Understanding Soil Amendments: A Guide to Improving Your Plant's Soil

Having indoor houseplants can be a great way to add some natural beauty to your home but growing them successfully requires more than just watering them occasionally. One of the key factors that can affect the health of your indoor plants is the quality of the soil they are planted in. To ensure that your plants have the right growing conditions, it's essential to choose the right soil amendments for them.
The foundation of every plant is the soil. Since plants are native to many different environments such as the swamp, desert, rain forest, etc., this means they each have different soil substrates as well. Soil amendments are any materials added to the soil to improve its abilities such as aeration, water retention, soil drainage, and more.
There are a few things to consider when deciding which soil amendments are right for your plant:
  1. Longevity of amendment
  2. Soil texture
  3. Soil salinity and pH
  4. Plant sensitivities and requirements
With the right soil mix, your indoor houseplants will thrive and grow to their full potential. Let’s discuss different soil amendments and their benefits.

Soil Amendments

  1. Coco Coir: a byproduct of coconut fiber and husks, and it's an excellent and sustainable alternative to peat moss. Coco coir retains water well, making it ideal for plants that require moist soil. It is also an ideal amendment to improve soil aeration due to the natural texture of the coco coir. Additionally, it has a neutral pH and is naturally free of pathogens, making it a safe choice for indoor houseplants. Coco coir also breaks down much slower than peat moss and although more expensive than peat, it can be cleaned and reused! Making it an even less wasteful material to use for your plants.
  2. Sphagnum Moss and Sphagnum Peat Moss: Luckily, we wrote an entire article discussing the difference between Sphagnum Moss and Sphagnum Peat Moss and what their purposes are. You can find that blog by clicking here. In summary,

a. Sphagnum Peat Moss (Peat Moss): Peat moss is a popular soil amendment that is known for its water retention properties. It can hold up to 20 times its weight in water, making it ideal for plants that need a moist environment. However, it's not a sustainable option, and harvesting it can be harmful to the environment.

b. Sphagnum Moss: a type of moss that grows on the surface of soil or swamp. It has pliable, long spongy fibers that give it a soft and fluffy texture. Sphagnum moss is commonly used as a soil amendment because of its excellent water retention properties. It can hold up to 20 times its weight in water, making it ideal for plants that require a moist environment. Harvesting Sphagnum moss has less environmental impact as it is typically carefully harvested in order to ensure the approximate 5-6 years regeneration cycle.

