What Are Perlite & Vermiculite? How & When to Use Them?

Perlite & Vermiculite are inorganic soil additives known in horticulture very well. To make these two materials, manufacturers expand mineral materials mined from nature.

However, the two materials are different from one another. Vermiculite is soft and has a brown color slightly shiny. On the other hand, Perlite is porous and white and has sharp edges.

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The two are known for helping to aerate and lighting the soil mixes. Perlite and Vermiculite have a tremendous value in container plant culture, and helps in seed starting and rooting.

So, what are perlite & vermiculite? What is the difference between the two? And, what are used for?

What is Vermiculite?

A Material mined from Rocks!
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The first material is Vermiculite that can be mined from rocks. It is a group of minerals like iron, magnesium, and aluminum.

The same as Perlite, This material is also heated to a very high temperature of 1652 degrees Fahrenheit. Vermiculite contains small drops of water in it. When heated, it turns into accordion-shaped, worm-like structures instead of popping.

The structures are composed of numerous layers of thin plates. The particles are from eight to twenty times bigger. 

The chemical composition makes Vermiculite lightweight, odourless and water absorbent. Vermiculite colors range from black to shades of brown and yellow, and sometimes even gold and coppery.

What is Perlite?

A Material found only in Volcanoes!

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To put it simply, Perlite is a glass extracted from volcanoes and then saturated with water.

The process of making Perlite requires heating this material to 1600 degrees Fahrenheit, which makes it pop like corn kernels, and then turn it into popcorn.

This process of expansion makes the original material thirteen times larger. The final product is a very lightweight material.

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Finished perlite weighs only six to seven pounds per cubic foot. Perlite expands because of the water that explodes and evaporates, which creates tiny air pockets.

The air pockets are able to hold water on the outside. As a result, it allows plants to get the water easier, which couldn’t happen if the air pockets hold the water on the inside. Perlite has a tendency to dry out rapidly, and it is reusable.

The perlite has a white color, which makes it difficult to distinguish it from Styrofoam.

Vermiculite Vs Perlite.

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Perlite and Vermiculite have some differences.

  • Perlite contains an amount of alkaline between 7.0 and 7.5 pH, which makes it a bit dangerous of used too much. Even though It has a great capacity to keep the soil mix from compacting, Perlite should be used moderately, or it will cause some minor nutrient issues.
  • Most plants require more acidic conditions. The pH of Vermiculite that varies between 6.5 and 7.2, makes it safe and better for almost all the plants, and the impact on the plants is neutral.
  • Mixing Perlite with clay soils will eradicate surface crusting and wet spots. Perlite will keep soil temperatures due to its insulation properties. Horticultural perlite is available in different grades that depend on the way you want to use it.
  • Plant experts and professionals prefer Vermiculite for the rooting of cuttings. It also can keep moisture and plant foods, then releasing them to the cuttings as needed.
  • Vermiculite does not deteriorate, which makes it permanent. It is also Non-toxic, odorless, clean, sterile and does not get mouldy or rot.

What are they made for?

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In Horticulture, Perlite and Vermiculite are both good to use in the garden in order to prevent soil compaction, retain moisture and improve aeration.

Propagation of new plants and seed cultivation, also indoor container growing and composting require using Perlite and Vermiculite. However, there is a difference in usage. The usage of Perlite or Vermiculite depends on the plant.

Each of the two materials has a way to retain water, and how much water it can retain, which makes them suitable for different types of plants. Perlite is known for drying out rapidly for plants that need so much water.

Vermiculite is suitable for water-loving plants like some types of irises and forget me nots. For plants like cacti or rhododendrons that require well-drained soil, Vermiculite is not ideal, because it does not contain the right amount of water needed. Vermiculite, in this case, would retain moisture, which leads the plant to death or leads to root rots.

Using Perlite & Vermiculite.

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Perlite Tips :

  • If you want to use it for seed starting, mix perlite half and a half with Peaceful Valley soilless mix, coco peat or Quickroot.
  • In case for cuttings, use the same blend as before
  • For garden beds, apply a 2” layer besides compost and other soil amendments. Everything should be used at the same time, and make sure to work the perlite into the top 6-12” of soil. One application is enough to keep the soil loose and light for many years.
  • When it comes to container gardens and potted plants, You can use ⅓ perlite per container. Orchids and succulents like the perlite. Their potting soil could be mixed with half or more perlite if the plant needs more.
  • Perlite is ideal for storing bulbs over-winter, it will keep them fresh until you plant them in spring. To do this, alternate layers of perlite and bulbs, then cover with more perlite and store them in dark, cool, dry place.

Vermiculite Tips :

  • Vermiculite is great to help plants grow, it makes them absorb calcium, magnesium, potassium and ammonium needed to grow rapidly.
  • Using vermiculite alone or mixed with soil for seed germination will make the seeds to germinate fast.
  • For root cuttings, medium-grade vermiculite could be used directly. Just insert the cutting up to the node while watering thoroughly.
  • It’s possible to use vermiculite when arranging flowers. Put the vermiculite in the container, and saturate with water. Get rid of the excess and arrange your flowers, which saves the time of changing the water, spills and keeps blooms fresh all day.
  • Use vermiculite alone or with peat or compost for conditioning and lightening the soil. It will accelerate growth dramatically.
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