Understanding The Different Types of Fertilizers

Apart from the content of different fertilizers, i.e., the ratio and combination of macro and micro-nutrients, there are several different delivery systems for the fertilizers to get their nutrients to the plants. Here’s a list of the primary types of delivery systems for plant fertilizers;

• Release-Based;
  • Controlled-Release: Controlled-release fertilizers are coated with materials that control how quickly the nutrients are released. This level of control offers several advantages including minimizing the likelihood of high initial salt levels in the potting mix, continued availability of nutrients over a long period of time, and the reduction of nutrient losses when top-dressed since the nutrients have to run through the potting medium which increases the chances they are absorbed by the plant.
  • Slow-Release: Slow-release fertilizers can take months or even years to release their nutrients, and differ from controlled-release fertilizers in that the release rate depends on factors that are not within anyone’s control, including potting mix and area moisture levels, microorganisms, pH levels, temperatures, and surface area.
• Liquid: Liquid fertilizers are diluted with water and applied through watering. They are quickly absorbed by the plant and often used during the growing months (summer) given their ability to quickly replace nutrients used up by the plant during periods of rapid growth.
• Granular: Granular fertilizers are sprinkled on top of the potting mix and then mixed in through watering. The challenge with granular fertilizers is that it’s easy to over-apply them which can burn plant roots.

For most houseplant owners, slow-release or liquid fertilizer work best and are easy to manage with minimal effort.

💚 Pro-tip – choose organic over synthetic fertilizers and look for OMRI certification if possible. OMRI is the Organic Materials Review Institute and OMRI-listed products have been checked for prohibited ingredients while using approved manufacturing processes.