Houseplant Soil – Building the Perfect Home

Your plant parenthood journey involves more than just watering and sunlight.

You also need to create the perfect home for your plants – which means identifying the ideal soil (or soilless mixture in many cases!) for your plant babies.

Each plant has its soil preferences; your job is to identify these needs using this indoor plant soil basics guide.

indoor plant soil basics

Our Promise:

By the end of this 4th lesson in our PLANT PARENT SUCCESS RECIPE SERIES, you will:

  • learn the role soil plays in your houseplant’s growth
  • understand how the type of soil affects the other levers in the Plant Parent Success Recipe (such as Watering, Humidity, and Pot selection)
  • understand the role of different growing mediums and their effect on your soil properties
  • gain the knowledge and confidence to create a custom indoor potting mix specific to your plant’s requirements.

Why is Soil Important for Houseplants?

Why is soil important for houseplants

Before we jump into what type of soil you should be growing your precious plants in, let’s take a step back and examine why soil is so important.

You may think that the only purpose of soil is to hold your plant up.

While you are correct that soil provides a support system for roots to anchor themselves and offer vertical support, it also serves as the delivery system for many other important elements. Such as:

  • Nutrient Supply – soil is one of the main sources of nutrients for indoor plants. It comprises various organic materials that hold and release essential elements like nitrogen, phosphorus, and potassium (NPK) that our beautiful plants require to grow and thrive.
  • Water Storage – most indoor plant potting mixes contain a medium to retain water, like moss. In the following sections, we’ll dive deeper into the various types of moss species and their benefits when we closely examine different mediums in potting mixes.
  • Beneficial Organisms – believe it or not, a tiny world exists in your houseplants’ pot. At least, there should be if you have set it up correctly. A healthy indoor plant’s soil should have a self-sustaining ecosystem made up of microorganisms and bacteria. They are critical in breaking down organic matter into nutrients (food) for your plants.
  • Temperature Insulation – Finally, soil also protects your plant’s roots from extreme temperatures in the surrounding environment.

How Does Soil Affect The Plant Parent Success Recipe?

Okay – we now know soil plays a variety of roles in supporting the healthy growth of our indoor plants. Let’s look at how the soil type affects the other levers of our Plant Parent Success Recipe.

To do that, we need to revisit the Recipe diagram.

indoor plant soil basics

GARDEN BENCH TOP TIP

If this is your first time reading about the Plant Parent Success Recipe, check out what it is about HERE.

How Does Soil Type Affect WATERING Your Houseplants?

Earlier in the Plant Parent Success Recipe series, we identified watering as one of the crucial skills every plant parent needs to master to keep their plants alive and healthy.

To master watering, you must understand how soil type affects the frequency of watering your indoor plants.

Spoiler Alert – it matters A LOT!

Let’s consider a common scenario:

Introducing Monstera to Home

Picture this: You’ve just brought home a gorgeous Monstera Deliciosa, ready to transform that empty, sunlit corner into a lush, leafy retreat. You’re armed with the care tag that cheerfully suggests “Medium water requirements.” You might think, “Great, I’ll just set my watering can to “medium”, and we’re set!”

If only it were that simple, right? ๐Ÿ˜Š

To be a successful plant parent, you’ve got to get down and dirty with your soil types.

Imagine you peek into your new Monstera’s pot and find it’s potted in a mix of sphagnum moss and standard potting soilโ€”both superstars at holding onto moisture like sponges.

If you stick to a “medium” watering schedule without testing the soil’s moisture level, you might accidentally water your plant when it’s not thirsty. And nobody likes soggy feet, especially not your Monstera, which could end up with dreaded root rot.

A savvy plant parent (with a recipe for success *hint-hint*) would first understand the properties of that soil type (in other words – it retains A LOT of water) and adjust their watering schedule accordingly.

They would also know to wait until the soil has mostly (or completely) dried before giving the plant more water – because they would have taken the time to understand and get to know your plant likes and dislikes during the PLANT AWARENESS section we stepped you through earlier in this Recipe Series.

So, our more seasoned plant parents might even consider giving their Monstera a new home in a chunkier, airier soil mix that’s just right for its needs.

However, changing the soil type can affect other interrelated factors – which is the perfect segue to the next section.

How Does Soil Type Affect HUMIDITY Around Your Houseplants?

Humidity and Soil Relationship

Continuing our Monstera Deliciosa scenario.

Suppose you repot your Monstera into a chunky, airy potting mixture.

This change can affect the humidity around your plant because, as we established at the beginning of the Plant Parent Success Recipe, many plant care factors are interrelated.

