The Best Fertilizers for Indoor Plants Tested in 2023

Help your houseplants thrive by feeding them the best fertilizer for indoor plants.

By Savannah Sher and Mark Wolfe | Updated May 3, 2023 4:37 PM

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The Best Fertilizer for Indoor Plants Option

Photo: Debbie Wolfe

Plants get nearly all the sustenance they need from water and sunlight, but since houseplants live in containers, they do not receive the essential nutrients they need to remain strong, healthy, and pest-free. Fertilizers act as a nutritional supplement, providing houseplants with a combination of micronutrients and macronutrients that allow them to thrive.

After researching dozens of the most popular fertilizers for indoor plants, we gathered nine of the top performers. Then we tested them for a month on our own potted plants to learn more about their effectiveness for different plants, soils, and growing environments. Ahead, preview the list of tested products and then follow along as we showcase the best fertilizer for indoor plants.

  1. BEST OVERALL: Espoma Organic Indoor Plant Food
  2. BEST BANG FOR THE BUCK: Miracle-Gro Water Soluble All-Purpose Plant Food
  3. BEST ORGANIC: Neptune’s Harvest Fish-Seaweed Blend Fertilizer
  4. BEST SLOW-RELEASE: Osmocote Outdoor & Indoor Smart-Release Plant Food
  5. BEST LIQUID: Dyna-Gro Grow 7-9-5 Liquid Plant Food
  6. BEST FOR CACTUS: Grow More Cactus Juice Cacti & Succulents Fertilizer
  7. BEST FOR FLOWERING PLANTS: JR Peters Jack’s Classic 10-30-20 Blossom Booster
  8. BEST FOR HERBS: Dr. Earth Organic Life All Purpose Fertilizer
  9. BEST ALL-PURPOSE: JR Peters Jack’s Classic 20-20-20 Plant Food
The Best Fertilizer for Indoor Plants Option

Photo: Debbie Wolfe

How We Tested the Best Fertilizers for Indoor Plants

Our tests encompassed different fertilizer types such as organic and synthetic options as well as liquid concentrates, water-soluble granules, and dry-application formulas. To obtain comparable results, we set up a trial with nine groups of five houseplants each. All of the plants were healthy and growing in 6-inch pots. Seven of the groups were made up of common foliage plants like pothos, dracaena, snake plant, and croton, and two specialty groups featured cacti and succulents in addition to flowering houseplants.

We tested these fertilizers from early February through early March, starting as the plants completed a semi-dormant phase. We repotted the plants into fresh potting soils that had no added plant food. After a week of acclimatization in the new soil, we began the recommended fertilization programs as directed on each fertilizer label.

Throughout testing, we monitored for any changes in plant health and vigor, foliage color, new growth, and infestation by insects or diseases. In addition to these measurements of product effectiveness, we also compared the up-front costs of the products along with the application rates, storage, mixing, and user convenience to get a clearer picture of the overall value. Finally, we recorded our observations, scored each product on a scoring rubric, and then gave the following awards to each product based on performance.

The Best Fertilizer for Indoor Plants Option

Photo: Debbie Wolfe

Our Top Picks

We tested the best indoor plant fertilizers for a range of specific houseplant needs. If you’re looking for the best plant food for your indoor home garden, check out these reviews.

Best Overall

The Best Fertilizer for Indoor Plants Option: Espoma Organic Indoor Plant Food
Photo: amazon.com

Espoma’s organic indoor plant food has a nitrogen-phosphorus-potassium (NPK) ratio of 2-2-2, which means that it features a balanced mixture of macronutrients to benefit a wide variety of houseplants. It’s made with natural ingredients, making it a perfect choice for organic gardening. Since the macronutrient percentages are relatively low, this product is an excellent pick for beginners who tend to overfertilize plants.

To use this Espoma product, mix 2 teaspoons of the liquid fertilizer with 1 quart of water, and then thoroughly saturate the plant’s soil. According to the manufacturer, it should be applied every 2 to 4 weeks.

