Fertilizer 101 – How to Fertilize Your Houseplants

Friday May 12, 2023
Fertilizer 101, how to fertilize your plants, fertilization, houseplants, houseplants care, living house, living house plants

Fertilizer 101 – How to properly Fertilize your plants.

We all know that plants need light and water to survive, but fertilizing is also an important aspect of plant care. Fertilizing plants and houseplants during their growing season will provide them with the essential nutrients that they need to continue growing. These essential nutrients include nitrogen (N), phosphorus (P), and potassium (K).

The quality and breakdown of soil are very important to a plant’s growth and overall health. This is why Fertilizer is important to boost the plant’s soil with the nutrients it needs to grow and maintain itself. Proper fertilization is essential to growing healthy, beautiful indoor and outdoor plants.

In an outdoor garden, nature provides rainwater and plants can send their roots searching for food; however, the nutrients available to a houseplant are strictly limited to what nutrients are in the potting soil of its pot.

When a plant is first placed in its soil, it has all the nutrients it needs due to the fertilizer and other additives included in potting soils. After a few months, however, the plant has used up the nutrients and fertilizing is necessary for its health and growth.

PRO-TIP: Always follow the instructions on the label of the fertilizer you are using. It is important to note that, too much chemical-based fertilizer can scorch its leaves or even kill your plant. There are environmental concerns when fertilizers are overused as chemical-based fertilizers can find their way into groundwater supplies.

Using too much fertilizer is often worse than not using enough, over-fertilizing is one of the most common mistakes.

What is fertilizer?

A common misconception is that Fertilizer is a plant’s “food” – This is not the case as plants make their food using sunlight through a process called photosynthesis. Fertilizer acts as a multivitamin that encourages healthy new growth.

Fertilizers' core nutrients, (macronutrients), are nitrogen (N), phosphorus (P), and potassium (K). But can also contain other nutrients and trace minerals that can also help boost the health of your soil.

When a plant’s potting mix loses its nutrient content over time, The only way to replenish these nutrients is to supplement your plant with fertilizer or re-pot your plant with brand new fresh soil which would have fresh nutrients.

Liquid-based Fertilizers

Make sure to do your research and find out the specific nutritional requirements for the plants you are caring for. Liquid fertilizer is a great option because you can easily adjust the amount you give depending on the plants' needs; you can suspend feeding when the plant is dormant or increase it when the plant is growing.

Slow-Release Fertilizers

The downside of using slow-release fertilizers is that they require periodic application. These fertilizers are composed of individual pellets with different coatings that dissolve over a period of time, delivering the nutrients to the soil in a staggered manner. A single application can last between 4 - 9 months.

Granular Fertilizers

Although more commonly used in outdoor gardens, Granular fertilizer can be used for indoor potted houseplants or in garden beds. Granular fertilizer releases its nutrients all at once when the pot is watered, this can make it harder to control how much nutrients your plants receive all at once. This type of fertilizer is quite inexpensive but may not be the most ideal choice for fertilizing houseplants.

Organic VS In-organic fertilizers

When choosing a fertilizer, you generally have two options when it comes to type: Organic or Inorganic (Also referred to as Synthetic).

Inorganic fertilizers are often more potent and contain specific amounts of macro and micronutrients, making them a more economical option when purchased in liquid form. Organic fertilizers, on the other hand, are usually derived from natural sources such as food waste, so they are generally less concentrated.

Organic Fertilizers usually have a more mild concentration and can be ideal for use as an indoor houseplant fertilizer. Organic fertilizer can sometimes be a little more costly than other types, but due to being organic, its safe chemical-free alternative is one that you can feel confident using around pets.

All Purpose vs Specific Fertilizers

All-purpose Fertilizers are a great choice that can be used for a wide range of applications.

Specific Fertilizers can be beneficial if you want a particular combination of nitrogen, phosphorus, and potassium for certain plants or outdoor gardens.

When should I fertilize my plants?

Just like too much light or too much water, too much fertilizer can also have the potential to damage your plants. It is recommended to fertilize houseplants sparingly during their growing season: from early spring to later summer is ideal as this is usually a plants growing period.

Plants thrive when they receive nutrients at a regular interval, which can be every two weeks or once a month depending on the fertilizer. During the growing season, this is the optimal time to apply fertilizer for best results.

Make sure to read the label provided and follow the instructions on the bottle - the recommendations on dilution and frequency can vary by brand and product. 

Note: Plants that have been recently potted or repotted plants will generally not benefit from fertilizer. If this plant was re-potted using fresh potting mix – then it is already packed with nutrients. After replanting your plants, it is recommended to wait two to three months before giving them fertilizer to prevent any possible harm.

If you have recently repotted during the colder months, you should wait until the start of the next growing season to fertilize. What does the information on the fertilizer packaging signify?

There are around 18 essential plant nutrients, 3 of which are prominently displayed on the front of most fertilizer labels. The numbers you observe on a fertilizer label represent the three primary macronutrients that are necessary for the growth of a plant - nitrogen, phosphorus, and potassium. An example of an N-P-K ratio might be 10-10-5.

These numbers will vary and will influence fertilizer choice based on a plant’s specific macronutrient requirements. It is important to remember that when comparing different fertilizers, a higher ratio does not always indicate a better product. Higher ratios mean the fertilizer is more concentrated, so it will need to be mixed with more water before use.

Micronutrients and Trace Minerals

Your fertilizer may also include micronutrients or Trace Minerals.

These can include but are not limited to:

Ammonium – very efficient source of nitrogen which is immediately available to plants

Boron - boron plays a key role in a diverse range of plant functions including cell wall formation and stability, maintenance of structural and functional integrity of biological membranes, movement of sugar or energy into growing parts of plants, and pollination and seed set

Calcium - calcium leads to greater root mass and faster, better growth in spring. It also helps promote plant uniformity

Copper - copper activates some enzymes in plants that are involved in lignin synthesis and it is essential in several enzyme systems. It is also required in the process of photosynthesis, is essential in plant respiration, and assists in plant metabolism of carbohydrates and proteins

Molybdenum – regulation of plant functions and nitrogen nutrition

Nickel - nickel is a component of some plant enzymes, most notably urease, which metabolizes urea nitrogen into useable ammonia within the plant   

Smaller nutrients are essential for plants to carry out their metabolic, cellular, and growth activities, but they are not required in the same large quantities as the NPK major nutrients.

Top Tips

Tip 1: Spring is the ideal time to start fertilizing plants because that’s when their active growth period starts. It is not recommended to fertilize your plants during winter as this is usually when they go dormant. Fertilization will not benefit your plants during this time as they are not using their energy and nutrients as much as they would during their active grow period.

Tip 2: It’s better to under-fertilize your plants than over-fertilize them. Dilute your fertilizer (if concentrated). If the potting mix has a lack of nutrients and hasn't been fertilized in a while, you can make the fertilizer more effective by using less water when mixing it.

Tip 3: Plants that produce fruits or flowers will require more fertilizer than ones that do not. When fruits or flowers are picked those nutrients deplete and should be re-introduced via fertilizer.