Swapping out the original mix of sphagnum moss and standard potting soil, which have excellent water retention properties, will reduce the moisture that evaporates into the air around your plant’s foliage.

By using soil that drains more quickly and retains less water, the humidity around the plant will correspondingly decrease.

This means you may have to supplement the loss of humidity with other sources like humidity trays (aka pebble trays) or installing a humidifier around your plant babies.

If you want to learn more about adjusting humidity for indoor plants, check out the humidity lesson in our Recipe Series.

How Does Soil Type Affect POT SELECTION for Your Houseplants?

Soil and Pot Selection Relationship

Your soil choice can also impact the pot you choose to grow your indoor plants.

Let’s consider how a Monstera’s growth can be affected by different combinations of soil and pot materials.

Chunky Aerated Soil:

A knowledgeable plant parent would know this soil type is designed to mimic the Monstera’s natural habitat, providing excellent drainage and airflow with ingredients such as orchid bark, perlite, and vermiculite.

Complementary Pot Pairings:

  • Plastic Pots: These are a good match because they retain moisture, which can offset the fast drainage of the aerated soil. This can be particularly useful in environments where the air is dry or if you’re prone to underwatering.
  • Glazed Ceramic Pots: With their reduced breathability, these pots can help maintain an even moisture level, balancing the quick-drying nature of the aerated mix. Ensure that the pot has adequate drainage holes to prevent waterlogging.

Regular Potting Mix:

With your the standard potting mixes you purchase from commercial nurseries, you will find they are designed to hold moisture while still providing adequate drainage.

Complementary Pot Pairings:

  • Terracotta Pots: These are ideal for a regular potting mix as they can help prevent overwatering by wicking away excess moisture due to their porous nature. This is especially helpful if you tend to overwater or if your environment is humid.
  • Plastic Pots: If you’re in a drier climate or your indoor air lacks humidity, plastic pots can complement a regular potting mix by reducing the frequency of watering needed.

Humus-Heavy Soil with Moss:

This soil mix is rich in organic matter and includes components like sphagnum moss, compost, and humus. It’s designed to retain more water and nutrients.

Complementary Pot Pairings:

  • Terracotta Pots: Since this soil type retains a lot of moisture, pairing it with a terracotta pot can help reduce the risk of overwatering by allowing excess moisture to escape through its walls.
  • Glazed Ceramic Pots with Added Drainage: If you choose a glazed ceramic pot, ensure it has enough drainage holes or add more. The goal is to balance the moisture-retentive properties of the soil with a pot that allows excess water to drain away to prevent root rot.

Hopefully, by now, you are starting to appreciate how each of the ingredients in the Plant Parent Success Recipe interact with one another.

For each soil type, it’s essential to consider the water needs of your Monstera and the environment it’s growing in. Chunky, aerated soils ensure that roots don’t sit in water but may require more frequent watering. Regular potting mixes are generally well-balanced and can be used with various pots, while humus-heavy mixes with moss are better for plants that need more consistent moisture but should be paired with pots that offer some moisture control.

Remember, regardless of the pot material you choose, drainage is key. Always ensure that your pots have drainage holes, and never let your Monstera sit in standing water, as this can lead to root rot and other health issues for the plant.

What Makes Up Potting Soil?

What Makes Up Potting Soil

Believe it or not, the perfect potting mix for indoor plants vastly differs from the soil in your backyard.

It can include a large variety of media. Each has specific properties that combine to make the perfect environment for your houseplants.

Here are some common materials used in indoor plant potting mixes.

Commercial Soil Brands

Commercial soil brands offer a range of potting mix options tailored to the specific needs of indoor plants. Each brand often has its proprietary blend of ingredients designed to optimize plant health and growth.

Here’s what you can typically expect from commercial soil brands:

  • Ready-to-Use: Most commercial potting mixes are pre-mixed and ready to use straight out of the bag, providing convenience for plant owners.
  • Consistency: These brands ensure a consistent product, meaning you can expect the same performance with each purchase.
  • Specialized Mixes: Many brands offer specialized soil blends for different types of plants, such as succulents, orchids, or acid-loving plants.
  • Added Nutrients: Some commercial mixes are enriched with fertilizers and other nutrients to give plants a good start without the immediate need for additional feeding.
  • Quality Control: Reputable brands often have quality control measures in place to ensure their soil is free from pests, diseases, and weed seeds.

Ideal for indoor plants such as:

  • A wide variety of houseplants
  • Seedlings and young plants
  • Plants requiring specific soil pH levels or nutrient compositions

Ready-made potting mixes are great for beginners because you can get into the hobby quickly and easily.

However, if you are looking to take your plant parenting skills to the next level, we’d suggest experimenting with your mixes and inventing your bespoke ratios specific to your environment using the following ingredients.