In our test, the Espoma organic indoor houseplant food proved effective and easy to use. The small size and sturdy bottle made it easy to work with and simple to store. The mild formula did not deliver a fast burst of growth, but after two applications within a month, the plants grew out healthy and attractive, with no noticeable insect or disease issues.

It’s worth noting that the fertilizer’s smell was notably less pungent than other organic fertilizers we’ve tested, and the odor did not persist long after application. As a concentrated liquid plant food, we had to mix the product with water. The instructions conveniently referenced filling the cap “halfway” as a measuring tool, but the cap did not have a reference line to show the exact measurement. So we estimated about 2 teaspoons worth in the cap, and it worked out just fine.

While buyers may be able to take advantage of periodic sale prices, even at the base price we were pleased to note that it was the most affordable organic houseplant fertilizer we tested in terms of both the purchase price and cost per application. The natural plant food ingredients and added beneficial microbes are proven to enhance nutrient absorption and minimize waste when used as directed.

Read our full review: Espoma Organic Indoor Plant Food

Product Specs 

  • Type: Organic liquid concentrate
  • Size: 8 ounces
  • NPK: 2-2-2

Pros

  • Balanced NPK in a concentrated liquid formula that’s easy to mix and apply
  • Organic fertilizer includes humic acid and beneficial microbes to maximize plant health
  • Compact size and sturdy bottle make it easy to handle and store
  • Budget-friendly; one of the most affordable organic fertilizers available

Cons

  • 8-ounce size is less economical for big plant collections; larger sizes are not available
  • Requires frequent applications for best results

Get the Espoma fertilizer for indoor plants at Amazon or Ace Hardware.

Best Bang For The Buck

The Best Fertilizer for Indoor Plants Option: Miracle-Gro Water Soluble All-Purpose Plant Food
Photo: amazon.com

This Miracle-Gro indoor plant food has a unique granular formula designed to be mixed with water for a more even application. During a plant’s active growth period, apply this fertilizer every 1 to 2 weeks.

This formula has an NPK ratio of 24-8-16, which means a high nitrogen content, so it’s an excellent all-around pick for green houseplants but may not be the best choice for flowering plants since it’s low in phosphorus. While this small 8-ounce package should be sufficient to fertilize houseplants over one season, larger sizes are available.

Miracle-Gro has been around for generations, and our test results show the reason why. It was easy to use, easy to store, produced zero smell, delivered fast results, and was the least expensive of all the fertilizers tested on a per-application basis.

Sustainability can be a complicated discussion when it comes to fertilizer, but the makers of this chemical-based plant food made a good effort. The highly concentrated fertilizer granules were vacuum sealed inside a plastic bag packed in a recyclable cardboard box. Minimal packaging paired with a high fertilizer density makes for an efficient system that generates less plastic waste over time than any of the organic fertilizers, packed in plastic bags and jugs, that we tested.

To mix up a batch, we used the included measuring scoop to add the granules to the watering can first, and then added water. The granules instantly dissolved without clumping, and no stirring was necessary. The solution gave off no smell. We swept up the few spilled granules and returned them to the package.

We fed our plants twice with Miracle-Gro—the first time a week after repotting and the second time 2 weeks later. We liked alternating plant food applications with plain water between feedings to prevent buildup of plant food residue in the soil. The plants responded well. They all sent out a flush of fresh new growth that began about 2 days after the first treatment. By the end of the test month, the new growth was beginning to harden off and the plants looked great.

Our only concern with this fertilizer, which we could not test with the time or equipment we had available, was the potential for nutrient runoff. This occurs when unused, water-soluble nutrients flow out of the soil with later watering, which not only wastes nutrients but can subsequently contribute to pollution. Excess nitrogen and phosphorus from private septic systems and municipal sewage treatment facilities can contaminate groundwater and cause unchecked algae growth in streams, lakes, and rivers. Users are advised to capture and reuse houseplant drain water, thereby reducing the risk of nutrient runoff.

This product is highly concentrated, so we used caution to only soak the soil—but not to the point of runoff—when feeding. But any unused plant food would have been flushed out the following week when we heavily applied plain water. Even with careful fertilizing and watering, it’s best to save drain water when using this and other water-soluble fertilizers.

