Perlite Is the Secret to Improving Soil Drainage—Here's How to Use It in Your Garden

As any avid gardener knows, keeping plants happy and healthy is the number one goal for any type of plant care, be it container gardening, houseplant care, or gardening in beds. One useful material to add to your gardening routine is perlite, a substance that can be mixed into the soil and can aid in everything from proper drainage to healthy root development. Ahead, we spoke with two gardening experts to explain what perlite is, how it works, and how you can use it in your own gardens.

What Is Perlite?

Perlite is a volcanic glass that is often used in gardening due to its lightweight, porous nature that aids in healthy plant development. "It is made from a type of volcanic glass called obsidian," says Susan Brandt, co-founder of Blooming Secrets. "When obsidian is heated to high temperatures, it expands and forms small, white granules with numerous tiny air pockets."

Gardeners often add perlite to their gardens because those air pockets help with drainage and aeration, leading to improved soil structure, better root development, and less chance of waterlogged conditions that can lead to root rot, says Brandt. You can purchase perlite at gardening centers, nurseries, home improvement stores like Lowes or Home Depot, or online on Amazon.

Types of Perlite

There are a few different kinds of perlite to choose from depending on your gardening needs. These range from coarse to very fine perlite, as well as some specialized types.

Coarse Perlite

Composed of larger particles, coarse perlite is good for preventing waterlogged conditions in both potted plants and garden beds. "Coarser perlite, with its larger particles, is better for improving aeration in potting mixes and is commonly used for plants that require well-draining soil, such as succulents," says Tony O'Neill, a gardening expert, author, and educator.

Fine Perlite

Fine perlite has much smaller particles and "is often mixed with potting soil or other growing media to enhance moisture retention," says Brandt. "It provides a lightweight structure allowing roots to access air and nutrients easily," O'Neill adds that it is often used for seed starting as it's gentle on delicate roots.

Horticultural Perlite

When at your gardening center, you might see perlite labeled as horticultural perlite—this type of perlite has been processed specifically for home gardening purposes, says Brandt. "It undergoes heating at high temperatures, causing it to expand and become lightweight," she says. "This type of perlite is ideal for seed starting, propagation, and root cuttings."

Agricultural Perlite

As a home gardener, you likely won't require agricultural perlite, which is formulated for large-scale farming operations. Agricultural perlite is used "as a soil amendment to improve drainage and increase water-holding capacity," says Brandt. "It can be blended with various substrates for hydroponic systems or mixed into soil for better plant growth."

Benefits of Using Perlite

Adding perlite to your garden's soil can keep your plants happy in several ways. Besides improving soil drainage and aeration, "it helps to prevent soil compaction, allowing roots to grow freely and access oxygen more efficiently," says O'Neill. "Additionally, perlite can hold water at its surface, which provides moisture to plant roots while also ensuring the soil doesn't become waterlogged."

Aids in Root Development

Because of perlite's ability to help with soil aeration, plant roots have some more space to spread out. "Its structure encourages root growth and development by providing a loose, well-draining environment that allows roots to expand freely," says Brandt.

It's pH Neutral

You won't have to worry about upsetting your soil's natural pH if you add perlite to the mix—it's considered pH-neutral and can be used for a variety of plants that have different soil acidity requirements.

Helps Prevent Diseases

Disease prevention is always top of mind for gardeners, and using perlite can actually help with that. "Due to its non-organic nature, perlite does not provide a favorable environment for pests or diseases to thrive," says Brandt. "Using perlite in your garden can help reduce the risk of plant diseases caused by pathogens present in organic matter."

Works for Years

When you add perlite to your garden's soil, rest assured that it will provide its benefits for a very long time—it doesn't break down very easily. "One of the main advantages of perlite is its durability; it doesn't degrade over time, meaning it can help maintain soil structure for years," says O'Neill.

Disadvantages of Using Perlite

While there are several advantages to using perlite, there are a couple of disadvantages to be aware of as well. For instance, because of its drainage capabilities, perlite can't hold onto nutrients in the soil well. "Regular fertilization is necessary to ensure plants receive adequate nutrition," says Brandt.

Perlite can be kind of dusty, so you'll want to make sure you're wearing a mask when adding it to soil. Additionally, perlite is made from a non-renewable resource, so you want to keep environmental sustainability in mind, says O'Neill.

How You Can Use Perlite In Your Garden

You've purchased a bag of perlite—now what? Here are some of the most useful applications of perlite for your home gardening routines.

• Seed starting: If you're keen to start seeds indoors, adding perlite can really help. "Its lightweight nature provides optimal conditions for germination by allowing air circulation around the seeds," says Brandt.
• Container gardening: Plants grown in containers need more help with soil drainage than those in garden beds. "Adding perlite to your potting mix ensures excess water can easily drain away, preventing waterlogged roots and promoting healthy plant growth," Brandt says.
• Root propagation: "Perlite is a wonderful tool for propagating plants from cuttings or dividing rootbound plants," Brandt says.
  
• Top dressing: Sprinkle some perlite on top of your potted plants' soil—it'll act as a protective barrier and keep the soil moist for longer.