Fertilizing House Plants 101

Fertilizing House Plants 101

5 minute read

We receive a lot of questions about house plant fertilizing from the community. “Do I need to fertilize my house plants?”, “What kind of fertilizer should I use?”, “When should I fertilize my plants?” are just some of the frequently asked questions we receive. So today, we are going to explain how, when, and why you should fertilize your house plants!

a person adding coffee grounds to their house plants soils

Firstly, fertilizer is not the same as plant food. Although there are many commercially sold plant food products on the market, they are not really required. Why? Because plants naturally make their own food! How? By the process of photosynthesizing!

Photosynthesis [ˌfōdōˈsinTHəsəs] NOUN

The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water. 

Fertilizers, although they are not naturally produced by plants, deliver nutrients to help your house plants survive in the soil they are planted in. Since house plants are grown indoors and potted in containers, they do not receive a natural supply of organic matter that plants growing outdoors or in the wild receive. Fertilizing your soil will help add the needed nutrients that plants require to thrive.

a photo of a perosn adding slow-release fertilizer to their house plants soil

What kind of fertilizer should I use?

Fertilizers come in many different forms and can be synthetic or organic. Synthetic fertilizers work quickly but can deplete some healthy organisms needed for long-term, healthy soil. Organic fertilizers work slowly and add nutrients to the soil rather than feed the plant directly. Think of them as more like supplements for your soil.

Regardless of what you choose, a good fertilizer needs a balance in macronutrients. You will often find the letters N – P – K on packaged fertilizers with a number value next to them. These letters stand for Nitrogen, Phosphorus, and Potassium and are the 3 main essential nutrients for house plants. The recommended values for these 3 nutrients will vary on the type of house plant you want to fertilizer. We recommend doing some quick research to see which values are best for your plant. Other macronutrients include magnesium, calcium, and sulfur. 

Micronutrients are required in smaller amounts and include boron, molybdenum, chlorine, copper, iron, and manganese.

a photo of liquid fertilizer a photo os blue coloured fertilizer granules

Fertilizers can be liquid or granular form. These are added to water and are great for people who like to control how much and when they fertilize their plants

a photo os slow-release fertilizer pellets a photo of a hand holding slow-release fertilizer capsules to the soil of their Snake Plant

Fertilizers can also come in slow-release spikes, pellets, or capsules. These are great for people who are forgetful or have less time on their hands. Check your plant soil for small round beads as many growers and nurseries tend to add slow-release fertilizer capsules to their soil mix. They can come in a variety of colours but are commonly green or pale yellow.

a photo of a banana peel under soil in a plastic containera photo of a plate full of crushed eggshells and used coffee grounds

Some house plant enthusiasts prefer using natural or homemade fertilizers such as fish emulsion, compost tea, kelp, bone meals, etc. Some easy household fertilizers include bananas (high in potassium), coffee grounds (good for adding nitrogen), eggshells (nitrogen + calcium), Epsom salts (magnesium + sulfur) just to name a few. Household fertilizers are a great way of reducing waste, but you would need to figure out the right ratios on your own to ensure that your plant is getting the right amount of macro and micronutrients.

Tip: Specific fertilizers for certain species of plants can be found in the market. For example, there are fertilizers specifically formulated for cacti, orchids, and even air plants! 

Important note: Always follow the instructions on the product labels! Over-fertilizing your plants can be harmful to them.

a photo of a person mixing fertilizer into fresh house plant soil

When should I fertilize my plants?

Fertilizing is recommended during the growing seasons of spring and summer. Again, remember to follow the instructions on the label! Most house plants go through a dormancy stage in the fall and winter when temperatures drop and there is less daily sunlight. Avoid Fertilizing during this time to give them a rest period. You will also want to avoid fertilizing your plants for 6-8 weeks right after you have repotted them. This will avoid adding any additional stressors while the plant is recovering from being repot.

What happens if I accidentally over-fertilize my house plants?

When introducing anything new to your plants, start slow. If you are still unsure, it is always better to under-fertilize than over-fertilize your plants. Signs that you’ve over-fertilized your house plants include:

- Quickly wilting leaves

- Fertilizer burns – yellow blotching and brown leaf tips

- Sudden leaf drop

- Stunted growth

- Fertilizer crust on the surface of the soil (white in colour and looks like salt)

If you suspect that you have over-fertilized your plant, you can leach out some fertilizer with a long watering. This will help to flush out excess fertilizers. If there is fertilizer crust on top of the soil then it needs to be removed first before leaching the soil, as this process can break down the build-up and drag it down towards the root system.

At the end of the day, less is more when it comes to using fertilizers and they should always be used with caution and attention. A yearly or bi-yearly repotting of soil should also decrease your need to fertilize your house plants as often. Happy growing!


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