Product Specs 

  • Type: Water-soluble granules
  • Size: 0.5, 3, 5, 5.5, 6.25, and 10 pounds
  • NPK: 24-8-16

Pros

  • General purpose 24-8-16 formula promotes growth and overall plant health
  • One 8-ounce package can fertilize houseplants for a whole season
  • Works for both houseplants and outdoor garden plants
  • Lowest purchase price and the lowest cost per application of all the fertilizers we tested

Cons

  • The low phosphorus ratio is not ideal for flowering plants
  • Highly concentrated formula may contribute to nutrient pollution if not applied correctly

Get the Miracle-Gro fertilizer for indoor plants at Amazon or Ace Hardware.

Best Organic

The Best Fertilizer for Indoor Plants Option: Neptune’s Harvest Fish-Seaweed Blend Fertilizer
Photo: amazon.com

This organic fertilizer from Neptune’s Harvest is formulated with a combination of fresh fish and seaweed from the North Atlantic. It’s certified by OMRI, so users can rest assured that it’s made exclusively with natural and organic ingredients.

For houseplants, the manufacturer recommends mixing a tablespoon of the liquid formula into a gallon of water before thoroughly saturating the plant’s soil. For best results, it should be reapplied every 1 to 2 weeks. With an NPK ratio of 2-3-1, it contains a high percentage of phosphorus, which is ideal for flowering plants. Since its macronutrient content is relatively low, even novice users are unlikely to inadvertently overfertilize their plants.

We loved the results from Neptune’s Harvest fish and seaweed fertilizer, but the smell could be overwhelming. We mixed the concentrate with water according to the label instructions and fed our plants every 2 weeks. The results after our month-long test were excellent: lush new growth and no symptoms of overfertilization or infestation.

One detail we found lacking in this product was a measuring device. Although we discovered that one capful approximates the required tablespoon per gallon of water, measuring with the cap was messy. Unlike the purpose-designed cap of the Espoma product above, this is just a regular cap. It needed to be thoroughly cleaned after measuring, or else the bottle would become a smelly mess.

And the smell is acute, especially in its undiluted state. It is not horrible like rotten fish but just an intense fish smell that lingers for a day or so after feeding. In a poorly ventilated space, it may not be ideal. But the nutrient analysis is just right for stimulating root and bud development, so this could be an excellent choice for cultivating seedlings, reducing transplant shock, and boosting flowering plants.

Product Specs 

  • Type: Liquid
  • Size: 18 ounces, 36 ounces, 1 gallon, and 5 gallons
  • NPK: 2-3-1

Pros

  • A short list of minimally processed natural plant food ingredients
  • OMRI listed for use in organic gardening and farming systems
  • Concentrated liquid formula is easy to mix and easy to apply
  • Generous phosphorus content is ideal for stimulating root and flower production

Cons

  • Strong fish smell lingers around recently fed plants for about a day
  • Does not include a measuring cup or spoon for mixing the solution

Get the Neptune’s Harvest fertilizer for indoor plants at Amazon, Gardener’s Supply Company, or Burpee.

Best Slow-Release

The Best Fertilizer for Indoor Plants Option: Osmocote Outdoor & Indoor Smart-Release Plant Food
Photo: amazon.com

Like most slow-release fertilizers, these granules from Osmocote are coated with a semipermeable resin shell that releases nutrients slowly based on temperature, ensuring that houseplants receive the supplements they need during their active growing periods. The pellets need to be applied every 6 months.

This 2-pound container will last for a long time if users feed only indoor plants. Application rates are based on the size of the container. A houseplant in a 2-gallon container only requires 1.5 tablespoons.

We anticipated some difficulty gauging the effectiveness of a slow-release fertilizer, but we were pleasantly surprised. In addition to being extremely easy to apply, the Osmocote fertilizer also delivered noticeable results within our testing time frame.

