Keep your indoor plants thriving

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

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

In nature, plants find these nutrients in the earth’s soil. Once they’ve used all the nutrients in close proximity, they’ll reach farther and farther away by growing their roots. When indoors, a plant’s whole universe is inside a pot. As their human caretaker (and the one responsible for keeping them in said pot) you’ll need to replenish that universe by either replacing the soil (repotting) or fertilizing. The most common way to fertilize is to purchase a prepackaged formula that will provide all the nutrients a plant needs to grow and remain healthy.

A more uncommon, less scientific, way is to toss your orange and grapefruit peels into your plant’s pot. This is a method I use often as I’m not always as diligent as I should be with adding a packaged fertilizer. I wouldn’t necessarily recommend this as the only mode of fertilization but I do have one plant on my kitchen window sill that has grown into a small four-foot-tall bush with only citrus peels. 

Plant fertilizer contains three main nutrients; nitrogen (N) which encourages leaves and stems to grow (the “green” portion of a plant), phosphorus (P) for root expansion and blooms, and potassium (K) for disease fighting. Generally, look for a fertilizer with nutrient levels between 5 and 15 which will serve most pants well. The three numbers listed on a fertilizer package stand for its NPK ratio. Fertilizers also include micronutrients in smaller quantities; things such as calcium which helps strengthen plant cell walls.

Fertilizers come as 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 vessel, every couple of weeks. For dry powders, sprinkle on top of the soil, then add water. Water soluble granules are usually placed either in the soil or on top and dissolve over time with water. Whichever you use, be careful not to over-fertilize. 

Overfertilizing can kill a plant by “burning” the roots. Root burn happens because most fertilizers contain mineral salts that draw water from the soil and the plants, which results in dehydration. Read the directions on the fertilizer packaging for dilution and always err on the side of less rather than more.

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

Organic fertilizers build up in the soil over time, allowing microbial activity to develop – which is usually a good thing. Synthetic fertilizers are stronger with little smell. Here are the best fertilizers, both organic and synthetic versions, for indoor plants.

Dyna-Grow Liquid Grow Plant Food

This uber-concentrated, synthetic, liquid formula has a slightly lower nitrogen level of 7 which helps prevent “stretchy” growth in your plants. Stretchy growth and elongated, leggy 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 a great choice for indoor flowering plants. To use, add ¼ teaspoon to a gallon of water.

Neptune’s Harvest Fish and Seaweed Fertilizer

If you want to go the natural, organic route, this fertilizer from Neptune’s Harvest is an excellent option, albeit a smellier one (it is 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 overfertilization.

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

Fox Farm Happy Frog All Purpose Fertilizer

Fox Farm’s 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 doing that stretching-out thing. Being organic, it is on the smellier end of the spectrum as far as fertilizers go. If you have a lot of indoor plants, you probably don’t want to add this fertilizer to all of them at the same time in order to mitigate the odor.

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

Jack’s Classic All Purpose

This fertilizer from Jack’s Classic has a comparatively 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 also have outdoor plants. It works equally well on shrubs, trees, perennials, as well as your indoor potted plant family.

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

Dr. Earth Organic and Natural All Purpose

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 pellets on top of the soil of indoor plants every month. 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

Compost and compost tea (the liquid that decomposing matter produces) are also excellent things to add to the soil of your indoor plants. 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 package suggests) as well as grape vine trimmings and other dry manure. It does not, however, smell as bad as that might suggest. In fact; it is surprisingly non-stinky. And it works amazingly well. My dad has always told me that cow manure is the best fertilizer and, while it's true he grew up on a dairy farm and might be slightly biased, it’s also true that this stuff from Malibu Compost seems to really make my indoor plants happy. As one Amazon reviewer commented, “Best crap out there!”

Most plants can withstand sporadic care as long as they have sun and water. Fertilizing, though, helps them grow stronger and fuller, even if it is just a regular dose of citrus peels.