How To Fertilize Indoor and Outdoor Plants (Ultimate Guide)

Everyone wants to grow and maintain healthy and happy plants. Whether your plants live in your home or outside in your backyard, knowing how to fertilize and care for them can make a difference for everyone involved. 

You can fertilize your indoor and outdoor plants by providing fertilization and water on a seasonal schedule. It is best to use a fertilizer with the ingredients that your specific plants need and provide them with the right amount of fertilization. 

Continue reading to learn more about fertilizing your indoor and outdoor plants in this ultimate guide. I will also talk about the many differences between indoor and outdoor plants.

What Is Fertilizer and Why Should I Use It?

Everyone knows that you should water and feed your plants on a regular schedule to keep them healthy and alive, right? Well, not necessarily. Not every plant owner is familiar with the concept of fertilizer.

Fertilizer is a natural mixture of chemicals and additives that supply nutrients to your plant to help it grow. Plant owners should utilize fertilizer regularly to help maintain their plant’s health as it blossoms throughout the year. 

Fertilizer is most common in the agricultural world and is a more “in-depth” plant feeding treatment. Plant owners are not as aware of fertilizer as gardeners and agricultural experts are. 

Although many feed their plants with fertilizer here and there, not many know that fertilizer is a frequent form of food for plants

Every fertilizer, especially in commercial agriculture, contains a hefty amount of three main ingredients:

  • Nitrogen: Helps plants remain nutritious and abundant for eating once fully grown. 
  • Phosphorus: Used to help plants blossom and flower. 
  • Potassium: Helps strengthen your plant’s roots.

Individuals may also find other ingredients in their fertilizers as well. This will, ultimately, depend on the fertilizer that is used: 

  • Iron: Helps with the flow of oxygen in the plant. 
  • Zinc: Helps with the metabolic reaction in plants for overall growth.
  • Boron: Contributes to the movement, structure, and building of sugar in plants.
  • Sulfur: Helps the plant grow smoothly and correctly. 
  • Calcium: Helps the plant build an internal network.
  • Magnesium: Activates certain enzymes in plants. 

Like people, plants love added nutrients in their diet because they can grow big and strong. Water and sunlight are lovely additions to a plant’s overall health, but fertilizer helps maintain a healthy soil composition full of nutrients.

Indoor and outdoor plants can both use fertilizer as food for growth. Fertilizer might not always be necessary, but it is becoming more popular worldwide. 

If you add fertilizer to your plant feeding regime, the following might happen: 

  • Your plant will grow larger than average with fertilizer. 
  • Your plant’s performance will increase, and it will grow to be strong. 
  • If your plant produces any food or flowering, it will be abundant. 
  • The root system of your plant will become structured and firm. 
  • Protein and enzymes will enhance, and they will be able to survive easier. 
  • If possible, fruit and nut production can occur. 

How Often Do You Fertilize Your Plants?

Fertilizer is an excellent addition to the plant world. It can produce significant health and wellness for all of your plant friends. However, it is vital that fertilizer is used cautiously because, if overused, it can cause issues. 

You should fertilize your plants on a specific schedule that aligns with your plant’s growing season. This can be specific to the seasons and can be adjusted, depending on the plant that you have.  

Every plant is different and unique to its kind, but all plants require nutrition of some form. Water and sunlight are great options, as previously mentioned. However, some plants can strengthen quickly with the use of fertilization. 

Fertilizers should be applied through the following seasons: 

  • The spring season: Fertilization should be applied two months before the last frost is experienced, and fertilization should not be as strong. 
  • The summer season: Fertilization should be at its normal rate but may differ on the type of fertilizer you use for your plants. 
  • The fall season begins: To pull back on how much fertilizer is used two months before the first expected frost. 
  • The winter season: Most plants should not be fertilized in the winter. Some outdoor plants might not apply to this general rule, but all houseplants should be left alone. 

Most fertilizers should be applied every three weeks and up. The time frame in between fertilization may depend on the season, plant, and environment. 

If you are seeking advice on a particular plant that you would like to fertilize, it is best to begin researching that plant. There are thousands of plants in the world, and some plants have specific nutrition needs for their overall health.  