We used the included measuring scoop to apply the fertilizer pellets on the soil surface in each pot. To reduce the chance of the loose pellets washing, blowing, or falling out, we gently drilled them into the soil surface with a chopstick. (An easier method would have been to mix the fertilizer with the potting soil at repotting time.) After that, we simply watered as needed, which was about once a week.

The test plants perked up and began adding new growth right on schedule. Within a month they had a nice new flush of foliage maturing. Everything about them looked strong and healthy. The best part was that we didn’t need to mix up fertilizer or follow a weekly or biweekly routine throughout the growing season.

Although the purchase price was slightly higher than some of the other fertilizers we used, Osmocote’s value shines through in the season-long feeding that it provides. It worked out to be one of the least expensive options on a cost-per-application basis (approximately $.32 per application for 2 gallons of soil), and it eliminated the hassle of mixing solutions and keeping up with a feeding schedule. Twice a year would suffice.

Product Specs

  • Type: Slow-release pellets
  • Size: 1, 2, 4.5, and 8 pounds
  • NPK: 15-9-12

Pros

  • Continuously feeds potted plants or garden beds for up to 6 months
  • Available in 4 different sizes for smaller or larger gardens
  • Outstanding value because of the fertilizer value and labor savings

Cons

  • Difficult to measure the right amount accurately for pots less than 1 quart (less than 6-inch diameter)

Get the Osmocote fertilizer for indoor plants at Amazon, Ace Hardware, or Lowe’s.

Best Liquid

The Best Fertilizer for Indoor Plants Option: Dyna-Gro Grow 7-9-5 Liquid Plant Food
Photo: amazon.com

This concentrated liquid fertilizer from Dyna-Gro requires mixing just ¼ to ½ teaspoon of fertilizer per gallon of water. With a 7-9-5 NPK ratio, this formula is high in nitrogen and phosphorus and suitable for fostering growth in flowering plants. It also works well as an all-purpose fertilizer. It’s marketed as suitable for indoor and outdoor plants as well as for lawn care and ornamental flowers.

Measuring the minuscule amount of concentrate needed for a quart of plant food (a quarter of a quarter teaspoon, or .042 ounce) was the most difficult part of working with the Dyna-Gro fertilizer. Because of the tiny amount required, we mixed up a gallon of fertilizer solution and stored the extra three quarts until needed. This supplied enough plant food for the whole month-long product test but required us to store the extra solution. Of course, users with larger plant collections likely would not run into this issue because they would probably use up at least a gallon of plant food at a time.

We liked that this fertilizer contained a well-rounded balance of micronutrients in addition to the NPK content. It provided 2 percent calcium, along with traces of magnesium, boron, chlorine, cobalt, copper, iron, manganese, molybdenum, sodium, and zinc—all of which are required for long-term plant health.

Our results with Dyna-Gro were similar to those using Osmocote, but not as rapid as with Miracle-Gro. The plants produced a healthy flush of new foliage with no symptoms of stress, disease, or insect infestation. This was the only synthetic fertilizer that we applied with each watering, so our long-term concern was that residue could accumulate in the soil and cause problems with extended use. When using this product long term, buyers should monitor their plants for signs of stress and flush the soil with clear water.

We also noted that the manufacturer offers recommendations for different application rates to fit a variety of growing situations. Users may feed at each watering (as we did) with a solution of ¼ or ½ teaspoon per gallon of water, or increase the ratio to 1 teaspoon per gallon for a biweekly or monthly feeding schedule. Instructions are also given for use in hydroponic systems, siphon feeders, irrigation injectors, or for foliar spray.

Product Specs 

  • Type: Water-soluble
  • Size: 8 ounces, 32 ounces, and 1 gallon
  • NPK: 7-9-5

Pros

  • Balanced nutrient formula is perfect for flowering plants and foliage plants
  • Ultraconcentrated liquid is a budget-friendly choice for feeding large plant collections
  • In addition to potted plants, this product can be used in hydroponics and outdoor gardens

Cons

  • The highly concentrated formula is difficult to measure accurately in small amounts

Get the Dyna-Gro fertilizer for indoor plants at Amazon, Saratoga Organics, or Greenhouse Megastore.

