What Is The Best Soil for Indoor Plants? How Do You Choose It?

best-soil-for-indoor-plants

The best soil for any houseplant depends on its unique needs and the ingredients present in the soil mix. For example, cacti and succulents prefer well-draining soils with good aeration and moisture retention ingredients.

But what’s the best soil for indoor plants?
And how do you choose the right indoor potting soil? 

We’ll answer these questions and two related FAQs to help you out.  

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Let’s go.

How to Choose the Best Soil for Indoor Plants

A. Based on Indoor Plant Requirements

Here’s a quick look at different types of plants and their soil requirements:

  • Succulents and Cacti require coarse soil with good aeration. The soil needs some moisture retention while allowing excess water to drain quickly.
  • Orchids require fluffy soil (ideally a soilless potting mix) with good aeration, quick drainage, and an acidic soil pH. Orchids, especially epiphytes, are extremely sensitive to root rot and can’t tolerate wet roots.
  • African Violets are container plants that require loose, airy, and fast draining soil with a high organic matter content.
  • Tomatoes and vegetables require soil with essential plant nutrients, like nitrogen and potassium, and good nutrient and water retention.
  • Flowering plants require a balance of aeration, water drainage, and water retention. The media should have a suitable soil pH, depending on the type of flowering plant.
  • Seeds and shoots need a light and soilless mix that is moisture retentive, airy, and low in plant nutrients — which helps facilitate germination and root growth.

Read more about the different types of potting soil for growing plants.

B. Based on Ingredients

To help you determine which potting soil to go for and which ones to stay away from, let’s explore the various ingredients used in container gardening soil mixes:

1. Biochar

An unconventional ingredient, biochar is a revolutionary soil amendment useful for all types of plants. 

It offers an array of benefits for plant care, such as:

  • Improved soil aeration and drainage.
  • Enhanced water and nutrient retention.
  • Growth of soil microbes for better nutrient availability.
  • Increased soil pH levels and reduced soil acidity.
  • Promoting root growth and improving plant yields. 
  • Trapping atmospheric carbon dioxide in the soil to reduce its impact on global warming.

Looking for indoor potting soil that contains biochar? 
Meet Rosy Soil.

The Best Soil for Indoor Plants: Rosy Soil’s Indoor Potting Mix

Rosy’s Indoor Potting Mix is a special growing media designed by plant and soil scientists to support the growth of any houseplant. 

It’s made from consciously sourced and synthetic-free ingredients, like aged vegan compost, high-quality biochar, and root-boosting mycorrhizal fungi. The mix helps conserve nutrients and water, optimize drainage, and deliver essential plant nutrients.

So, it’s the perfect plant mix for: 

  • Tropicals
  • Philodendrons
  • Aroids
  • Pothos
  • Cacti and succulents
  • Ferns, and more 

The blend also has a negative carbon footprint, making it a healthy mix for your indoor plants and the planet.

2. Sphagnum Peat Moss/Peat Moss

A traditional ingredient in regular potting soil, peat moss helps:

  • Improve water retention in soil.
  • Enhance soil structure, aeration, and drainage.

But peat moss decays with time and causes soil compaction. It also decreases soil pH, thereby reducing nutrient availability.

What’s worse?
Its harvest leads to the destruction of peat bogs — causing significant greenhouse gas (GHG) emissions. And as peat moss takes thousands of years to replenish, it isn’t sustainable. 

That’s why countries like the UK are moving toward a ban on the sale of sphagnum peat moss in garden centers.

Read more about why you should use peat free potting soil.

3. Coco Coir

Coconut coir has gained much attention as a viable alternative to the non-renewable peat moss. 

It has greater moisture retention than peat moss and takes longer to decompose. Moreover, it improves soil aeration and drainage and doesn’t affect soil acidity due to its neutral pH.

However, the downside to coco coir is its high carbon footprint — its processing and transportation require high energy use and water consumption. It also has a high salt content, which hinders water absorption by plant roots.

4. Perlite

Perlite is a superheated volcanic glass that’s used as an all purpose potting soil amendment to:

  • Improve aeration and drainage in a soil mix.
  • Loosen the soil and prevent its compression from peat moss compaction.
  • Retain moisture and nutrients, making them available for plant roots.

However, as it decomposes over time, you’ll have to replace it periodically. And since perlite isn’t a renewable resource, its mining and processing make it an unsustainable material.

