Fertilizing Indoor Plants: All You Need To Know

Fertilizing indoor plants is important. I can’t say it often enough: Don’t forget to feed your houseplants during the growing season! You’ve probably heard somewhere that it’s important to feed your plants, but why is that? Maybe you give your plants food now and then, but you don’t know much about the background and the effect of plant food or you are hesitating to give your plants food. 

That is why in this blog I will tell you all about plant nutrition, how it works, how often you should give it and what happens to your plants if you don’t give it nutrition.

Fertilizers contribute to the well-being of your lovely little plants because they provide the plant with all the nutrients it needs to thrive. The right amount of fertilizer with the right frequency can help prevent disease, promote the growth of lush green foliage, encourage flowering, and strengthen the roots and stems of your indoor plants.

Essential Nutrients for Plants

Through photosynthesis, These three elements are obtained from the atmosphere

  1. Hydrogen from water
  2. Carbon from CO2 in the air
  3. Oxygen from water and air

These nutrients obtained from the soil

  1. Nitrogen
  2. Phosphorus
  3. Potassium
  4. Nitrogen
  5. Phosphorus
  6. Potassium
  7. Sulfur
  8. Magnesium
  9. Calcium
  10. Iron
  11. Boron
  12. Manganese
  13. Zinc
  14. Molybdenum
  15. Copper

Six Primary Nutrients: First six nutrients Hydrogen, Carbon, Oxygen, Nitrogen, Phosphorus and Potassium are primary nutrients that your plants require in fairly large quantities. 

Three additional nutrients Calcium, Magnesium and Sulfur also need in much smaller amounts. 

Rest are the micronutrients that plants need in tiny amounts. Healthy soil that is high in organic materials usually contains adequate amounts of each of these micronutrients

Why is it important to fertilize plants?

Fertilizers replenish your soil with the nutrients that the plants are removing from the soil. In most cases, plants are pulling nutrients out of the soil. Fertilizer is used to replace those nutrients and to make sure that there’s enough there to produce flowers or new growth or fruit whatever that may be.

If we think of the outdoor environment you have so many different types of things that are happening outdoors you have soil that’s being made, leaves dropping to the ground, beautiful earthworms underneath the soil, helpful bacteria and helpful fungus. That’s all happening in the environment outside. 

But your potted plants cannot get this opportunity, it’s limited to the potting soil. That’s why you actually have to recreate in your home to the greatest extent and that’s why we have fertilizers to help. 

Fertilizer numbers meaning (NPK ratio)

Organic or mineral, the vast majority of the fertilizers you use to fertilize your indoor plants consist of the three basic nutrients, called NPK. This three-letter acronym stands for Nitrogen, Phosphorus and Potassium according to their respective chemical symbols.

  • “N” is the chemical symbol for nitrogen. It facilitates photosynthesis, develops foliage and stimulates the growth of green plants.
  • P” is phosphorus. Strengthens the roots and promotes flowering.
  • “K” stands for Potassium or “Kalium” in Latin. Strengthens stems and helps fight disease.

Types of Fertilizer for Indoor Plants

Besides homemade compost, there are two main types of commercially available houseplant fertilizer: organic fertilizer (or natural fertilizer) or mineral fertilizer (or chemical fertilizer).

Organic vs Synthetic Fertilizers

What is Organic Fertilizer: Natural or organic fertilizers essentially mean that they are coming from organic sources like from the earth or living things. They can be either animal-derived or plant-derived. Some examples would be worm castings, mushroom manure, bone meal,  blood meal, cottonseed meal, kelp meal, cow, poultry or horse manure (aged) and compost.

What is Synthetic Fertilizer: A synthetic or non-organic fertilizer is synthesized in a lab. So if you’re synthesizing something in a lab you could concentrate it more and get a higher number.

So things that you see like 20-20-20 or 17-8-22 are most likely synthetic fertilizers because those are relatively high numbers. Organic fertilizers generally have smaller ratios of those numbers like 2-3-1 and they are extracted from organic sources so it’s much gentler.

Organic vs synthetic fertilizer: what is better? 

Organic vs synthetic fertilizer what is better? Your plants don’t really recognize whether you’re giving them a synthetic or organic fertilizer. However, if you’re trying to build up all those helpful microbes in your container then you might want to stick to organic fertilizers because synthetic fertilizers really don’t help build that up for those organisms.

Building healthy soil isn’t limited to just adding nutrients for your plants, it’s about creating an environment in the soil where microbes like bacteria and fungal activity can flourish. Adding organic fertilizer to the soil will introduce all those beneficial things and help for long-term soil health.

How do you recognize if a plant has too little nutrition?

A nutritional deficiency can manifest itself in various ways. One of the first signs is that your plant is no longer growing well, even though it is growing season. So if you have a plant that doesn’t grow all year round, even during the spring and summer, it may well be that there are too few nutrients in the soil. But your plant can also discolor, then the leaves turn yellow or brown. 

Sometimes new growth looks distorted due to a lack of nutrients, or the new growth remains very small. Too little nutrition can also cause your plant to have too little energy to flower. In more extreme cases, your plant may drop its leaves. 

If you are sure that you give enough water and the plant also gets the right light, but you still drop leaves, then too little nutrition is usually the cause. Your plant can become less resistant due to a lack of nutrients and is therefore more susceptible to infections and bugs. 

In short: your plant can become a bit pathetic. Fortunately, a plant can often recover from this, and the plant food acts as an extra shot of vitamins that will make your plant feel like it again.

When to fertilize indoor plants

You should be fertilizing your plants during the growing season because when your plant is not growing it’s not going to need those extra multivitamins and this varies from place to place. I live in the Northeast and my growing season is spring, summer and fall because in the winter months most of my plants actually go dormant. 