It may also be essential to note that some plants, especially ones that flower or produce food, can last longer in between fertilizations. 

Fertilizing Indoor Plants 

Indoor plants have become a trend. As more people become plant moms and dads, they are beginning to research how to take care of their new plant friends. Unfortunately, it can be challenging to take care of every indoor plant in one regime. 

Fertilization can help indoor plants thrive in their environment. The fertilization of an indoor plant should follow a strict regime, and fertilization should not be over-applied. If a plant receives too much fertilization, it can become hazardous for the plant. 

Indoor house plants should not be touched with fertilization during the winter season. Plants are inactive and not in a growth phase, so fertilization won’t help during the winter months. 


The first cycle of fertilization should begin in the spring, which is when plants exit their dormant phase and become more active. The weather is supportive during this time of year, and plants are preparing to blossom. 

Here are some recommended tips for fertilizing your plants in the spring: 

  • Less is always more. Too much, as previously mentioned, becomes hazardous for your plant. This is especially true in the springtime. 
  • Apply fertilizer with less strength or half the amount for the first three cycles. Your plants are coming out of their winter phase, and do not need a full dose. 
  • Your plants will not tell you when they need fertilizer like they would need water. 
  • Begin by choosing a natural fertilizer that you feel comfortable with. 


The second cycle of fertilization is in the summer. Plants will be fully active during this season, and can handle more fertilization. Your plant’s fertilization schedule and dosage should be specific to the fertilizer you use.

Some fertilizers require only a few weeks in between each application while others can go up to four months.  

Here are some recommended tips for fertilizing your plants in the summer: 

  • Choose a fertilizer you feel comfortable with. 
  • Apply the correct amount – nothing more or less. 
  • Pick a fertilizer that meshes with your schedule, and follow it correctly. 
  • Keep to the schedule even if your plants come outside during part of the summer. 

If you want to learn more about fertilizing houseplants in the summer, you can check out my other article: How Often Should You Fertilize Houseplants in the Summer?


The last season you will apply fertilization for your indoor plants is in the fall. During this season, you will want to reduce the amount of fertilizer you use, and prepare your plants for entering a dormant period. 

Here are some great tips for fall fertilization: 

  • Take it slow and begin to taper off similarly to how you would in the spring. 
  • Measure or pay attention to the weather, so you know when to begin. 
  • Watch and monitor the health of your plants. 

Fertilizing Outdoor Plants 

It can seem silly to think that outdoor and indoor plants are different, but they are. They grow and adapt to their environments differently, and they have many needs that are specific to their kind. 

When fertilizing outdoor plants, it can be valuable to decide if the plants you are feeding are rooted in the ground or planted in a pot. Even if the two plants you wish to fertilize are similar, they will be treated differently with fertilization and their schedules may differ. 

All outdoor plants should be fertilized in the beginning of spring just as indoor plants are. All plants are in a more active phase of growth during the summer time, and nutrients will help them remain healthy and happy. 

If you live in a city that is higher in elevation, it is best to wait the cold months out before applying fertilization in the springtime. If you apply fertilization and frost forms overnight, the process may get tainted. 

For all outdoor plants rooted in the ground, fertilization should be applied at the peak of their growing season. It is recommended to use a slow-release fertilizer for outdoor plants. 

Slow-release fertilizer will release fertilizer at a slow rate over a few months. This helps with your plant’s health, especially if plants will flower or produce fruits, vegetables, and nuts. 

Potted plants can have liquid fertilization once a month during their active seasons. 

Outdoor plants do not need fertilization in the winter months, similarly to indoor plants, and will be tapered off with fertilization during the fall. 

How Do I Know What Kind of Fertilizer To Use?

It’s no secret that there are many different types of fertilizers out there in the world. Although all of them are helpful, it is best for plant owners to find a fertilizer that matches their overall intentions as well as their plant’s needs. 

You will know what type of fertilizer to use because it matches the needs of the plant you are feeding. Every plant is different, and certain fertilizers work better than others. All fertilizers also have dosage amounts on their packaging for easy access. 