5. Pumice

Pumice, also called sponge rock, is often used as a soil conditioner in a succulent soil mix. 

It helps:

  • Improve aeration and drainage. 
  • Maintain soil stability. 
  • Capture moisture and nutrients for plants. 

But a 2021 study found that processing pumice requires heavy energy use, contributing to increased carbon dioxide emissions and global warming.

6. Vermiculite

Vermiculite, used in all purpose potting mixes, is pH neutral and doesn’t decompose. 

Its benefit for indoor plants includes:

  • Decreasing soil density and improving aeration.
  • Enhancing water and nutrient retention.

However, its heavy water retention makes it unsuitable for plants like lavender, which need their root system to stay dry.

Moreover, vermiculite requires energy-intensive mining and processing — making it an unsustainable resource. 

7. Sand

River sand is an inexpensive, reusable, and traditional amendment that:

  • Improves water drainage and prevents overwatering.
  • Breaks up heavy soils for improved aeration. 

It’s suitable for plants that prefer dry conditions, like cacti and succulents. 

But while this resource is plentiful, its excessive mining can alter river and coastal ecosystems, destroying the habitat of aquatic animals.

8. Wood Chips/Bark

Wood chips and bark come in different forms, including pine bark, fir bark(orchid bark), and hardwood bark.  

These materials help increase airflow and drainage in the soil. However, they may also cause the soil to dry quickly and increase soil acidity.

9. Fertilizer

Fertilizers are important for nurturing growing plants — providing essential nutrients like nitrogen, potassium, and phosphorus. 

Generally, two types of fertilizers are used in potting soils: 

A. Synthetic Fertilizer

Synthetic or chemical fertilizers offer quick nutrition to growing plants. 

They’re often formulated for specific plant needs but require regular reapplication, leading to soil acidification. This reduces the availability of soil organic matter and harms beneficial microbes. 

It also has a high carbon footprint since it releases greenhouse gases. In fact, synthetic fertilizers are one of the largest sources of GHG emissions from the global agricultural production sector.

Moreover, since synthetic fertilizers are water-soluble, they can leach into waterways (when used for outdoor plants) and lead to environmental pollution. 

B. Natural Fertilizer

Unlike synthetic fertilizers, natural fertilizers are made from animal or plant products. 

A common component of organic potting soil mixes, they improve the soil structure in the long run and support the growth of beneficial soil microbes.

Here are some commonly used natural fertilizers in organic potting soil:

  • Compost: Finished compost contains nutrients from decomposed organic material. It improves soil structure and supports outdoor and indoor plant growth. 
  • Vermicompost: This fertilizer contains essential plant nutrients and beneficial soil bacteria. It’s mostly made from worm castings, also called earthworm castings or black gold. 
  • Manure: This organic material shouldn’t be used directly for house plants or outdoor plants as it’s acidic and may have contaminants. However, aged or composted manure is safe for plants, albeit with fewer nutrients.
  • Others: Other organic potting mix ingredients used as plant food include fish emulsion, bone meal, wood ash, and kelp meal. 

Tip: Natural fertilizer combined with biochar creates an ideal solution for effective plant care.

2 FAQs About Indoor Plant Potting Soil

Here are the answers to common questions on potting soil for indoor plants:

1. Can You Use Garden Soil or Topsoil for a Houseplant?

Ideally, no. 

Gardening soil or topsoil is heavy and often contains plant pests, like weed seeds and fungus gnats. This can impact plant growth and cause root rot due to compaction.

2. What to do with Old Houseplant Soil?

You can reuse your old houseplant soil for gardening by rejuvenating it with fresh soil. Alternatively, you could add fertilizers and amendments, like finished compost, to improve the indoor soil structure and nutrient levels.

But you should throw away diseased soil before it contaminates other house plants. 

Wrapping Up

The best potting soil for your potted plant ultimately depends on your plants’ needs.  

If you’re looking for an effective, earth-positive soil mix suitable for various container plants, you could give Rosy’s Indoor Potting Mix a shot.

Why not try a bag today to see the wholesome benefits it brings to your indoor plants? 

Sources:

Perlite vs Vermiculite: What Are The Differences?   
Organic Farming: Are Our Alternatives Actually Sustainable? 
Sand mining: the global environmental crisis you've probably never heard of 
New research shows 50-year binge on chemical fertilisers must end to address the climate crisis 

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