But if you’re somebody who lives in the subtropical and tropical zones of the world then your growing season will be all year-round.

How to Fertilize Indoor Plants

Find the right fertilizer

Before buying fertilizer to feed your indoor green army, you should know that you require a fertilizer that is adapted to the particular needs of the species of plants you have. There are universal fertilizers for indoor plants, others for succulents and cacti.

Water first

Don’t apply the fertilizer to dry soil. Water first, wait some time and apply the fertilizer. The water will help dissolve the nutrients and carry them to the roots. 

Liquid Fertilizer

Very quickly absorbed by the plant, liquid fertilizers quickly and efficiently nourish your indoor plants. They are water-soluble, so you can use them in addition to your daily watering by mixing them with room temperature water. 

When I apply fertilizer to my indoor plants, it’s important to note that I dilute everything by half of the recommended limits. So, if it’s suggested that you apply half a teaspoon per gallon of water, I dilute it to one-fourth teaspoon. It’s best to be conservative when applying fertilizer because applying too much fertilizer too frequently can burn your plants and reduce the ability of plant roots to uptake nutrients.

Granular fertilizers

Fertilizer granules have a porous structure which allows them to diffuse nutrients more slowly in the soil and to make them gradually absorbed by the plant. The minerals remain available in the soil for 2-3 months! This type of fertilizer effectively compensates for nutrient deficiencies in the closed environment of your potted plant, while boosting its growth sustainably. 

To add this fertilizer to your indoor plants, simply bury a small amount of granules around the periphery of the roots in your potted plants once at the start of the season and then give it its daily dose of water. They slowly break down from water, heat, sunlight and/or soil microbes. They last longer and since they are gradual in action, it is easier to use the controlled dose. 

Read the Instructions Carefully

It seems like an obvious thing, but many plants have died of overfeeding as people do not read the packaging and do not pay attention to the measures and methods of application. Read carefully and follow the instructions exactly, especially regarding quantity and frequency. 

Avoid overdoing It

An excess of nutrients will not make your plant look prettier, grow faster or have more flowers. Too much fertilizer can burn roots, stunt growth, and even kill your plant. So do not go to the top, in this case, it is better to miss a little than that. 

Fertilizing Different Types of Indoor Plants

The roots of garden plants can spread throughout the soil for nutrients, but indoor plants grown in pots are completely dependent on you for the minerals they need, which is why fertilizing in the right time and right amount is very important.

Houseplants generally need an equal balance of all three minerals, such as 10-10-10 but some varieties may vary, such as those listed below.

Cactus & Succulents

Although cacti and succulents are relatively low maintenance and can survive without feeding, a specialized cactus fertilizer (low in nitrogen) will promote growth and flowering.

Foliage Plants

Most house plant fertilizers are high in nitrogen to make leafy plants look lush and green. Choose a fertilizer rich in nitrogen that also contains magnesium to give the yellow leaves a stimulating effect. Reduce feeding to once a month in the fall and stop completely during the winter months.

Flowering Plants

Flowering plants should be given a houseplant fertilizer every two weeks in the spring. In the period before flowering, you can increase this frequency to a weekly feed, with a fertilizer rich in potassium. Dilute your fertilizer by half the recommended dose, as it may be too potent for houseplants.

Will your plant die if you don’t give plant food?

You may be wondering how important plant food really is, it may be that you never give plant food and your plants still do just fine. That’s a bonus! Your plant will also not die so quickly if you do not give plant food. However, you have a much earlier chance that leaves will turn yellow and fall off and that your plant will no longer grow as well. 

The susceptibility to pests is also greater. With plant food you are therefore assured of a beautiful and healthy plant whose leaves develop well and you see new growth appear.

Can you overfeed your plant?

You can certainly overfeed your plants and that can be harmful. An overdose of plant food can damage the roots of your plant. Therefore, never give more than is stated on the package, and certainly do not give an extra dose if you have forgotten it once. A normal dose of nutrition gives the best result.

Best Practices for Fertilizing Indoor Plants

Fertilize only healthy plants. If you notice any signs of distress, such as yellowing leaves or a fading green color, do not give it high-dose fertilizer. The plant is then unable to absorb the minerals! Instead, try to act differently and wait for active growth to resume before fertilizing it.

Do not fertilize after repotting because the potting soil already has nutrients in its compositions. Instead, wait for 2 to 4 weeks before adding fertilizer to them.

On the same principle, if you buy your plants from a horticulturist, they usually do not need fertilization for 6 weeks.

Always apply the fertilizer on wet soil to your plant and always follow the recommended dosages, so as not to burn the roots of your plants with too high a concentration of fertilizer.

When not to Fertilize Your Indoor Plant 

Don’t fertilize your plant at the end of its growing season. You should not be fertilizing your plant in the dormancy season. So if you’re somebody who lives in the Northeast, the winter is usually the dormant month for most of your plants. They are not growing as quickly as you would want them to grow.

But if you’re somebody who lives in the subtropical and tropical zones of the world then your growing season will be all year-round.

Additionally, I do have to say that some succulents actually go dormant in the summer. So they’re really hot and dry months. So I actually find that some of my plants lose their leaves in the summer months and they start growing them again in the fall and winter months. So then your fertilizing regime would actually be reversed.

So if you want to give your plants the most optimal care, don’t forget to give them some nutrition too! Plant food ensures that your plant is resilient, develops new growth and simply looks much better. Especially in the growing season, from March, give your plants extra nutrition and never give more than the packaging recommends. This way you are assured of beautiful, healthy plants that will be happy in your home for years to come!

I always recommend you to follow our plant care guide to know more about your plant growing season.

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