Every fertilizer will have the proportions of the main three ingredients that most, if not all, fertilizers contain:

  • Phosphorus
  • Nitrogen
  • Potassium

Each fertilizer will contain a specific amount of those nutrients in their package. It is always best to choose a fertilizer that has the right portion size for the specific plant you are looking for. This can be determined by soil testing. 

If you are seeking a fertilizer for a particular houseplant and you aren’t interested in doing soil testing, you can ask for advice from a professional. Some plants follow a generic guideline, and professionals can recommend a specific brand or option. 

Additionally, there are homemade plant fertilizers and fertilizers that are homeopathic. Individuals can also add certain organic additions to their plants, like coffee grounds and epsom salt. 

Types of Fertilizers

There are a few different types of fertilizers that you can use for your indoor and outdoor plants. Most times, the fertilizer you use depends on your personal preference. 

All types of fertilizers will come in organic and non-organic compounds. Regardless of what type of fertilizer you use, all plants will need the three main ingredients: nitrogen, phosphorus, and potassium. 

Fertilizer can be administered in a few different ways: 

  • Slow and controlled release fertilizers
  • Dry fertilizers
  • Liquid fertilizers

Organic and Non-Organic Fertilizers

Fertilizer provides plants with nutrients. However, the nutrients can come from living or nonliving materials. Regardless of which type of fertilizer you choose, plants will react to their fertilizer in one way or another, and begin to grow. 

Organic fertilizer comes from natural plant and animal ingredients while inorganic fertilizer comes from non-living material. 

The most common organic fertilizer is manure, which is used during the planting process. This is very common for vegetable plants. However, fertilizer has to also be added after the planting process.

The only issue with organic fertilizer is that it does not provide quick access to ingredients. If desired, individuals can add a little bit of inorganic fertilizer with the organic fertilizer for quick access. 

Inorganic fertilizer, rather than organic, has few ingredients, which is why it is so popular. It gives plants a direct source to what they need: 

  • Nitrogen
  • Potassium 
  • Phosphorus 
  • Sulfur 
  • Nitrate

Slow and Controlled Release Fertilizers

This type of fertilizer is self-explanatory and relatively popular in the gardening world. If you have a large garden or are looking for a great fertilizer for outdoor plants, this one might be for you. 

Slow and controlled release fertilizers target the root and are applied at the beginning of the spring usually. They slowly release fertilizer over time, and may not need to be touched for up to four months. 

This fertilizer helps with feeding the root and providing immediate nutrients for rapid growth at a slower rate, and all of the fertilizer will get used up. 

Dry Fertilizer

Dry fertilizer is a great option for plant owners as well, especially when first beginning the fertilization process. This type of fertilization comes in a dry pellet formula and can be applied more than one way. 

Depending on what type of plants or garden you have, you can measure out the fertilizer and sprinkle it around your plant. If you are adding it to a garden, it is best to make sure it is all evenly dispersed. 

Fertilizer should be added before planting as well as afterwards for the best results. 

Liquid Fertilizer 

This type of fertilizer is super popular for gardens that specifically focus on growing vegetables. Vegetables, as well as many other plants, do well with a quick nutrient boost and that is just what liquid fertilizer does. 

This type of fertilizer is usually applied once a week every week. Most liquid fertilizer options are a crystallized formula or liquid that is mixed with water. It is the best type of fertilization if your plants need immediate nutrition. 

It can be poured onto the leaves of your plant or into the soil. 

Determining the Ingredient Ratio for My Fertilizer

There are so many fertilizers out there to choose from, and all of them have different directions for application. It can be challenging to discover the right fertilizer that has the best quantity for your plant. 

Luckily, there are some easy ways to discover how you can determine how much fertilizer to use for your plants. If you feel uncomfortable with measuring out the right amount for yourself, it is always best to use less. 

If you notice that you barely fed your plant any fertilizer, you can always add more later. As mentioned prior, fertilizer can kill your plants if you add too much of it. 

