different amounts of water) and pour it into the soil around the plant.

This is a two-step process:

Step 1: adjust the amount of fertilizer according to your needs and prepare the fertilizer blend according to the instructions on the label

Step 2: Apply the fertilizer

Some liquid fertilizers can be applied to foliage, but they’re usually not as effective as fertilizers that are applied directly onto the soil.

Overfertilizing can kill your plants, so make sure not to make too much fertilizer mix – depending on the size of the fertilizer bottle and the ratio of fertilizer to the water, you could only need a cup or a tablespoon of fertilizer for your plants.

How to Apply Granular Fertilizer

Granular fertilizer is a bit more complicated and takes more work.

Step 1 – Find Out How Much Fertilizer You Need

Gauging the amount of fertilizer you need is done the same way as with liquid fertilizer. However, you’ll be using actual granules instead of liquid.

Step 2 – Spread Granules by Hand

If you’re working in a small area, the best way to spread the granules is by hand. Only spread as much as the instructions say (if they say 5 grams per plant, then spread only 5 grams of pre-weighed granules).

Step 3 – Cover and Water the Granules

Cover the granules with soil, as they’ll be vulnerable if they’re left on the surface, and water them immediately after.

That’s it! Your granules will slowly release nutrients into the soil.

How to Apply Fertilizer Spikes

The easiest method of application – take off the cover (sometimes the bottom of the spike has a cover to prevent granules from falling out) and stick it into the soil, following the instructions on the label.

It’s easier to stick the spikes in when the soil is moist, usually after watering the plants.

How to Avoid Calathea Fertilizer Burn

Fertilizer burn is usually caused by fertilizer sticking around in the soil for too long, even after the roots drank up everything they could. That’s why your soil needs to be well-drained. All the excess nutrients will leave with the water.

It also helps if you water your Calathea with distilled water as it will clear any salts that remained in the soil.

When to Fertilize

You should never overfertilize your plants, as that can cause illness. You should also know when to fertilize, not only how to fertilize. Most plants don’t need much fertilization and applying fertilizer a few times a year should be enough. Calatheas are no different.

Calatheas need fertilization from early spring to late summer, which is the growing season for Calathes.

How Often to Fertilize

You should fertilize no more than three times during the season – once in March, July, and September. Young, growing plants, need more fertilization than established plants.

This doesn’t mean that you should overfertilize, though. There’s not exactly an equation you can solve to know exactly how much fertilizer your plants need and how often should you apply it – it’s all based on your personal assessment.

As a rule, try to remember that you shouldn’t fertilize them more than once a month during the growing season, and you should never fertilize them from October to March – the plant is dormant during this period and fertilizer can only hurt them.

Verdict: Best Fertilizers for Calathea

Neptune’s Harvest Fish & Seaweed Fertilizer 2-3-1 is my top pick for Calatheas – it’s 100% natural, widely accessible at its price and you can store it for years if you don’t use it all up in one season. 

Neptune's Harvest Fish & Seaweed Fertilizer 2-3-1    

Best Organic Fertilizer for Calathea

Neptune’s Harvest Fish & Seaweed Fertilizer 2-3-1    

An organic, liquid concentrate fertilizer, ideal for instantly boosting and providing nutrients to Calathea.

I’ve given second place to Espoma’s Organic Indoor Houseplant Food because it offers an even balance of nutrients which is good news for Calathea and it’s a liquid feed that gets to work straight away. 

Espoma Organic Indoor Houseplant Food 2-2-2

Best Liquid Plant Food

Espoma Organic Indoor Houseplant Food 2-2-2

100% organic and a perfect NPK blend for Calathea. A fast-acting liquid concentrate feed that needs adding to water before feeding. 

I selected Jobe’s Fertilizer Spikes as they can last you for a very long time and they’re super easy to apply. Plus, you only have to change the spikes every 60 days and they come in a big pack.

Jobe’s Indoor Houseplant Fertilizer Spikes 13-4-5

Best Fertilizer Spikes

Jobe’s Indoor Houseplant Fertilizer Spikes 13-4-5

Convenient, mess-free fertilizing for Calathea and a whole range of other houseplants. 

FAQ’s Fertilizing Calathea