Container Gardening and Soil Amendments

Written by David S.

Container gardens can be quite lovely. They can be large or very tiny. What is essential to understand about creating a beautiful container garden is that these are artificial environments. That means that you design the soil to match the type of plants that will grow in the containers.

Example of Containers and Plants  

A bonsai tree is a single plant in a container. A clump of daffodils is a single type of plant group in a pot or container. A Boston fern in a hanging pot is another example of a single plant in a container. You can also mix many types of plants in a container – A variety of bulbs, ferns, annuals, perennials, etc. So long as each type of plant grows in the same environment, the plants should do well.

Soil Structure 

Different types of plants need different types of soil. Some grow in:

  • Poor soil – not a lot of nutrients, often sandy or very clay-like. These plants have evolutions that allow them to grow in challenging conditions. 
  • Loamy Soil – Rich in nutrients and organic matter. The forest floor in a large forest is an example. Loamy soil is created by nature in places where the humus layer is thick and the moisture level is high but not boggy. 
  • Well-draining soil – is sandy but may hold moisture or become arid. The soil in the desert is often well-draining, does not hold water, and the plants that live there are used to those conditions. 

 These are the basic soil structures and are often the goal that is required when planting a container garden or a pot full of flowers. In addition, we hear terms such as compost, potting mix, topsoil, and others that may be what we need or not. 

It is also essential to understand that bagged soil is not all created equal regardless of its name or type. For that reason, it is essential to understand the specifics when choosing soil. In addition, the types of plants you choose for that container will ultimately determine the type and quality of soil you need. 

Soil, pH, and Plants 

Soil pH is another big deal when creating the soil for a container. Some plants like very acidic soil – Azaleas are an example of an acid-loving plant – they like the pH in the 5.5 range. Another example of a pH-influenced plant is the hydrangeas, which like soil from 6.0-6.2. Not only do hydrangeas like acidic soil, but the color of their blooms also depends on the pH level of the soil. 

The pH of soil also affects plant health. For example, hydrangeas that grow in soil too neutral or alkaline may suffer from iron deficiency diseases. Therefore, when you choose soil for your container, be sure to check the pH. Some brands of soil have the same pH across all of their products. Others, such as EB Stone, may have specialty soil designed for plants within a specific pH zone. 

Soil and Mulch 

Sometimes these two terms are used interchangeably. However, soil and mulch are very different items. Soil feeds the plants, and while there is some nutrition in mulch, it is not enough to sustain a plant for long. Mulch is an attempt to recreate the humus layer of soil, but it is a poor attempt, and that is okay. 

Mulch has two purposes when it comes to landscaping. One purpose is to keep the soil from drying, so you use less water. The second purpose is to decorate the ground so your garden beds look nicer.   

Soil Amendments 

When creating the perfect growing environment for a container, you generally use soil amendments. You can think of soil amendments like the flavorings you add to a recipe to create a wonderful meal. A container full of beautiful plants is, after all, a feast for your eyes. 

Soil amendments change the quality of the soil. Above, we discussed different types of soils – well-draining, loamy, clay-like, etc. If you have clay soil and need it to be something different, you would amend it. The opposite of clay soil is sandy soil. One holds water, and the other lets water flow through it. So, soil amendments change soil quality on a physical level, nutrient level, and pH level. 

Soil amendments are a massive variety of products that you can choose to create the perfect growing environment. However, that mega selection can be intimidating if you are new to growing plants. The simple solution to overcoming that is to listen to the plants. Plants have specific needs. Some tips for growing successful containers include:

  1. It is choosing plants with similar needs – pH, food, light, watering, etc. 
  2. Create batches of soil that meet the needs of your plants – Use a bucket or garbage can to make larger batches of soil and then store the excess. When you store soil, the container should hold moisture and allow the soil to breathe. 
  3. Keep a recipe for the different soils you create. You want to be able to recreate the same growing environment again. A gardening journal is a handy tool. 
  4. Be specific in the types of soils you create. Make them specific for plant groups, such as orchids, bulbs, and succulents. 

Another essential piece of information is to know that there is a difference between meeting the basic needs of a plant and creating an environment where that plant will flourish. Happy plants produce beautiful blooms. Conversely, a plant that struggles to meet its basic need will have fewer flowers and bloom for only a short period. 

Keeping Container Soil Healthy 

We mentioned that a container of soil is an artificial environment. That means that you – the gardener – must maintain the soil quality as those conditions will not be duplicated naturally. In short, nature will not help you maintain the soil in your containers. 

Container soil needs to be amended at least yearly. However, amending the soil is a seasonal job for some plant species. There is a massive list of products that you can use to amend the soil. 

Amending the soil improves the soil nutrient levels rebuilds the soil structure so that it continues to have a proper pH and drainage – sandy soil, loamy soil, etc. The components of container soil decompose over time. For example, if there is perlite in the soil to improve drainage, it will decompose in a year, and the soil will begin to collapse – not drain. If you’ve grown a successful crop of bulbs, the soil nutrient level will drop, and the following spring will have fewer blooms. 

This means that you have to amend the soil to recreate that growing environment. You are in charge of the quality of the soil in each container. Green Thumb Nursery has a video that talks about soil amending products to learn more about this product. Just keep watching:

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