Perlite vs Vermiculite

Perlite vs Vermiculite

What is Perlite?

Perlite is a naturally occurring mineral and a kind of volcanic glass. When obsidian glass from a volcano becomes saturated with water over a long period of time, perlite is formed.

This mineral has a pH between 6.6 and 7.5, is completely odorless, clean, easily handled and lightweight. Not every kind of volcanic glass can become perlite. The formation of the mineral is only possible when obsidian comes into contact with water.

The result is the creation of a unique volcanic glass containing a high content of water. As heat is applied to the substance by the manufacturer, the mineral puffs up and transforms into small, white balls.


In many instances, the little white balls or perlite are mixed into potting soils. This is what adds water retention and soil aeration to your soil. In addition to the retention of some water, the air is retained on the surface.

This is possible due to the nooks and crannies in the little balls. If the plants in your garden need to completely dry out before you water them, perlite is the ideal choice.

A good example is if you are growing succulents or cactuses, we recommend adding this mineral to your soil. Due to the porous nature of perlite, expect any excess water to drain away quickly.

You can easily crush the substance between your fingers into a powder. This is not considered an issue since this type of pressure is not present in your beds or pots. The main purpose of perlite is to improve the aeration of your soil.

The other uses include providing better oxygen access and drainage to the roots of your plants and lightening your soil. Perlite is an excellent choice for creating your own soil mix for potting or mixtures to start seeds. The benefits include:

  • Neutral pH level
  • Holds nutrients
  • Non-toxic, odorless, sterile and clean
  • Helps to lighten compacted or heavy soil
  • Lightweight enough to work as a substitute for sand
  • Holds between three and four times its weight when placed in water
  • Six percent water is contained in the granular, white pieces
  • Due to the lightweight nature, perlite floats to the top of your plant containers
  • Will not mold or rot
Seed Starting Mixes

Seed Starting Mixes

What is Vermiculite?

The term vermiculite is in reference to a group of aluminum-iron magnesium silicates or hydrated laminar minerals closely resembling the appearance of mica. When in your soil, this silicate will interact with magnesium, calcium and potassium.

The substance helps slightly raise your plant's pH despite the neutral pH of 7.0. The mineral is created using either a silicate material or compressed dry flakes both spongy and absorbent.

The color ranges between dark brown and golden brown. Once mixed, it can be difficult to determine what is your potting soil and what is vermiculite. When you add water, the expansion of the flakes forms a shape similar to a worm.


You will most likely be tempted to poke the little worm shapes with your fingers. Many people do the first time they see vermiculite. If your plants need damp soil that will not dry out, we recommend vermiculite as your best option.

If your plants require a lot of water, use this substance. We have found the easiest way to do this is by taking a healthy scoop of vermiculite and mixing it with your potting soil.

Once you add water, the substance will absorb between three and four times its volume. Be aware your pots will become a little bit heavier than before. Since the absorption is similar to a sponge, more water will be absorbed than with perlite.

This means your soil will not be as well aerated and the roots of your plants will have less oxygen. We do not recommend growing plants in this substance if damp soil is not required or it can lead to root rot.

You need to know the needs of your plants to determine how water-retentive your soil should be. The benefits of vermiculite include:

  • Excellent to blend custom potting mix for your soil
  • Provides your plants with nutrients while retaining moisture in your soil
  • Easily mixes with your soil
  • Recommended for seed starting
  • Odorless, non-toxic, sterile and clean
  • Helps lighten compacted, heavy and loose soil types
Best Soil Test Kits

Best Soil Test Kits

Commonalities Between Vermiculite and Perlite

Both substances are lightweight. You can use either one to create mixtures for soilless potting. This will improve the texture and aeration in your garden and potting soil mixtures.

Both substances are sterile, odorless, seed-free, insect-free and disease-free. Neither one will decompose, deteriorate or rot. You can use both for soilless potting mixtures to cultivate your plants.