The first step to determining how much fertilizer you should use is to determine what type of plant you are fertilizing. Here are some factors to take into account: 

  • Figure out what type of plant you have, how large it is, and how many you have. 
  • Measure the square footage of your garden, if applicable. 
  • Decide if your fertilizer will be for indoor or outdoor plants. 
  • Determine if your plant will be contained and potted or rooted in the ground. 

The amount of fertilizer you use will differ, depending on your plants. Outdoor plants tend to work well with dry and/or slow and controlled release fertilizer. Indoor plants, on the other hand, do well with liquid fertilizer and use much less. 

Fertilizers will, ultimately, be measured out by weight. It is recommended to test your soil’s condition before choosing your formula. This can be especially valuable for large gardens and outdoor plants that are rooted in the ground. 

All fertilizers have specific ingredients, and it is best to choose a fertilizer that contains the right amount of additives for your plants. 

Some fertilizers contain more of nitrogen and less of potassium, while others – it is the opposite. 

How Do I Read the Ingredients on the Fertilizer Packaging?

If you’re a beginner with gardening and fertilization, reading the numbers on a fertilization package can feel like you’re trying to interpret another language. The right knowledge and skill can actually make it an easy process. 

You can read the ingredients on the fertilizer packaging by interpreting the three numbers with dashes on them as the quantities (in pounds) of nitrogen, phosphorus, and potassium per package. The number may look something like so: 10 – 5 – 10. 

Once you determine the proper ratio of ingredients for your plant(s), reading the packaging becomes much easier. As mentioned prior, having professional help with determining the right ratio for your plant is helpful. If you are testing your soil, this is especially recommended. 

Each number in the sequence on the packaging represents how much, in pounds, there is of an ingredient. If the packaging says “10-5-10,” it is normal to expect that ten pounds of nitrogen, five pounds of phosphorus, and ten pounds of potassium exist in the overall 20-pound bag. 

Sometimes, other additives are listed as ingredients on the packaging, but that is not as necessary. What is most important is that your plants are receiving these three main ingredients. 

Applying the Fertilizer 

Fertilization is an easy process, once you get the hang of it. It can seem like a frightening task at first, but it becomes a job well-done when you and your plants enter a routine that works wonderfully. 

Once you determine what ratio you need, what plants you are fertilizing, and what type of fertilizer you will use, you will be ready to apply your fertilizer. Indoor plants and outdoor plants can be applied similarly but are very diverse in the fertilization process. 

For outdoor plants or gardens, fertilization should be measured in weight. Two pounds (0.9 kg) is a great starting point for one-hundred square feet (9.29 square meters). You can add an extra pound (0.45 kg) if necessary, but going beyond that may harm your plants. This measurement amount would be sufficient for a garden that is ten feet by ten feet (3.04 x 3.04 meters). 

Outdoor plants can have a similar process to indoor plants, if they are potted or a singular plant that you are fertilizing. Indoor plants tend to mesh well with water-based fertilizer, and they do not need very much of it. 

For water-based fertilizers, a half of a teaspoon (4.92 ml) should be mixed into one gallon (3.78 liters) of water. If you are measuring the soil, one tablespoon (14.78 ml) should cover one gallon (3.78 liters) of soil. This measurement can be applicable for indoor potted plants and even some outdoor plants. 

Is There a Difference in Fertilization for Indoor and Outdoor Plants?

All plants are unique in their own way and vastly different. However, just like people, all plants have relatively similar needs. Indoor and outdoor plants can both benefit from fertilization, even though there are slight differences. 

There is a difference in fertilization for indoor and outdoor plants because indoor and outdoor plants react differently to fertilization, have different soil, and are in different environments. All in all, certain types of fertilization work well for certain plants. 

Indoor plants are in a sheltered environment, even though they may be outside in the summer season. Due to this, they react differently to the food and hydration they receive. Their entire environment helps them cope with survival in a specific way. 

Outdoor plants, on the other hand, are usually planted in the ground and receive plenty of sunlight and fresh air throughout the year. This can differ based on location, but outdoor plants are still in an outdoor environment. 

In choosing fertilization, it is best to conduct research on the plant(s) that you are fertilizing. Some experts recommend specific types of fertilizer over others for certain plants. 