Best For Cactus

The Best Fertilizer for Indoor Plants Option: Grow More Cactus Juice Cacti & Succulents Fertilizer
Photo: amazon.com

Cacti and succulents have unique nutritional needs and thus require an NPK ratio different from other houseplants. Featuring a low quantity of nitrogen and higher levels of phosphorus and potassium and a macronutrient balance of 1-7-6, Cactus Juice fertilizer is crafted specifically to cater to those needs. It also includes calcium, an additional benefit for cacti and other drought-resistant plants.

To use, mix 1 teaspoon of plant food with a gallon of water and apply it to the cactus’s soil. Since it’s a liquid formula, reapply it every 1 to 2 weeks during the growing season.

It was much more difficult to gauge our success with Cactus Juice compared to the other fertilizers we tested. The test cacti simply didn’t grow as quickly as other types of houseplants, and we didn’t expect them to. But they looked great and continued to improve throughout the month of testing. The color of the foliage deepened noticeably, and the first hints of flower buds began to appear by the end of the month. In short, everything progressed as it should.

Like most of the other liquid fertilizers we tested, this one did not include a measuring device. Using a measuring spoon to gauge the bottle cap volume, we found that half a capful approximates a teaspoon, so we used it to measure afterward. But then we had to clean it thoroughly before replacing it on the bottle. The tall, narrow 16-ounce bottle itself was easy to handle and poured cleanly.

Product Specs 

  • Type: Liquid
  • Size: 16 ounces
  • NPK: 1-7-6

Pros

  • Specially formulated with low nitrogen for cacti and succulents
  • Value price point; a great choice for feeding large cacti collections
  • Includes NPK plus calcium to support healthy plant tissue and drought resistance

Cons

  • Must be applied frequently for best results
  • Specifically for cacti and succulents; not recommended for use on other plants

Get the Grow More fertilizer for indoor plants at Amazon, The Home Depot, or Do My Own.

Best For Flowering Plants

The Best Fertilizer for Indoor Plants Option: JR Peters Jack’s Classic 10-30-20 Blossom Booster
Photo: amazon.com

Growing flowering plants indoors can be tricky, and one reason that a plant isn’t producing flowers can be that it lacks phosphorus. This Jack’s Classic fertilizer, with a 10-30-20 NPK ratio, is patently designed to increase the number of blooms on flowering plants and ensure that their petals are bright and vibrant. It’s equally proficient at feeding indoor and outdoor plants, including fruits and vegetables.

Add ½ teaspoon of the water-soluble formula to a gallon of water for the ideal mixture. Reapply every 2 weeks for the best results.

We fed Jack’s Classic Blossom Booster to two African violets, two Reiger begonias, and a phalaenopsis orchid. It’s important to note that all of these plants had just completed a resting phase when we started the feeding test. By the end of the month, both the violets and begonias had begun to produce an abundance of new flowers, while the orchid had begun to produce a new flower spike.

The fertilizer arrived sealed inside a plastic bag, packed in a plastic tub, and came with its own measuring scoop. The granules dissolved instantly in water with no clumps and no need to stir.

The 1.5-pound size could be a bit much for those with just one or two plants. However, it is labeled for use on “all indoor and outdoor flowering plants,” so even plant lovers with just a handful of house and patio plants will likely find it broadly useful. At about $.04 per feeding, this specialty plant food was very cost-effective and produced really good results for very different types of flowering plants in our test.

Product Specs 

  • Type: Water-soluble granules
  • Size: 1.5 pounds
  • NPK: 10-30-20

Pros

  • The 10-30-20 NPK content is perfect for flowering plants indoors or outdoors
  • It’s also suitable for boosting vegetable and fruit production in the garden
  • Nourishes plants by feeding through both the roots and the leaves

Cons

  • Highly concentrated, immediate-release fertilizer risks overfertilizing if not used according to the label instructions

Get the JR Peters Blossom Booster fertilizer for indoor plants at Amazon.