Moss

Sphagnum Moss

Moss is a staple in many indoor plant potting mixes. Its unique properties offer numerous benefits to houseplants, making it a go-to choice for gardeners and plant enthusiasts. Here’s a quick rundown of what moss brings to the table when used in indoor potting mixes:

  • Water Retention: Excellent for keeping the soil moist.
  • Aeration: Helps prevent soil compaction, allowing roots to breathe.
  • Texture: Contributes to a light and fluffy potting mix.
  • Acidity: Adds a touch of acidity for plants that prefer such conditions.
  • Nutrient Retention: Holds onto nutrients, reducing the need for frequent fertilization.

Ideal for plants like:

  • Moisture-seekers: ferns, African violets
  • Drainage-dependents: orchids, succulents
  • Acid-lovers: peace lilies, gardenias, azaleas

Perlite

Perlite is a popular ingredient in indoor plant potting mixes, and it offers several advantages for plant growth and health:

  • Aeration: Perlite enhances soil aeration, allowing roots to breathe and preventing soil compaction.
  • Drainage: It helps facilitate proper drainage, preventing waterlogging and root rot.
  • Lightweight Texture: Perlite keeps the potting mix light and airy, which promotes healthy root growth.
  • Neutral pH: It has a neutral pH, making it suitable for a wide range of indoor plants.
  • Longevity: Perlite does not decompose, so it provides long-term benefits to the potting mix.

Ideal for plants like:

  • Succulents: cacti, jade plants
  • Herbs: basil, rosemary
  • Tropical plants: pothos, spider plant

Garden Bench Top Tip

Try substituting pumice for perlite to achieve the same properties.

Vermiculite

Vermiculite

When it comes to preparing potting mixes for indoor plants, vermiculite is a valuable ingredient that offers multiple benefits for plant growth and health. Here’s a quick look at what vermiculite brings to the table:

  • Moisture Retention: Vermiculite excels at retaining moisture, ensuring that plant roots have a steady supply of water.
  • Aeration: It promotes soil aeration, fostering healthy root development and preventing soil compaction.
  • Nutrient Retention: Vermiculite can hold onto nutrients, gradually releasing them to nourish the plants.
  • pH Neutral: With a neutral pH, vermiculite is suitable for a wide range of indoor plants.
  • Lightweight Texture: It keeps the potting mix light and airy, facilitating optimal root growth.

Ideal for indoor plants such as:

  • Peace lilies
  • Philodendrons
  • Spider plants

Orchid Bark

Orchid bark is a key component for creating potting mixes tailored to the needs of certain indoor plants, particularly those that require well-draining conditions and a bit of structural support. Here’s an overview of the advantages orchid bark offers:

  • Drainage: Orchid bark pieces are excellent at improving drainage, reducing the risk of waterlogging and root rot in potted plants.
  • Aeration: The chunky nature of orchid bark allows air to circulate around the roots, which is essential for healthy root function and growth.
  • Root Support: Larger pieces of bark provide a sturdy structure that helps support plants with aerial roots or those that prefer to cling onto a natural substrate.
  • Longevity: Orchid bark breaks down slowly, ensuring that the potting mix remains loose and well-aerated over time.
  • Organic Material: As a natural, organic material, orchid bark gradually decomposes, contributing to the overall health of the soil ecosystem.

Ideal for indoor plants such as:

  • Orchids
  • Monsteras
  • Anthuriums

Incorporating orchid bark into your potting mix can mimic the natural growing conditions of epiphytic plants, which often grow on trees rather than in the soil. This makes it an excellent choice for plants that prefer drier roots between waterings and those that thrive in an environment similar to a tropical forest floor.

Worm Castings

Worm Castings

Worm castings, often called worm compost or vermicompost, are a highly nutritious soil amendment for indoor plants, offering many benefits that promote plant health and vigor. Below is a breakdown of the contributions worm castings make to potting mixes:

  • Nutrient-Rich: Worm castings are packed with essential nutrients, including nitrogen, phosphorus, and potassium, vital for plant growth.
  • Microbial Activity: The presence of beneficial microorganisms in worm castings helps break down organic matter into nutrients that are more easily absorbed by plant roots.
  • Improved Soil Structure: Worm castings enhance soil structure when added to potting mixes, creating a more hospitable environment for root development.
  • Moisture Control: They can hold water effectively, which can help regulate soil moisture levels and reduce the need for frequent watering.
  • Gentle on Roots: Unlike synthetic fertilizers, worm castings are gentle on plant roots, reducing the risk of chemical burns and providing a slow release of nutrients.