When fertilizing an outdoor plant, here are a few things to take into consideration: 

  • Outdoor plants are exposed to many environmental factors, including sunlight. 
  • Outdoor plants do well with a slow-and-controlled release application. 
  • Many outdoor plants flower and produce seeds, vegetables, or fruit. 
  • The environment outdoors is completely different, especially if your plant is rooted. 
  • Although organic fertilizer is great, many outdoor plants need quick access to nutrients. 
  • Fertilization should be watched over and carefully dispersed throughout the season.
  • Gardens are different from singular plants or potted plants. 

When fertilizing an indoor plant, here are a few things to take into consideration: 

  • Indoor plants are sheltered in a temperature-controlled environment. 
  • Indoor plants are potted and shaded most of the time, with some sunlight in the summer.
  • If your plant is potted or indoors, it should be watered before fertilized. 
  • Indoor plants can benefit from fertilization but should be given a small amount since it is only one plant. 
  • Liquid-based formulas do great for indoor plants. 

Some Plants Should Not Be Fertilized 

The winter season is off-limits for fertilization because plants, indoor and outdoors, don’t grow. Some plants, in fact, don’t ever need fertilization, even in the spring, summer, and fall. This is because of their genetic make-up.

Get to know your plant before and after planting it. Fertilization should not be added or used unless you know it will benefit your plant. Even though there are many fantastic plant foods out there in the garden world, they are not always great for your specific species of plants. 

There are natural additives that can be added into the soil of your garden or pot to enhance the nutrients that your plant eats. This is suggested for plants that don’t need fertilization or for plant owners who might not be comfortable with using fertilization at all. 

There are many plants that do not blossom from fertilization. Some of the most common ones include: 

  • Perennials of all kinds 
  • Trees
  • Shrubs

Fertilizer should also be limited on plants that have sensitive roots or plants that have yellow undergrowth. Some indoor plants can get by without fertilization as well because of their environment. 

This option will depend on the preference of the plant owner.  

Alternatives to Fertilizer

If you are new to the fertilizing world, it’s normal to feel frightful about the process of feeding your plant. Although fertilizer is the talk of the town, it also can cause you a lot of work and, if not applied properly, can harm your plants. 

There are alternative options for individuals that might not feel safe using fertilizer or are not ready to take that step yet. 

The first step individuals should take is to incorporate additives into their soil to provide nutrients and hydration. 

Here are some great options: 

  • Remove any rocks, weeds, or dirt that could impact the overall growth process.
  • Provide fresh soil for your plants before planting them. 
  • Add a good amount of compost to your soil for positive growth. 

Manure is a popular compost option. Others include:

  • Epsom salt 
  • Coffee grounds
  • Vegetable scraps and grass clippings 
  • Wood chips, leaves, and hay 

It is also best that your soil is moisturized and full of nutrients. Some plants work well with certain types of compost while others don’t.

Can I Use an Indoor Fertilizer on an Outdoor Plant?

Finding the right plant food for your plants is important. However, many fertilizers contain the same ingredients and can be used for a few different plants that you have. 

You can use an indoor fertilizer on an outdoor plant if the fertilizer contains ingredients that may benefit both plants. Some indoor fertilizers cannot be dualistic while others can. It is essential for individuals to read the labels and to double check before fertilizing. 

There are many different fertilizers on the market. Some of them are specific for outdoor plants while others are for indoor plants. Every fertilizer has a different ingredient ratio, and some might not work well with your plants if they aren’t the right match.

Luckily, there are some great fertilizers out there that can work as both an indoor and outdoor fertilizer. Most plants need the same nutrients but different amounts and application processes. 

It is recommended to match any plant food up with your plants to make sure that they are a great fit for what you need.

What To Look For in Fertilizers

Once you are educated and knowledgeable about what your plant needs, finding fertilization and applying it can be easy. Your plant and its soil will tell you what they need for plant food, water, and other additives if necessary. 