Best For Herbs

The Best Fertilizer for Indoor Plants Option: Dr. Earth Organic Life All Purpose Fertilizer
Photo: amazon.com

Growing herbs, vegetables, and fruit year-round indoors is nearly impossible. Luckily, many varieties can thrive inside as long as they receive plenty of supplemental light and the right nutrients. This all-purpose fertilizer from Dr. Earth is perfect for growing edible plants indoors because of its complex formulation of natural plant food ingredients and beneficial microbes. It’s also easy to use because it doesn’t need to be mixed into the plant’s soil. However, for new plantings, mix the granules into the potting if possible.

While many slow-release formulas use traditional synthetic ingredients, this fertilizer is organic yet feeds plants for up to 2 months at a time. However, for indoor potted plants, the manufacturer recommends reapplying the fertilizer monthly.

We noted that this Dr. Earth fertilizer smells mildly like a hayfield, probably due to the high alfalfa meal content. It also contains fish bone meal, fish meal, and kelp meal that (thankfully) did not emit a noticeable fishy smell while packaged or after application. We used it on potted herb plants in our trial.

As with the Osmocote product, we only needed to apply the Dr. Earth plant food at the beginning of the 4-week test period and then watered as necessary. By the end of the month, our plants looked great, with a beautiful new flush of fresh foliage and buds. The fertilizer was easy to apply, although no measuring scoop was included, and because it contains no animal manure, it produced none of the “off” smells often associated with organics.

The two areas where this product lagged the competition were cost and bulk. The 4-pound bag that we used was larger and less convenient for storage than the others listed, and more product (by volume) is needed per feeding. Also, at $.32 per application, it came in as the second most expensive fertilizer we tested. But for shoppers who are most interested in working with nature to improve the soil and growing edible plants with a reduced risk of nutrient runoff, this Dr. Earth product is one of the best houseplant fertilizers available.

Product Specs

  • Type: Slow-release pellets
  • Size: 1, 4, 12, and 40 pounds
  • NPK: 4-6-5

Pros

  • Organic plant food ingredients are minimally processed from natural sources
  • Suitable for use on culinary herbs and other edible plants
  • Dry formula is easy to apply with a measuring spoon or cup
  • Available in assorted sizes ranging from 1 to 40 pounds

Cons

  • Bulkier and more expensive per application than many of the other products we tested

Get the Dr. Earth fertilizer for indoor plants at Amazon, Ace Hardware, or Do It Best.

Best All-Purpose

The Best Fertilizer for Indoor Plants Option: JR Peters Jack’s Classic 20-20-20 Plant Food
Photo: amazon.com

A balanced ratio of nitrogen, phosphorus, and potassium is generally recognized as the most flexible option for plant fertilizers. This one from Jack’s Classic has an NPK ratio of 20-20-20, offering a high concentration of all three macronutrients.

Jack’s Classic all-purpose plant food is particularly useful for green foliage plants. Mix ½ teaspoon of the granules into a gallon of water and apply it every 2 weeks. This versatile formula works as well on houseplants growing in potting soil as it does on shrubs, trees, herbs, and ornamentals planted in the ground.

This water-soluble plant food was very easy to mix and store. It arrived sealed in a plastic bag that was packed with a measuring scoop inside a plastic tub. As with Miracle-Gro and the other JR Peters product we tested, the granules dissolved instantly in water and were easy to sweep up if some fell on the work surface.

Our plants appreciated the quick burst of nutrients with each feeding. After the first application, we noted deep greening of the foliage within 3 days and new bud development within a week. The effect of the second application was less like flipping on a light switch and more like nudging a merry-go-round that is already in motion. Growth continued to progress, culminating in a lush new foliage display by month’s end. The plants grew well but not so aggressively that they appeared out of balance.

We liked the ease of use and low cost of the Jack’s Classic product, but buyers should use caution. Mix and apply strictly according to the label directions to avoid overfertilizing, waste, and excessive nutrient runoff.