Ideal for indoor plants such as:

  • All houseplants (we love using it with all our plants ๐Ÿ˜‰)

By incorporating worm castings into your indoor plant potting mix, you can create a rich, organic, and sustainable environment that feeds your plants and improves the soil’s quality.

This makes worm castings an invaluable addition to the potting mix for various indoor plants and is the main reason why we have so many worm farms!

Coco Coir / Coco Coir Chips

Coco Coir

Coco coir, derived from the fibrous husks of coconuts, is a versatile medium that has gained popularity in indoor gardening. Available in various forms, including fine coir and chunkier chips, it offers several benefits for potting mixes:

  • Water Retention: Coco coir has excellent water-holding capacity, which helps to keep the soil moist and reduces the frequency of watering.
  • Aeration: Despite its ability to hold moisture, coco coir still promotes good aeration and drainage, preventing soil from becoming too dense or waterlogged.
  • Root Development: The texture of coco coir and coir chips encourages strong root growth, providing a supportive yet lightweight structure for roots to expand.
  • pH Neutral: Typically, coco coir is pH-neutral, making it suitable for various indoor plants without altering the soil acidity.
  • Sustainable: As a byproduct of the coconut industry, coco coir is a renewable and sustainable resource, offering an eco-friendly alternative to peat moss.

Ideal for indoor plants such as:

  • Aroids
  • Bromeliads
  • Succulents

When using coco coir or coco coir chips in your potting mix, you create an environment that closely replicates a plant’s natural conditions, particularly those that thrive in tropical climates.

It’s also well-suited for plants that benefit from evenly moist soil and those sensitive to overwatering, as the material allows excess water to drain away while maintaining adequate hydration.

Sand

Incorporating sand into indoor plant potting mixes can significantly improve the physical properties of the soil, particularly for plants that require excellent drainage. Here’s what sand contributes to a potting mix:

  • Drainage Enhancement: Coarse sand is particularly effective at increasing soil drainage, helping to prevent water from pooling around plant roots, which can lead to root rot.
  • Soil Structure: Sand particles create spaces within the soil for air and water to move through, which is essential for healthy root systems.
  • Weight and Stability: The weight of sand adds stability to potting mixes, which can be beneficial for top-heavy plants or those with substantial foliage.
  • Pest Deterrence: Certain pests, such as fungus gnats, are less likely to infest soils with a higher sand content due to improved drainage and drier soil surface.
  • Low Nutrient Content: Sand has minimal nutrient content, which allows gardeners to control the nutrient levels more precisely through supplemental feeding.

Ideal for indoor plants such as:

  • Cacti
  • Succulents
  • Bonsai

Coarse sand or horticultural sand is best, as fine sand can compact and reduce soil drainage. Sand is particularly useful for plants accustomed to arid environments or prefer their soil to dry out completely between waterings.

Charcoal

Horticultural charcoal, also known as activated charcoal, is a refined carbon form for gardening. It’s an excellent addition to potting mixes for indoor plants due to its unique properties and benefits:

  • Toxin Absorption: Activated charcoal can absorb and neutralize toxins, which can be beneficial in preventing the buildup of harmful substances in the soil.
  • Odor Control: It can help reduce odors by trapping and filtering out impurities and bacteria that may cause unpleasant smells in the potting mix.
  • Moisture Regulation: While it doesn’t retain water like other soil amendments, horticultural charcoal can help to improve the overall moisture balance within the potting mix.
  • Prevents Fungal Growth: The antibacterial and antifungal properties of charcoal make it a great addition to prevent the growth of mold and root rot in overly moist environments.
  • Aeration: Adding charcoal to the soil can improve aeration, providing a loose and porous structure that allows roots to breathe and grow freely.

Ideal for indoor plants such as:

  • Terrarium plants
  • Orchids
  • Container plants that are susceptible to overwatering or root rot

When incorporating horticultural charcoal into your potting mix, it’s usually used as a bottom layer in pots to assist with drainage and to keep the root zone healthy.

However, it can also be mixed throughout the soil to maximize its purifying properties. Charcoal is particularly useful in closed environments like terrariums, where moisture and bacteria can accumulate, or in any indoor setting where plant health is a priority.

NEXT UP in the Plant Parenting Success Recipe: Fertilizer

Okay, we must admit the soil section was much longer than we expected. However, that is understandable, given how important it is for the health and survival of your plant babies.

If you stuck it out with us – congratulations! You are already building up that Plant Parent resilience.

Next up in the Plant Parent Success Recipe is all things Fertilizer – an indoor planting skill that will really make your inside oasis thrive and shine!

NEXT: FEEDING YOUR HOUSEPLANTS THE RIGHT WAY