Soil and water

6 of the Best Houseplant Fertilizers

As most people know, plants get their food from photosynthesis, which is the process of using sunlight to turn water and carbon dioxide into food. But, just like humans, they also need micro and macronutrients to thrive.

These nutrients create enzymes, regulate water and strengthen their defenses against pests and diseases.

How to Fertilize Houseplants

In nature, plants find these nutrients in the earth’s soil. Once they have used up all the nearby nutrients, they will go further and further by growing their roots. Inside, the whole universe of a plant is in a pot. As a human caretaker (and responsible for keeping them in said pot), you will have to replenish this universe by replacing the soil (repotting) or fertilizing. The most common way to fertilize is to buy a prepackaged formula that will provide all the nutrients a plant needs to grow and stay healthy.

A rarer and less scientific way is to throw your orange and grapefruit peels into your plant’s pot. This is a method I use often because I’m not always as diligent as I should be with adding packaged fertilizer. I wouldn’t necessarily recommend this as the only method of fertilizing, but I have a plant on my kitchen windowsill that has grown into a small four foot tall bush with only citrus peel.

Plant food contains three main nutrients; nitrogen (N) which promotes the growth of leaves and stems (the “green” part of a plant), phosphorus (P) for root expansion and flowering, and potassium (K) to control against diseases. As a general rule, look for a fertilizer with nutrient levels between 5 and 15 that will work well for most pants. The three numbers listed on a fertilizer package represent its NPK ratio. Fertilizers also contain micronutrients in smaller amounts; things like calcium which helps strengthen plant cell walls.

Fertilizers come in the form of liquids, water-soluble granules or dry powders – all of which require dilution in water or soil. Use liquid fertilizers, which are mixed with water in a mister or other container, every two weeks. For dry powders, sprinkle on the ground, then add water. Water soluble pellets are usually placed either in the ground or on top and dissolve over time with water. Whatever you use, be careful not to over-fertilize.

Over-fertilizing can kill a plant by “burning” the roots. Root burn occurs because most fertilizers contain mineral salts that draw water from the soil and plants, causing dehydration. Read the instructions on the fertilizer package for dilution and always go for less rather than more.

There are organic and synthetic fertilizers available. Organic fertilizers are made from a natural source of decomposition. This means that they are generally inherently less potent and smellier, as well as more expensive. Although the USDA does not certify organic fertilizers, the non-profit organization Organic Materials Review Institute does.

The best fertilizers for indoor plants

Organic fertilizers build up in the soil over time, allowing microbial activity to thrive, which is usually a good thing. Synthetic fertilizers are stronger with little odor. Here are the best fertilizers, in organic and synthetic versions, for houseplants.

Dyna-Grow Liquid Plant Food

This ultra-concentrated synthetic liquid formula has a nitrogen level of just under 7, which helps prevent “stretchy” growth in your plants. The stretchy growth and elongated, tall plants attract aphids and other insects – not the kind of guests you want to invite into your home. Liquid Grow is also high in phosphorus, making it an excellent choice for indoor flowering plants. To use, add ¼ teaspoon to a gallon of water.

Neptune’s Harvest Fish & Seaweed Fertilizer

Neptune's Harvest Organic Hydrolyzed Fish & Algae Fertilizer 36 0z

If you want to go the natural, organic route, this fertilizer from Neptune’s Harvest is a great option, although it’s smellier (it’s made from dead fish after all). The low NPK ratio of 2-3-1 means you probably don’t have to worry too much about over-fertilizing.

Mix one tablespoon with one gallon of water, then slowly add to your plant’s soil until it is completely saturated. Reapply every two weeks. Neptune’s Harvest is also a small business brand if you strive to shop small and local as often as possible.

Fox Farm Happy Frog All Purpose Fertilizer

FoxFarm Happy Frog All Purpose Fertilizer

Fox Farm All Purpose Organic Powder Fertilizer has a nutrient balance of 6-4-5. The lower proportion of nitrogen means it works well if your plants are stretching. Being organic, it is on the smellier end of the spectrum when it comes to fertilizers. If you have a lot of houseplants, you probably don’t want to add this fertilizer to all of them at once to lessen the smell.

To use, sprinkle a teaspoon on the soil, then add water.

All Purpose Classic Jack’s

Jack's Classic All Purpose Water Soluble Plant Food 20-20-20

Jack’s Classic


This fertilizer from Jack’s Classic has a relatively high NPK ratio of 20-20-20, so be sure not to add too much to your soil. It’s a great choice for an all-purpose fertilizer if you have outdoor plants as well. It works equally well on shrubs, trees, perennials and your family of potted houseplants.

To use, mix ½ teaspoon of granules in a gallon of water. Apply every two weeks.

Dr. Earth Organic and Natural All Purpose

Dr. Earth 736P Life All Purpose Organic Fertilizer in Poly Bag

Dr. Earth’s Fertilizer, a slow-release formula made with organic ingredients, is especially effective on all your indoor edible plants like herbs. It has a balanced NPK ratio of 5-5-5. To use, apply the granules to the soil of houseplants monthly. You don’t have to mix them into the soil like many other similar fertilizers, making it one of the easiest to use.

Malibu Compost Bu’s Blend Biodynamic Compost

Malibu Compost 100507245 Bu's Blend Biodynamic Compost, 12 Quart, 12 Quart, Brown/A

Compost Malibu


Compost and compost tea (the liquid produced by decaying matter) are also great things to add to your houseplant soil. The organic matter in compost enriches your soil holistically. Bu’s Blend is indeed made from cow manure (as the picture of the cow on the packaging suggests) as well as vine trimmings and other dried manures. However, it doesn’t smell as bad as it might suggest. In reality; it is surprisingly not stinky. And it works incredibly well. My dad always told me that cow manure is the best fertilizer and while it’s true that he grew up on a dairy farm and can be slightly biased, it’s also true that this product from Malibu Compost really seems to make my houseplants happy. As one Amazon reviewer commented, “The best shit out there!”

Most plants can handle sporadic tending as long as they have sun and water. Fertilizing, however, helps them grow stronger and fuller, even if it’s just a regular dose of citrus peel.