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A Guide to Using Slow-Release Fertilizers for Potted Plants

Slow-Release Fertilizer for Potted Plants

Slow-release fertilizer for potted plants releases nutrients into the soil gradually. It allows the plant to take up the nutrients when needed. This article highlights all you need to know about slow-release fertilizers.

What is a slow-release fertilizer?

Slow-release fertilizers gradually provide plants with necessary nutrients over an extended period. They can be organic or synthetic and are designed to release nutrients steadily.

Most slow-release fertilizers have a plastic resin or sulfur-based polymer coating, which breaks down under exposure to sunlight, heat, or water.

Quick-release fertilizers can cause damage to plants if not used properly, as they can be over-applied or not diluted correctly, resulting in “fertilizer burn.” Rain or watering can easily wash them out of the soil.

On the other hand, slow-release fertilizers reduce the risk of burning and stay in the soil for longer, providing a more consistent and steady supply of nutrients to plants.

Factors to consider when choosing slow-release fertilizer for your potted plants

Nutrient content

Ensure the fertilizer contains the nutrients for your plants, such as nitrogen, phosphorus, and potassium.

Release rate

Look for a fertilizer that releases nutrients at a consistent rate over some time. Most slow-release fertilizers are labeled with a percentage of the total nutrients immediately available, and the rest will be released over time.

Type of fertilizer

Slow-release fertilizers can come in different forms, such as granular, powdered or liquid. The form you choose will depend on your application method.

Plant type

Not all fertilizers are suitable for all plants, so choose a fertilizer appropriate for your growing plants.

Synthetic or organic

Slow-release fertilizers can either be organic or synthetic. While organic fertilizers are made from natural materials, synthetic fertilizers are chemical-based. Consider your preference and what best suits your garden needs.

Organic fertilizers

Organics Fertilizers for Potted Plants

Organic fertilizers comprise manure and compost. They also have products derived from animals, such as feather meals, bone meals, and blood meals. They break down gradually, allowing the plant to absorb the nutrients.

Pelletized coated fertilizers

Another common type of slow-release fertilizer for potted plants is pelletized coated fertilizer. They have a plastic shell or sulfur-coated urea that breaks down over time, releasing nutrients into the soil.

Environmental impact

Some fertilizers may contain ingredients that are harmful to the environment. Consider the impact of the fertilizer on the environment before making your final decision.

Types of slow-release fertilizer

There are several slow-release fertilizers, among them:

Controlled-release fertilizers

CRF, or controlled-release fertilizers, use a built-in mechanism to slowly-release nutrients over time rather than relying on environmental factors in the soil. It makes them a useful option for people who need to provide their plants with a steady food supply over a specific period.

Liquid fertilizer

Although not as widely used as fast-release liquid fertilizer, water-soluble slow-release nitrogen fertilizer is an option for those looking for a more gradual release of nutrients. These liquid formulations release nutrients at a slower rate than typical water-based fertilizers.

Granular fertilizer

Granular fertilizer is a type of water-insoluble fertilizer that is available as granules or pellets. It releases nutrients slowly over time. The solid structure of the granules or pellets helps prevent leaching, which is the loss of fertilizer because of runoff during watering or rain, by keeping them in the soil.

Common nutrients in best fertilizers for potted plants


Supplementing your plants with magnesium can improve the chlorophyll in their health. This mineral helps in the photosynthesis process.


Calcium helps plants grow strong and durable leaves, fruits, and flowers. Although it is not a primary ingredient in most fertilizers, it is often included in fertilizer mixtures.


Nitrogen is one of the most commonly used fertilizer ingredients, coming in different forms, such as ammonium nitrate and methylene urea. Nitrogen is essential for the growth and health of plants.


Potassium and potash, rich in potassium, can help plants resist pests and diseases. A proper level of potassium in fertilizer can improve the longevity of plants.


Phosphorus is a vital plant mineral. It aids the potted plant at every phase of its life, from seed, germination, root formation, and gradual growth.

Tips for applying slow-release fertilizer for potted plants

Consider the type of potted plant

First, you should consider the plant you are applying the fertilizer on. For example, avoid using lawn fertilizer on a hydrangeas and rhododendrons flower bed. As such, you should seek fertilizer suited for the specific plant.