Both mediums are suitable for seed germination, hydroponics, transplants, propagation and containers. We frequently use both as carriers for herbicides, pesticides and fertilizers to improve our coverage.

You can use both substances in your garden to increase the retention of moisture, prevent your soil from compacting and improve drainage. Both are suitable for cultivation, seed starting, propagating new plants and composting.

Both mediums also work well for outdoor growing and indoor growing, but there are differences as well.

Perlite vs Vermiculite

Differences Between Vermiculite and Perlite

The main difference between vermiculite and perlite is how each one retains water in addition to the amount of water each substance can retain. This means both are appropriate for different substances.

We recommend vermiculite if your plants require a lot of water such as forget-me-nots and certain types of irises. For plants requiring a lot of water, perlite will dry out your soil too quickly.

Vermiculite holds too much water for certain plants including rhododendrons, succulents and cacti. These plants require well-draining soil. If you use this substance, there is a good chance your plants will suffer from root rot or die.

Both are capable of retaining water. The difference is vermiculate is a lot like a sponge and holds more water than perlite. Your plant roots will not receive as much aeration.

Due to the nooks and crannies, perlite has a larger surface for water storage. Your soil aeration improves because the excess water drains away easily.

Countertop Compost Bins

Countertop Compost Bins

The Composition

When manufactured for horticultural use, heat is applied to vermiculite for an expansion of the particles. This means when you use the substance as a potting medium, it will absorb more moisture.

When water is added to vermiculite, it can absorb between three and four times its volume in addition to attracting plant nutrients including phosphorus, calcium, magnesium and potassium.

As a type of volcanic rock, perlite is rich in sodium. When the substance is mined to be used for potting, the perlite is crushed. Heat is then applied for an expansion of the particles.

The granules contain microscopic bubbles capable of holding and absorbing water in addition to holding air.

Uses for Horticulture

You can use either substance in your garden to retain moisture, improve aeration and prevent your soil from compacting. We have found both effective for seed cultivation, new plants, lawns, composting and growing containers indoors.

Due to the amount of water retained by each substance and the way the water is retained, they are appropriate for different types of plants. If your plants require a lot of water, vermiculite is ideal.

Plants needing plenty of water will dry out quickly if you use perlite. This makes vermiculite great for plants requiring well-drained soil like cactuses. Vermiculite retains too much moisture for certain plants resulting in root rot or death.

Perlite vs Vermiculite

Can Vermiculite and Perlite be Mixed?

You do not need to mix these two substances since each one is suited for different types of plants and situations. We recommend perlite for growing epiphytes, succulents, cacti or any plants requiring a lot of aeration and fast-draining soil.

If your plants need a humidity boost, perlite is a good option. Vermiculite is more appropriate if you are starting seeds or your plants consistently need moisture from the soil.

Which One Should I Use in My Garden?

The gardening community is always having discussions about whether perlite or vermiculite is better for the garden. The truth is you can use both since each one has specific purposes. You should use perlite when:

  • There is clay soil in your garden you need to loosen.
  • Your seedlings are being moved to separate plots.
  • Your plants need to be completely dry before you water them again.

When you add perlite to clay soils, puddles and surface crusting can be completely eliminated. The substance helps decrease soil temperature fluctuations within your garden soil.

You can also improve both aeration and drainage by using perlite for your home garden. Depending on what you are using it for, you can purchase horticultural perlite in different grades.

If you just need a general application, we recommend using a fine to medium grade. It is sterile, free of disease and free of weeds. You should use vermiculite when:

  • You require an additive to ensure your plants remain moist.
  • You want strong seedlings to develop in your seed trays.

You can purchase vermiculite in horticultural bags. You will receive directions on how to work the odorless substance into the soil of your garden. Since this soil conditioner is permanent, it will not break down like compost.

When it rains or you water your garden, the substance will hold water within your soil, It will not be released until your soil starts to dry out. You can also use vermiculite for composting, lawns of for potted containers.

You can also use vermiculite to study funguses such as mushrooms. It will improve soil requiring an additive for water retention when you have plants that need it.