Lava Rocks: Why and How to Use Them

If you’re a regular peruser of the houseplant sides of Instagram and TikTok there is a good chance you’ve stumbled upon posts about, or atleast containing, these rather unassuming little clay pebbles. Referred to by a couple of names like LECA (lightweight expanded clay aggregate) and Lava Rocks, these organic clay pebbles have gradually grown in popularity as more and more of us delve deeper into the nuances of indoor plant care.

What are Lava Rocks?

Made from volcanic rock, Lava Rocks are small pebbles formed by heating clay to roughly 1200 degrees Celsius. When heated, the gasses within the clay expand forming small air pockets and channels that can store water. It can be used as a method of increasing humidity around your plants, a propagation medium and semi-hydroponic growing medium for indoor plants. The porous nature of the organic rock gives it an innate capacity to absorb and gradually release water either to the neighbouring roots of a plant or into the surrounding atmosphere. It is thanks to this quality that it has risen in popularity, particularly among more keen botanists.

How Can I Use Lava Rocks?

A Passive Plant Humidifier

Providing your tropical houseplants with adequate humidity can sometimes be a challenge, particularly during colder months when the air in our homes becomes that bit drier because of our central heating systems. While misting is an option, using lava rocks may offer a less taxing and more consistent solution.

By placing a layer of lava rocks either in the pot saucer or a tray underneath your plant’s pot and soaking them with water, the lava rocks will gradually allow the water stored within them to evaporate into the surrounding air. This will steadily increase the humidity levels in the air around your plant. When your lava rocks look dry pour some additional water over them to soak them again.

When it comes to how regularly you should re-soak your lava rocks you must consider how warm your plant's space is. Fortunately, it is visually easy to see when your lava rocks have dried out; they will appear lighter in colour and more dusty in texture. There is also little risk of making your lava rocks 'too wet' per se. Provided you keep the water level in the saucer below the top of the lava rocks you won't risk passively overwatering the plant above.

"The lava rocks will gradually allow the water stored within them to evaporate into the surrounding air."

Propagation Potential

Lava rocks can be used as an excellent alternative to propagating plant cuttings in water directly. By placing your cuttings in a glass or jar of soaked lava rocks the developing roots are much less likely to succumb to issues such as root rot as the rocks gradually supply the new roots with water as it is needed. The natural aeration of this medium also means the new roots are far more likely to make a smooth transition into more traditional potting soil when the time comes. On top of this, the lava rocks can be washed and reused in future meaning they are a sustainable propagation medium also.

A Potting Soil Alternative

The most common application you will see online is people experimenting with Lava Rocks as a growing medium instead of traditional indoor plant potting soil. There are many benefits to doing so. As is the case when propagating plants, their ability to gradually release water as the plant needs it reduces the risk of root rot. The lack of organic material around the plant also gives soil-dwelling pests nowhere to live and multiply. Lava rocks are also easy to store, can be kept for long periods of time without the risk of drying out, and are reusable, as previously mentioned.

However, unlike potting soils they are not innately rich in nutrients that can support and promote healthy plant growth. As a result, when growing in lava rocks one must supplement the plant with a hydroponic plant food such as Botanopia’s Organic Plant Feed.

A variety of plants can grow in Lava Rocks thanks to its consistent and gradual water supply. Generally, plants that are happy to dry out entirely between waterings tend to be the best candidates. Popular plants such as Sansevierias, Monsteras, trailing and vining plants like Scindapsus Aureus and Philodendron Scandens all tend to do well in this Medium.

To transition your plant to Lava rocks follow these steps:

  1. Thoroughly Wash your Lava Rocks by running water through them to remove any dust and dirt.
  2. Soak them in a bowl of water for several minutes.
  3. Remove your plant from its current pot.
  4. Thoroughly clean the root system to remove any organic matter from around it. It is important that all potting soil is removed as if this is not done currently it can rot later when the plant is placed in the lava rocks.
  5. Fill your pot of choice with lava rocks and gently repot the plant in the medium.

Sansevieria Zeylanica - Snake Plant

Shop Now

Clay: The Contemporary Botany Company

We lovingly curate a selection of indoor plants & handmade pots. Delivered across Dublin and Nationwide.

Words by: Clay: The Contemporary Botany Company

Images by:

A Butchers Hook

Peperomias: A Beginner Collector's Perfect Plant
The Best Indoor Plants that are Safe Around your Pets
Trailing Indoor Plants that Everyone Should Own