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Fertilizing in Fabric Grow Bags (Insights You Need to Know)

It is a well-known fact soil nutrients help the plant in your garden grow. One of the most common ways to supply those beneficial nutrients is fertilization. But how does the way you fertilize change when growing plants in a container? Today, we’ll explore that question and tell you everything you need to know about fertilizing in fabric grow bags.

Fertilizing in Fabric Grow Bags
Fertilizer is especially important when using grow bags

Fertilizing Plants in the Gound vs. Containers

Before discussing the best way to fertilize in a fabric grow bag, we need to point out one key difference between growing plants directly in the ground and growing them in containers. When you grow a plant in the ground, it can use nutrients already present in the soil, and those preexisting nutrients come from the many plants and animals that have decomposed over the years.

Plants that grow in the ground start with a larger supply of available nutrients. However, you won’t always know what nutrients are present and whether they will benefit the specific plant species you want to grow. That is why gardeners continue to amend their soil even though there are natural nutrients there already.

By contrast, containers do not inherently contain the soil nutrients your plants need. The reason for that is simple—when you first buy a garden container, there will be nothing in it at all. As a container gardener, it is your responsibility to fill your containers with a healthy growing medium.

Part of that initial process involves adding the right type and quantity of nutrients your plant needs. This aspect of container gardening means you’ll have to do a bit more work upfront. But it also means you’ll have greater control over the soil’s quality, allowing you to create the ideal growing conditions for your plants.

How to Fertilize When Using Fabric Grow Bags

Now that you know the fundamental difference between fertilizing plants in the ground versus those that live in containers, you are ready to learn the best process for fertilizing in fabric grow bags. This process is a lot like fertilizing in any other container, but there are some distinctions that we’ll soon point out.

Mix Slow-Release Fertilizer into the Soil from the Start

When filling a fabric grow bag, use a potting mix that contains a slow-release fertilizer. If your soil does not have a slow-release fertilizer already, you can mix it in yourself at this stage.

Slow-release fertilizers have a synthetic coating that breaks down over time. As it does, the fertilizer within releases into your soil to become a fuel source for your plants.

Including a slow-release fertilizer in your growing medium gives your plants the chance to thrive from the start. They also ensure that your plant will receive a steady supply of nutrients during the first few months of growth.  

Use Amendments to Enrich the Soil Further

Soil amendments are also an excellent way to increase the nutritional quality of the soil in your fabric grow bag. Organic materials like the ones below are all suitable options for this job:

Use the amendments above to add nutrients to your soil over the long term. When you include these materials, they will decompose over several seasons. As they do, they will further enrich your soil as they transform into nutrients that your plant will love. Another great option is to learn how to make organic living soil.

Apply Additional Fertilizer During the Growing Season

The slow-release fertilizer and the soil amendments you add to your fabric grow bags will not be enough. Since containers offer a limited space in which your plants can grow, it is easy for your plants to absorb all the available nutrients present in the soil. When that happens, your plant will run out of food and struggle to continue its growth.

To counteract that issue, you’ll need to continuously add fertilizer to the soil in your grow bag. The fertilizer you choose should match the unique needs of your plant. You should also apply that fertilizer according to a schedule that is appropriate for that plant species.

For ongoing fertilization, you can use additional slow-release fertilizer or quick-release fertilizer. Again, the plants you grow may prefer one or the other. Regardless of which you choose, you should know that fabric grow bags tend to need more fertilization than other container options.

Why Grow Bags May Need Fertilizer More Frequently

One of the greatest features of a fabric grow bag is its permeability. The walls of most fabric grow bags consists of a porous material that allows water to drain easily.

Other types of containers have a single drainage hole at the bottom or no hole at all. Those containers can trap water and let your plant’s roots become too wet. The permeability of a grow bag also makes for excellent aeration that traditional pots can’t give you.

However, that advantage comes at a slight cost. The permeability that makes for fantastic drainage can also allow fertilizer to escape the container. That means you may need to fertilize your fabric grow bag plants a bit more often than you would for a plant in a different kind of container.

With that said, fabric grow bags remain a superb option for any gardener. While they may call for a bit more fertilization, the benefits of fabric grow bags far outweigh their cons.

How to Choose the Right Fertilizer for Your Plants

Knowing how to fertilize plants in fabric grow bags is one part of the job. You’ll also need to understand how to choose the best type of fertilizer for your plants. That process begins with an understanding of what kind of nutrients a standard fertilizer contains.

Understand N-P-K Ratios

When you shop for fertilizer, you’ll notice that most options feature a set of three numbers on their packaging. Those three numbers are the NPK ratio, and they are crucial to understanding what that fertilizer will provide for your plants.

The letters N, P, and K stand for nitrogen, phosphorus, and potassium, the three macronutrients that your plant needs most. Here is what each of those nutrients does for a plant:

  • Nitrogen (N) – Encourages foliage growth
  • Phosphorus (P) – Supports root, fruit, and flower development
  • Potassium (K) – Helps plants grow strong stems

The number associated with each nutrient represents the percentage of that nutrient present in the fertilizer mix. You’ll find that many fertilizers have equal amounts of nitrogen, phosphorus, and potassium, while others offer these nutrients in different amounts.

Likewise, each plant species has different needs when it comes to these nutrients. While some plants will need a lot of nitrogen, others will prefer fertilizers that are heavy in phosphorus or potassium. Choosing the right one is a matter of knowing which plants you intend to grow and their certain fertilizer needs.

Micronutrients in Fertilizer

The last section pointed out the importance of the three macronutrients that plants need. However, there are some micronutrients that can help your plants as well. Plants sometimes need these nutrients in smaller quantities:

  • Boron (B)
  • Chlorine (Cl)
  • Copper (Cu)
  • Iron (Fe)
  • Manganese (Mn)
  • Molybdenum (Mo)
  • Zinc (Zn)

Most gardeners get by without worrying too much about micronutrients. But if your plant is struggling to grow, it may need some micronutrients to get it back on track.

Common Types of Fertilizer

Aside from the nutrient content, there are other ways to classify fertilizer options. One way to conduct that classification is by how quickly the fertilizer releases into the soil. In that regard, there are two primary options you’ll find:

  • Quick-release fertilizer – Provides readily available nutrients upon application
  • Slow-release fertilizer – Releases nutrients gradually over several weeks after application

Fertilizers also come in two main forms, each of which changes how you’ll apply your fertilizer. Here are the two options you find most often:

  • Granular fertilizer – A solid form of fertilizer that includes a synthetic coating, typically slow-release
  • Liquid fertilizer – Often quick-release, typically requires dilution

Adding granular fertilizer is as easy as sprinkling it on the soil then roughing the soil slightly to incorporate the granules. To use liquid fertilizer, you’ll usually need to mix it with water to dilute it then pour that mixture into the soil surrounding your plants.

Know What Your Plants Need

As has been alluded to throughout this article, finding the right fertilizer is all about knowing your plant’s growing requirements. Some plants will thrive on little to no fertilizer at all. Other plants will call for specific amounts of N, P, or K and will need to receive their fertilizer at a precise moment during the growing season.

Plants also have preferences for soil acidity. Using fertilizer is one way to raise or lower the pH of your soil as needed for your plants.

Fertilizing in Fabric Grow Bags: Final Thoughts

Fertilizing in fabric grow bags is a bit different than what you might be used to, but it is not at all difficult to do. Refer to the insights in the article above, and you’ll have no issue giving your plants the soil nutrients they need.

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