Product Specs

  • Type: Water-soluble granules
  • Size: 8 ounces, 1.5 pounds, 4 pounds, and 10 pounds
  • NPK: 20-20-20

Pros

  • The balanced 20-20-20 formula works for most plant types indoors and out
  • Water-soluble granules are easy to measure, mix, apply, and store
  • Affordable price at only $.04 per application in our tests

Cons

  • Careless use may lead to plant damage or nutrient pollution

Get the JR Peters 20-20-20 fertilizer for indoor plants at Amazon.

Jump to Our Top Picks



What to Consider When Choosing a Fertilizer for Indoor Plants

While it’s easy to assume that all indoor plant fertilizers offer similar performance, several factors affect their functionality. Keep reading to learn about several of the most important features to consider when choosing the best houseplant fertilizer.

Types of Fertilizers for Indoor Plants

The three primary types of houseplant fertilizer are liquid, granular, and slow-release pellets. Each kind has advantages and disadvantages.

Liquid

Before applying it to a plant’s leaves or soil, a liquid fertilizer must be mixed with water, which requires some additional measuring. However, the water makes liquid plant foods easier to apply sparingly and avoid overfertilization. Liquid plant foods are typically best for those with many houseplants because a large amount of water must be used to dilute very little fertilizer. However, liquid indoor plant fertilizers move through soil and plant systems rapidly and must be applied frequently—every 1 to 2 weeks.

Granular

Granular fertilizers are affordable and effective. Simply sprinkle the fertilizer on top of the soil, then mix or water it in. Synthetic fertilizer granules gradually dissolve as the plant is watered, typically within about 30 days. Organic plant food nutrients are released by soil microbial activity, also within about a month. Use a granular houseplant fertilizer when initially planting or repotting a plant so it can be thoroughly mixed into the soil. It typically must be reapplied after 4 to 6 weeks.

Slow Release

Slow-release indoor plant fertilizers come in several formats, including pellets, spikes, pods, and capsules. Because they emit nutrients gradually, they can last from 3 to 6 months. They’re typically only available in traditional—not organic—formulas.

NPK Ratio and Plant Species

The best fertilizers contain a mixture of macronutrients—nitrogen (N), phosphorus (P), and potassium (K)—along with traces of micronutrients. The balance of these three macronutrients is represented by its NPK guaranteed analysis, which is listed on the fertilizer’s packaging. For example, a guaranteed analysis of 10-10-10 means that 10 percent of the fertilizer, by weight, is nitrogen; 10 percent is phosphorus; and 10 percent is potassium. The remaining 70 percent can be made up of any combination of micronutrients and inert ingredients. Explicit details are shown on the back of the houseplant fertilizer label.

The guaranteed analysis is sometimes converted to an NPK ratio. For instance, 10-10-10 fertilizer has a ratio of 1-1-1, whereas 10-30-20 fertilizer has an NPK ratio of 1-3-2. The NPK ratio is a good way to compare different brands and formulations of fertilizers. Three different fertilizers may have three different analyses, for example, 5-5-5, 10-10-10, and 20-20-20, but the same 1-1-1 NPK ratio. This comparison could indicate that the products may work for the same plant types, using different application rates.

Because each plant species has different nutritional needs, a “perfect” NPK ratio doesn’t exist. Generally, green houseplants require a balanced NPK ratio or one that’s slightly higher in nitrogen. A higher balance of phosphorus is particularly beneficial for flowering plants such as African violets, oxalis, and peace lilies. Phosphorus also aids in fruit production, making it beneficial to edible plants. Potassium is closely linked to general plant health, healthy cellular structure, and drought resistance.

Organic or Traditional

One of the primary decisions shoppers must make is choosing between a traditional or an organic fertilizer.

  • Organic fertilizers are made entirely from minimally processed natural ingredients. Although organic fertilizers are free of potentially harmful chemicals and synthetics, their nutrient values aren’t as concentrated as traditional products. Moreover, over time, their natural content can emit an unpleasant odor. Since the marketing term “natural” isn’t regulated particularly well in fertilizers, look for a product that’s been approved for certified organic use by the OMRI.
  • Traditional, or synthetic, houseplant fertilizers contain a blend of minerals balanced for feeding houseplants. Typically costing less than organic fertilizers, they come in more concentrated formulas.