When looking at fertilizers, there are a few necessary things to keep in mind about your plant(s): 

  • Whether you are looking for a fertilizer for an indoor or outdoor plant, or both
  • Whether it’s a potted plant or a plant that has roots in the ground
  • Whether your plant has sunlight or shade
  • The weather conditions and seasons your plant may experience
  • How large your plant is, and what it needs
  • The ingredients on the label, and the ingredients needed for your plant
  • Your soil’s test results or the condition of your soil

While shopping, there are recommended ingredients that can be added into your plants. A soil test can give you information on what ingredients will work well with your plants, and you can then choose a fertilizer based on that information.

However, there are ingredients that can be helpful for plants and soil in the right dosage, even if you don’t do a soil test: 

  • Nitrogen, potassium, and phosphorus are the most important ingredients. 
  • Additional additives like calcium, oxygen, hydrogen, magnesium, and sulfur are useful.
  • Extra minerals like nickel, iron, zinc, copper, cobalt, and chlorine can increase plant growth.

Will Synthetic Fertilizers Hurt My Plants?

Food can either hurt us or help us thrive, and the same idea is true for our plants. Fertilizer acts as a plant food, and can be very helpful. But, it can also have the opposite effect if used inappropriately. 

Synthetic fertilizers can hurt your plants if used poorly or too often. Synthetic fertilizers contain toxins and chemicals that can be hazardous to your soil and to the environment. This type of fertilization creates toxicity in the groundwater over time. 

Synthetic fertilizers are wonderful for many plants and have become a popular necessity for plant owners and gardeners everywhere. 

They provide quick nutrient boosts and help plants thrive. However, there are some side effects that come along with this type of fertilization. The soil may become tainted over time from the chemicals in this fertilizer. 

Due to this, the toxins can impact the environment, the groundwater, and can even influence those around us that interact with our plants. This is especially true for our animals and children. 

There is a solution to this issue for those of us that choose to use a synthetic fertilizer: 

  • Dilute your fertilizer with water so that the chemicals aren’t as strong. 
  • Mix the fertilizer into the soil well so that it absorbs and won’t leak into the groundwater. 
  • Wash all fruit and vegetables produced with synthetic fertilizer before eating them. 
  • Consider mixing the fertilizer with organic material. 
  • Permanently switch to organic fertilizers.

What Happens if I Over-Fertilize My Plants?

Synthetic and organic fertilizers both have their benefits and disadvantages. It appears as if fertilizer is a helpful option for our plants, but it can still be a frightful thought to think that applying fertilizer wrongly could harm our plants.

If you over-fertilize your plants, they may begin to die, and the soil will become tainted. If you over-fertilize a little bit once or twice, you might not have a huge issue at hand. However, the growth of your plant may stop. 

Fertilizer is specifically helpful for plants outdoors that are in large bunches, and it is common to add a lot of fertilizer to gardens and even landscapes. In this process, the amount of fertilization is extremely important. 

Fertilizer is often overused unknowingly, and the wrong types of fertilizer can cause extreme damage to your soil. If you are growing fruit and vegetables, the fertilizer will impact your plant’s production and the outcome of your harvest. 

While fertilizing your plants, check for these warning signs to make sure your fertilizer is not harming your plants: 

  • There will be a crust-like surface on your soil, and it won’t feel or look nourishing. 
  • The leaves closest to the soil will begin to yellow and appear as if they are dying.
  • Your plant will stop growing or it will grow at a much slower rate than expected. 
  • The tips of your leaves will turn brown. 
  • The roots will weaken, and they’ll look like they are rotting. 
  • There’s little to zero production and flowering, if desired. 

Whether you use an organic or synthetic option, the amount of fertilization matters. Watch over your plants, keep them hydrated with water and sunlight, and use your expert knowledge to fertilize them sparingly. 

If you wonder how to fix over-fertilized soil, you could check out my other article: How To Fix Over-Fertilized Soil (Complete Guide)


Plants are wonderful, and watching them grow is a fun experience. Fortunately, fertilization can help our plants in miraculous ways with the right care. 

If you are interested in fertilization, educate yourself with knowledge and skill. Choose your fertilizer, apply it correctly, and watch your beautiful plants blossom through every season. 

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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