Perlite vs. pumice: Which is best for your plants?

Whether you’re a plant lover with a green thumb or someone who’s new to gardening, you probably know how important soil quality is for plant growth and health. However, apart from choosing different types of soil, you'll soon discover that there are even more options when it comes to additives. This is where things can get a bit confusing.

In this guide, we’ll compare pumice vs perlite and help you determine which is best for your plants. Learn the differences between two of the most common soil additives and how each can make a difference in your gardening experience.

What is perlite used for?

Perlite, technically, is a type of volcanic glass with high water content. It is processed and expanded through heating to produce a lightweight, white material used for aeration and improving soil drainage. It’s a staple in potting and composting mixes and is renowned for its ability to assist root growth and moisture retention.

What is pumice used for?

Pumice, on the other hand, is another volcanic byproduct characterized by a rough, porous texture. It has been used historically in horticulture to condition the soil because it offers superior aeration, drainage, and nutrient storage.

Perlite vs. pumice: Know the differences

When considering perlite vs. pumice for plants and garden maintenance, it’s crucial to understand the key properties that set them apart. These volcanic substances share some similarities in improving soil structure, but they also have unique differences that can significantly influence plant health and growth. 

Whether you’re a beginner gardener or an enthusiast, this guide will walk you through the distinct characteristics of perlite and pumice to help you make an informed decision. 

In terms of texture and weight

Perlite is often described as soft with a sponge-like texture. This makes it perfect for seed-starting mixes and plant propagation, as it helps retain moisture and is gentle on delicate roots. 

In contrast, pumice has a coarser, more abrasive texture because of its larger pores. This makes it ideal for improving drainage in denser soils.

When considering weight, perlite is noticeably light and airy, which allows it to float on water. Meanwhile, pumice is heavier and denser. This provides stability within a soil mix.

Aside from the obvious implications of texture and weight, these factors also affect how easy it is to clean your garden. Perlite is often easier to handle and is easier to mix into the soil or remove if needed.

In terms of nutrients

While neither perlite nor pumice add nutrients to the soil, pumice can hold onto nutrients more because of its pores. This can, in turn, be accessed by plant roots. For perennial plants, it may be a better choice as it can provide long-term nutrient availability. 

Perlite also retains a small amount of nutrients due to its porosity. However, its lightweight nature makes it susceptible to nutrient leaching and will possibly require frequent fertilizer applications.

In terms of water retention

In terms of pumice vs. perlite water retention, the latter mainly holds water on its surface. This aids in soil moisture without making it soggy, so it’s typically preferred when growing herbs, and root rot can be a problem. Even better, when mixed with clay soils that are already absorbent, perlite provides much-needed texture.

Pumice, however, can absorb water within its porous structure. This means it can steadily release all the water it contains for plant use and is more suitable for succulents and dry-loving plants.

In terms of aeration and drainage

Both additives promote excellent aeration and drainage, but due to perlite’s light density, it can become compacted over time. This makes it less beneficial in the long run.

Pumice retains its structure better, so it still has air and water spaces even after prolonged use. This makes it a better option for long-term garden soil amendments and can even aid in routine maintenance and garden tidy-ups.

In terms of versatility

Pumice can be more versatile and reused multiple times because of its durability. It also has the ability to slightly adjust pH levels, depending on its limestone content. 

On the other hand, perlite tends to break down over time and may need to be replaced in soil or potting mixes. However, its lightness and low cost make it a popular choice for hydroponic systems where plants are not grown in soil.

When it comes to pumice vs perlite for indoor plants, a combination of both is recommended, as each has its own unique benefits and level of flexibility. In terms of landscape gardening, though, pumice is more suited for outdoor applications. 

In terms of cost

On average, perlite is generally more affordable and accessible than pumice. This is because perlite is more widely produced and used in various industries, such as construction and horticulture. 8-quart bags can run from $5 to $17. There are also larger portions in 4-cubic-ft-bags that can cost $20 to $40. For this reason, perlite is often the go-to choice for local garden planters.

Depending on your location, pumice may carry a higher price tag and can be harder to source in gardening centers. For instance, similar 8-quart bags can cost between $20 and $45, depending on grade and coarseness. Meanwhile, 4-cubic-ft-bags can cost anywhere from $50 to $70. 

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