Application

A fertilizer’s ease of application depends largely on whether it’s a liquid, granular, or slow-release formula.

  • Liquid fertilizers must be diluted with water according to the manufacturer’s instructions. Pour liquid fertilizers onto the plant’s soil, or if directed by the manufacturer’s instructions, some liquid fertilizers may be absorbed through plant foliage.
  • Granular fertilizers can be sprinkled evenly on the soil’s surface and mixed into the top 3 inches of soil before it’s watered, which releases the nutrients.
  • Slow-release fertilizers vary in application method. Follow the manufacturer’s instructions for fertilizing with pods, spikes, pellets, or capsules.

Tips for Using the Best Fertilizer for Indoor Plants

Following these tips help ensure your plants thrive without risking overfertilization.

  • Since all fertilizers are different, follow the instructions on the manufacturer’s label.
  • Avoid over-fertilization. Reduce your fertilizing schedule if your plant’s leaves droop or begin to look burnt at the edges.
  • Avoid fertilizing plants that are stressed by drought, disease, or insect infestation. Treat the problem first, then fertilize after the plant recovers.
  • Know how to recognize nutritional deficiency based on leaf color: Browning leaves lack potassium; yellow leaves indicate nitrogen deficiency; and purple leaves often mean the plant lacks phosphorus.
  • There’s no need to fertilize most houseplants during their dormant season if you live in an area that experiences standard seasonal temperature changes.

FAQs

While you now know more about choosing the best plant fertilizer for indoor plants, you might still want more information about how to use it. Here are some answers to some of the most frequently asked questions about fertilizing indoor plants.

Q. Why do indoor plants need fertilizer?

Houseplants have been removed from their natural habitat and are therefore lacking the macronutrients and micronutrients present in their native soil that help them remain healthy. Fertilizers supplement these nutrients.

Q. What’s in houseplant fertilizer?

Houseplant fertilizers contain a mixture of macronutrients (nitrogen, phosphorus, and potassium) and micronutrients that supplement the nutrients already in the plant’s soil.

Q. How do I fertilize indoor plants?

The fertilization method depends on the chosen formula. Add powder and granular fertilizers to the plant’s soil, and then water. Dilute liquid fertilizers with water before application.

Q. How often should I fertilize indoor houseplants?

The ideal fertilization schedule depends on the type of fertilizer you choose. Liquid fertilizer should be applied every 2 to 4 weeks, whereas a granular fertilizer only needs to be applied every 4 to 6 weeks. Fertilize with a slow-release formula every 3 to 6 months.

Q. Can you overfertilize houseplants?

Overfertilization is a common problem with houseplants. The signs of overfertilization vary depending on the plant species, but they include symptoms like wilting, burnt leaves, and dried leaf margins.

Q. When should I fertilize indoor plants?

Indoor plants typically don’t need fertilizing during their dormant season, which usually takes place over the winter. Start fertilizing your houseplants in early spring, about 8 weeks before the last expected frost. In areas that don’t experience winter frosts, reduce applications to half strength.

Why Trust Bob Vila 

Bob Vila has been America’s Handyman since 1979. As the host of beloved and groundbreaking TV series including “This Old House” and “Bob Vila’s Home Again,” he popularized and became synonymous with “do-it-yourself” home improvement.

Over the course of his decades-long career, Bob Vila has helped millions of people build, renovate, repair, and live better each day—a tradition that continues today with expert yet accessible home advice. The Bob Vila team distills need-to-know information into project tutorials, maintenance guides, tool 101s, and more. These home and garden experts then thoroughly research, vet, and recommend products that support homeowners, renters, DIYers, and professionals in their to-do lists.

Meet the Tester

Mark Wolfe is a writer and product tester with a background in the nursery and landscaping industry. For more than 20 years, he mowed, edged, planted, pruned, cultivated, irrigated, and renovated beautiful landscapes. Now he tests and writes reviews about the latest outdoor power equipment, hand tools, lawn-care products, and other outdoor-living goods.