Soil is the foundation of healthy plant growth. Getting the right mix is crucial, especially for indoor plants where ideal growing conditions are harder to achieve. While many premade potting mixes are available, making your own can be more cost-effective and tailored to your plants’ specific needs.
Having experimented with various soils and mixes over the years, I’d like to share my insights to help you succeed with your indoor plants.
Potting Soil vs Potting Mix
You might be wondering what the difference is between potting soil and potting mix. Technically, potting mix is a soilless blend containing ingredients like coconut coir and perlite. Potting soil, on the other hand, includes organic matter such as soil or compost. These terms are often mixed up, but the important thing is the ingredients and their ratios.
Making a Potting Soil/Mix for Indoor Plants
When making a mix for your plants, the first step is understanding the conditions your plant grows in in its natural environment. Some plants like their roots to dry out , others like constantly moist or even wet conditions.
Soil Properties
Aeration and Drainage
Generally, most plants prefer a state of constant moisture, on the verge of drying out but not quite. Very wet root systems cannot get oxygen unless the plant has specific adaptations (e.g., swamp plants). This can lead to root rot and plant death. Therefore, it’s crucial to identify if your plant needs a dry, wet, or moist soil and implement accordingly.
Anything with large particles will help create a light mix and allow for good aeration and drainage such as:
- Sand
- Perlite
- Bark
- Wood Chips
Moisture Retention
Plants use water throughout the day to absorb nutrients and hydrate their leaves. A soil that holds moisture means water is available whenever the plant needs it. However, overwatering is a common issue that can lead to yellow or brown leaves and plant death.
When selecting ingredients for a potting mix, consider how often you want to water your plants. A heavy mix made with more soil will retain water longer, whereas a lighter mix will need more frequent watering as the water will drain out of the pot quickly. This is an important factor to consider when making a potting mix for your plants.
It’s usually better to err on the side of caution and opt for a lighter mix, as overwatering is a common cause of yellow or brown leaves and plant death. Make sure to adjust your watering routine if you use a mix with high moisture retention.
Ingredients that can be used for moisture retention include:
- Sphagnum Moss
- Coconut Coir
- Vermiculite
- Peat Moss
- Clay
Nutrient Content
Plants need nutrients to grow and stay healthy, much like humans do. In the wild, they mainly get their nutrients by absorbing water that has dissolved minerals from the soil. These minerals are deposited in the soil over time as rocks and organic materials break down.
The amount of nutrients available to plants from the soil depends on factors such as pH and soil composition. A potting mix rich in soil and organic matter will provide lots of nutrients, whereas a mix containing ingredients like coconut coir and sand will have fewer minerals available.
If you’re using a light mix, you will need to supplement your plants’ nutrient intake by adding liquid or granular fertilizers. I usually mix a liquid fertilizer with water and apply it every other time I water my plants.
pH Balance
pH is important for plants because it affects how they absorb nutrients. At different pH levels, various minerals become either locked up or available for the plant to absorb. Plants that require specific pH levels have adapted to these conditions in their native soils.
Most plants prefer a neutral or slightly acidic pH, which is commonly found in most soils and commercial potting mixes. Adding organic matter typically makes the soil more acidic, but it generally remains relatively neutral and doesn’t lead to over-acidification.
If a plant requires more acidic or alkaline soil, larger adjustments are necessary. Adding sulfur is the most common way to lower pH, while adding dolomitic lime is a common method to increase alkalinity.
In general, you won’t need to adjust the pH unless you are growing a plant with really specific pH requirements.
Optimizing Plant Growing Conditions
Light Requirements
When plants grow in a high light environment, several things happen. Firstly, increased light means faster growth, and faster growth requires more nutrients from the soil. As we just talked about, plants use water to absorb the nutrients they need.
Plants also lose moisture through pores on their leaves, similar to us when we sweat. When you see a plant wilting and curling its leaves in hot weather, it is trying to reduce its leaf size and decrease evaporation.
Additionally, soil exposed to light will dry out faster than soil in the shade. These factors are important to consider, as plants in bright light will dry out more quickly.
Watering Frequency
By now, we can see how everything fits together. Plants in a light mix or bright light will require more frequent watering, while those in a heavier mix or shade will need much less watering. You should experiment with soil composition, plant requirements, and your routine to determine the best watering frequency for your plants.
If you think your plant might need repotting to better suit its growing conditions, check out my guide on how to repot a plant successfully. This will provide you with the knowledge and confidence to repot your plants with ease.
Humidity
In very humid conditions, your soil may develop some fungal problems and so you might opt for a lighter soil mix if that’s a concern. However in my experience humidity isn’t going to play much of a role at all in deciding what kind of potting mix to use.
DIY Potting Mix for Indoor Plants
I like to use the same potting soil recipe for all my plants. It simplifies the mixing process and ensures consistent soil conditions for watering. Buying ingredients in bulk and mixing them myself is cost-effective and allows customization for my specific needs.
Ingredients:
- 2 parts coconut coir
- 1 part perlite
- 2 parts premium potting mix
Benefits of This Mix:
- Coconut Coir: This sustainable ingredient retains moisture while allowing good drainage and aeration. It has a neutral pH and is cost-effective. Its use helps make the mix less dense, reducing the risk of soggy soil and root rot.
- Perlite: Enhances aeration and drainage, preventing soil compaction and ensuring your plants’ roots have access to oxygen. It is also very lightweight.
- Premium Potting Mix: Provides essential nutrients and beneficial microbes, promoting healthy plant growth. I tend to use ones that have granular fertilizers included in them.
This is a low fuss, one size fits all mix for most indoor plants (works outside too). By drawing on the strengths of each ingredient, this mix ensures your plants receive balanced moisture retention, aeration, and nutrients.
If you’re also interested in designing and selecting the right indoor plants for your space, my guide on indoor plant design and selection tips may be useful for you.
Adjust the proportions as needed based on your specific plant requirements. that will keep your plants moist for a week or two before you need to water again depending on your conditions.
Custom Mixes for Specific Plants
Succulents and Cacti:
- 2 parts sand or perlite
- 1 part peat moss or coconut coir
- 1 part garden soil or potting soil
Orchids:
- 2 parts pine bark
- 1 part perlite
- 1 part sphagnum moss
African Violets:
- 1 part peat moss
- 1 part vermiculite
- 1 part perlite
Conclusion
Creating the best potting soil for indoor plants involves understanding the conditions your plant lives in, it’s needs and customising the mix to suit. The potting mix I’ve shared is a versatile, low-fuss solution suitable for most indoor plants. Experiment with the proportions and your watering routine to find what works best for your specific conditions.
When you have Indoor plants, at some point its inevitable to get pests like fungus gnats. If you’re looking for a solution, my article on how to get rid of fungus gnats provides effective solutions to help you get rid of them effectively.
Do you have a favourite potting mix recipe? Share your best mixes in the comments below and let’s help each other grow healthier, happier plants!
