Pumice vs. Perlite: Which Growing Medium is Better?

Introduction

Pumice vs. perlite, when do you use either one?

Both are excellent soil amendments in hydroponic gardening.

Outside of hydroponics, many gardeners mix these pebble-like materials with potting soil to improve soil drainage.

Furthermore, pumice and perlite are favorite choices among succulent lovers because these materials do not retain excess water, which can cause root rot.

Root rot is a precursor to the death of the plant.

Other than root rot, drainage problems in the soil cause waterlogged conditions that can further cause fungal infections in the root system. 

That’s why plants rooted in these soils can be susceptible to diseases and may die because of severe infections.

However, many growers and gardeners often get confused when choosing between perlite and pumice because they do not know the basic differences.

In this blog post, we will discuss the characteristics of perlite and pumice and contrast their differences.

What is Perlite?

what-is-perlite

Perlite, also called sponge rock, is a mineral that is made mainly from volcanic glass.

It contains around 70% silicon dioxide and other minerals, such as potassium oxide, sodium oxide, aluminum oxide, and iron oxide. 

In nature, the combination of these minerals can be recognized by their colors, which can be either black or dark gray. 

However, before the perlite can become a usable gardening material, the raw perlite is processed with pressure and heat above 1700-degrees Fahrenheit.

This process continues until the minerals burst and expand up to 15 times more than their initial volume. 

Before this heating process, the colors of perlite were generally blue, green, red, gray, or brown.

The final product looks like a whitish porous ball. You might recognize perlite by the white specs that are in your potting soil.

There are three basic sizes of processed perlite: coarse, medium, and fine. Obviously, you should choose the size based on what you need. 

Some gardeners have a mixture of all three sizes in their potting soil.

However, perlite is predominately used in hydroponics gardening or as a succulent soil mix. The reason is that perlite improves the aeration capacity of the soil.

The downside of perlite is the fine particles that it creates. Perlite dust can be problematic and unhealthy for your respiratory system [1]. 

If you are handling a large amount of perlite, wear a mask to protect yourself from the fine particles of perlite.

Advantages

There are many advantages to the use of perlite, which are:

  • Inexpensive
  • Lightweight
  • Various sizes are available
  • Improves the air circulation and aeration of other growing media

Disadvantages

While there are a handful of advantages to perlite, there is also a disadvantage to it:

  • It produces hazardous dust particles

What is Pumice?

what-is-pumice

Like perlite, pumice is also an ideal soil additive and comes from volcanic rock. It is a naturally lightweight rock.

Pumice is different from perlite minerals because it is a lightweight, porous rock that forms after the rapid cooling of the lava after explosive volcanic eruptions.

When the lava begins to cool, its chemical properties change, entrapping tiny gas bubbles that dissolve. 

This combination of cooling and chemical change creates a lightweight, porous mineral rock called pumice. Hence, its other name is “solidified rock foam.”

This soil amendment is dark gray to white in its natural state, depending on where the pumice was mined from. 

The mining process is considered environmentally friendly because pumice mining does not require any destructive processes like blasting.

Alternative Uses of Pumice

Many growers use horticultural pumice as a mulching material, also known as top-dressing, to decorate the gardens.

With its aerating properties, pumice provides air circulation in most types of soils.

Pumice also has insulating characteristics and is thus used in construction.

Advantages

Now that you know more about pumice, you may be wondering what advantages using pumice might bring to your garden.

  • Environmentally friendly
  • Less processing
  • Lightweight (but does not blow away)
  • Solve drainage issues

Disadvantages

The use of pumice only comes with a few disadvantages, but they aren’t as troublesome as some might think.

  • More expensive than perlite
  • Not available always

Benefits of Using Perlite and Pumice

  • Both pumice and perlite increase soil aeration and decrease the risk of waterlogging.
  • These materials are ideal for growing succulents and cactus plants, as well as establishing projects such as fairy gardens. You can use them in any type of soil mix.
  • These additives do not retain water. That’s why they can be used with other materials like coco coir and peat moss to balance water retention and drainage.

Due to their common benefits, it is quite hard to determine which one is the best one to use. 

In this next section, we compare the major differences between perlite and pumice.

Perlite vs. Pumice Comparison

perlite-vs.-pumice-comparison
  1. Because pumice is heavier, it does not blow away in storms or winds, unlike perlite, which is lighter. You may use pumice to increase the weight of potted plants that may trip over during a storm.
  2. Pumice is more expensive than perlite.
  3. Perlite can be found in the local garden center, but pumice is not widely available.
  4. Pumice is larger in size and has a white to dark gray color. Perlite can be of various sizes and the colors can range from dark gray to black.

This perlite vs. pumice comparison may give you an idea of the overall characteristics of these two growing mediums.

Which Is the Better Growing Media to Use?

These two garden soil amendments are great for growing any succulent and enhancing garden soil drainage. 

Both perlite and pumice can be used in the soil to improve oxygen levels. 

Pumice can be used on sandy soils as it can increase the water-holding capacity of the soil. 

Further, pumice can also be used in clay soils, which are notoriously known for having poor-draining soil.

Pumice particles are heavier, so you can use them in windy areas. In addition to their practical features, you can also use them as decorative stones.

Finally, the processing of pumice is environmentally friendlier than perlite.

In contrast, perlite can be used in light mixes or potting soils. Also, you can use it in the garden.

However, it would be best to take precautions as the perlite dust can be dangerous to your respiratory system.

With the pros and cons analyzed, we would recommend using pumice over perlite.

FAQ

Is pumice better than perlite?

It is preferable to use pumice for plants when the plant is tall, since the weight of the pumice may help prevent the pot from tumbling over. Additionally, pumice lasts far longer than perlite. Pumice, in contrast, may be more difficult to come by at the shop, particularly in the crushed form that is usually used in gardening, and more importantly, it may be more expensive than perlite.

Can I substitute pumice for perlite for growing plants?

Yes, you can substitute pumice for perlite. There are several benefits to growing plants in pumice. It decreases water runoff and fertilization by enhancing soil absorption in sandy soils, which minimizes runoff and fertilization. It also absorbs excess moisture, which helps to keep the roots from rotting. Pumice does not degrade or compress over time in the same way that other soil supplements do, which means it contributes to the preservation of soil structure.

What can be substituted for perlite?

Alternatives to perlite may vary depending on the use and the qualities of the material. For example, aeration alternatives to perlite include calcined clay and coarse sand. Sand and clay are cheaper and provide better drainage than perlite. Further, depending on the purpose in your garden needs, you can use bark, coco coir, peat moss, rice husks, vermiculite, calcined clay, and granite gravel as alternative materials to perlite.

Conclusion

Both pumice and perlite can be used to improve the soil drainage system of the garden.

You can grow plants like the snake plant, aloe vera, jade plant, and other cactus species.

Pumice and perlite can effectively solve any drainage issues in your garden soil.

These soil amendments may not increase the water holding capacity of the soil like other materials, such as coco peat, vermiculite, or peat moss.

Still, they can solve many problems in your garden. 

References