Test your soil

Soil Testing

You can use an at-home testing kit to determine the nutrient content of your soil or send a sample to the agricultural department of a local university for testing. Review the results to find out if the soil naturally has high nitrogen, phosphorus, or potassium levels.

If the potting mix is high in a specific nutrient, you shouldn’t use fertilizer containing the nutrient. You can buy a test kit from your local store.

Choose organic fertilizer as it is eco-friendly

Choose slow-release fertilizers made with plant, animal, and mineral ingredients. For an environmentally friendly option, consider fertilizers that include fish emulsion and blood meal. And since it comes in water-insoluble pellets, they won’t dissolve when they come in contact with water.

Synthetic fertilizers are chemical-based and may include urea and ammonium nitrate. They work more quickly than organic fertilizers but also have a higher risk of causing damage to plants and vegetation. If possible, avoid them.

Select a well-balanced fertilizer

Look for a label on the fertilizer bag displaying three numbers separated by dashes. These show the fertilizer formula’s proportion of nitrogen, phosphorus, and potassium. Generally, most slow-release fertilizers for potted plants have the standard 3-1-2 ratio. Where possible, look for a fertilizer intended for the specific potted plant.

Choose the right longevity

Before buying a fertilizer, check the label to see the product’s duration to provide nutrients to your potted plant. Choose between 3-to4-month and 5-to-6-month fertilizers, depending on the type of the plant. Research shows that slow-release fertilizer can take up to 18 months to release all nutrients.

What are the benefits of using slow-release fertilizer?

  • You save money: Slow-release fertilizer for potted plants saves money and allows you to provide nutrients for up to three seasons.
  • Save time:Unlike liquid fertilizers that need frequent feeding, mixing, and buffering, slow-release fertilizer saves the grower’s time.
  • Save labor:You need little effort to apply slow-release fertilizers.
  • Reduced burn risk: Slow-release fertilizers are less likely to cause “fertilizer burn” (damage to plants caused by over-fertilization) than quick-release fertilizers.
  • Efficient release of nutrients: Slow-release fertilizers release nutrients over an extended period, allowing plants to take up nutrients as needed. This reduces the risk of nutrient loss through leaching or volatilization.

What are the signs of over-fertilization in potted plants?

Here are the most common signs of over-fertilization.

  • Fertilizer crust: It shows that the plant is not taking in the minerals, and they are accumulating on the surface of the soil.
  • Yellow, wilting leaves:Over-watering or inadequate light can also cause it, so it’s important to experiment and figure out the root cause.
  • Brown leaf tips:They suggest that the plant is not effectively taking in water, a sign of excessive fertilization.
  • Blackened roots:It is a sign of “fertilizer burning.”
  • Defoliation:Observe for leaves dropping off. It can also result from inadequate watering, so it is important to consider that.
  • Stunted growth: Plants require a proper proportion of nutrients to support their growth and metabolism. If there is no improvement, likely, the nutrients are not in balance.

How to cure an over-fertilized plant

Remove excess fertilizer

Removing the fertilizer on the plant or topsoil will stop further over-fertilization if you can see the fertilizer on the plant or topsoil. In addition, if the fertilizer salts have formed a crust (usually white), it also needs to be removed.

Leach the soil

Leaching helps move the plant fertilizer from the plant’s root system. It helps prevent further overfertilization, permitting the roots to heal. If possible, use distilled water.

Allow the water to drain

Allow the water to drain out the bottom. Repeat the process four times for optimal results to ensure excess fertilizer is washed away through the drainage holes.

Remove damaged foliage

Use a pair of scissors to cut off damaged leaves. It helps with the plant’s future health and prevents the accumulation of pests.


If possible, repot your plant after leaching soil in the old container. Repotting will help the roots heal, allowing the plant to rejuvenate.


Slow-release fertilizers for potted plants are no doubt better than conventional ones. They allow the plant to absorb the nutrient gradually while saving you time, labor, and time. Choose the right plant fertilizer based on the type of potted plant.

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