  1. Horticultural Sand: Many succulents and cacti prefer sandy soil mixes. Horticultural sand is specially washed and graded for use in gardening and can come in various materials such as quartz, sandstone, or granite. These materials are lime-free thereby not affecting the pH balance of the soil. The roundness of the sad granules helps increase soil aeration allowing oxygen to flow to the roots. Horticultural sand does not clump together like traditional sand because of the sharp edges of the various materials. Be sure to add sufficient horticultural sand to clay soils as having too little will cause the soil to compact.
  2. Perlite: a volcanic rock that has been expanded by heat treatment. Perlite naturally expands making it lightweight and porous thereby proving excellent drainage for indoor houseplants. The shape and size of these granules also helps to aerate the soil, which is essential for healthy plant roots. Additional benefits include a long longevity, sterile, and its neutral in pH so it doesn’t disturb the pH of the soil. Lastly, perlite can be a great growing medium for germinating or rooting plants because of its natural abilities to sustain healthy and new roots.
  3. Vermiculite: Much like perlite, vermiculite is a lightweight mineral that is heated to high temperatures to make the granules expand. Specifically, vermiculite is a flaky, hydrated magnesium iron aluminum silicate mineral, typically varying in color from dark gray to sandy brown. Vermiculite is best used for moisture-loving plants, like ferns, as it has higher water retention properties than perlite. Just like perlite, vermiculite improves aeration of the soil and can also be used as an excellent medium for germination or rooting of plants. Additionally, if you have a top-heavy plant, using vermiculite instead of perlite is ideal since it is heavier and can help stabilize the plant to keep from falling over. One con to vermiculite is it is more expensive than perlite.
  4. Pumice: is a light-colored, extremely porous volcanic rock which forms during the explosions of volcanic eruptions. The rapid cooling of the gas-rich magma causes gas bubbles to be trapped in the rock from cooling too rapidly, thereby forming an amorphous volcanic glass. Pumice is another lightweight mineral that can be added to your plants soil mix to improve soil aeration. It is excellent at retaining oxygen, making it an ideal amendment for heavy or poor-draining soil. Pumice is not used for water retention as it has low retention qualities due to its large porous nature. Instead, pumice is used to help drain water from the soil thereby improving soil drainage.
  5. Sulfur and Lime: natural minerals added to soil mixes to adjust soil pH. Sulfur is added to lower soil pH, making the soil more acidic. Lime is added to raise the soil’s pH, making the soil more alkaline. If the goal is to make the soil more acidic, sulfur is the better alternative to peat moss, which is not a sustainably harvested material.
  6. Horticultural Bark: Bark mixes are typically composed of bark from pine and/or fir trees. You may also come across orchid bark which is usually composed of bark as well as small amounts of sphagnum moss, perlite, and/or coconut husk chips. Due to the shape and size of bark, it aids in preventing compaction of your soil and improves air circulation around the roots. Bark also retains moisture well so adding to a soil mixture will improve the soil's water retention Some people also used bark as a decorative cover for their soil. A downfall to using bark is it decays over time so your soil mix will eventually need to be changed. Bark is also a sustainable option and using it can help to reduce waste.
  7. Horticultural Charcoal: unprocessed carbon formed by thermal decomposition of organic materials. The natural shape of the charcoal helps drain excess moisture and is an amazing filter for removing toxins from the soil. Because of this, horticultural charcoal helps prevent soil-borne diseases and the buildup of minerals in the soil. The aeration this material supplies enhances soil structure, encouraging plant growth by providing ample room for roots to grow and thrive. Horticultural charcoal also helps prolong longevity of soil mix by balancing pH level of the soil. Charcoal’s natural abilities help keep the soil's pH over 7.0, making it more alkaline than acidic.
  8. Worm Castings: an organic fertilizer formed from the waste of earthworms. As the earthworms eat and move through compost, they digest and break down complex nutrients and excrete nutrients into a form able to be absorbed by the plant's roots. These nutrients are slowly released into the soil making it a safe and gentle natural fertilizer. Worm castings are also super effective at repelling pests such as aphids and spider mites. Worm castings also improve soil structure by increasing aeration, improving drainage, and enhancing moisture retention all at the same time! Producing your own worm castings from composting is also a sustainable practice that reduces the amount of food and garden waste that ends up in landfills.
  9. Natural Fertilizers: Such as compost, fish emulsion, and bone meal, are excellent choices for providing essential nutrients to indoor houseplants. They are also organic and sustainable, which means they are free of synthetic chemicals and safer for the environment.

In Summary




Coco coir, perlite, vermiculite, pumice, bark, horticultural charcoal, worm castings

Water Retention

Coco coir, peat moss, sphagnum moss, vermiculite, bark, worm castings

Excess Drainage

Perlite, vermiculite, pumice, bark, horticultural charcoal, worm castings

Soil Structure

Coco coir, perlite, vermiculite, pumice, bark, horticultural charcoal

Removes Toxins/Mineral Build-up

Horticultural charcoal

Increases soil pH (alkaline)


Decreases Soil pH (acidic)

Peat Moss, sulfur

Neutral pH

Coco coir, sphagnum moss, perlite, horticultural charcoal (balances pH)

Natural Fertilizer

Worm castings, bone meal, compost, fish emulsion

Pest Repellent

Coco coir, worm castings


Understanding the different types of soil amendments and their purposes is crucial for achieving healthy and thriving plants. Soil amendments can transform your indoor garden by improving soil quality, increasing nutrients, and promoting plant growth. Whether you choose a sustainable option like coco coir or bark, or a mineral-based amendment like perlite or vermiculite, each soil amendment has its unique benefits. So, research what your plants needs to succeed and experiment with different soil mixes to find the one that works for your houseplants.

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