Clay pebbles, more than just an ornament mulch

Clay pebbles, or leca, are brown balls of clay that are of great use to plants.

It has the advantage of reliably managing water for plants, and it lasts a long time.

Thanks to its 100% mineral content, clay balls are useful for drainage, repotting and also decoration!

→ Other names for this include clay balls, hydroton… LECA is an abbreviation of Lightweight Expanded Clay Aggregate.

Uses of clay pebbles

Clay pebbles can be used in many manners, both ornamental and to enhance the living conditions of your potted plants.

• Drainage – All you need to do is pour a layer about an inch or two thick (3 to 4 centimeters) at the bottom of the container (pot, garden box, other) and this will increase air circulation, protect the roots and thus favor plant growth. Succulents, cactus and air plants can use nearly 100% clay pebbles as a growing medium.
• Repotting – To spur the growth of roots, it can be a good idea to mix clay pebbles into your special repotting soil mix to about 10% of the total volume. Especially useful for orchid soil mix, bonsai repotting, terrariums and kokedama projects.
• Decoration – For all your indoor plants, but also for outdoor garden boxes and pots, clay pebble is extremely ornamental. A surface layer about 1 to 1½ inches (3 to 4 cm) thick mulch will highlight the color of the plants.
• Hydroponics – These can be used as a substrate for growing lettuce, herbs, and other plants with hydroponics.

Humidity for houseplants

On top of being truly beautiful to look at, clay pebbles excel at keep the air around the plant moist. Many houseplants come from the tropics, where air humidity is naturally high.

Clay pebbles can raise moisture levels from 40-50% relative humidity to a more comfortable 80 % moisture, see how here. Wet the clay beads with rainwater to keep the pores from stopping up due to excess minerals in tapwater.

This will protect many houseplants from getting brown leaf tips!

Moisture retention for dry soil in hot weather

Water retention is important for plants to survive when the weather is hot. Adding clay pebbles in the soil is a great way to regulate soil moisture.

• Water seeps into the brown balls in the soil and accumulates inside its pores.
• When the soil is dry, water is released to nearby plant roots.
• This is like having lots of miniature oyas (ollas) in the potting soil!

Together with hydrogel crystals, clay pebbles are a boon to help plants survive drought, or help young trees start off in their first few years!

Just as for repotting, mix in about 10% volume to the soil mix used for planting your tree.

Fertilizer boost

Clay pebbles, per se, don’t really fertilize plants. But if you dunk them in a solution of home-made weed tea, they’ll pack a punch for weeks afterwards!

• Prepare your weed tea (nettle, horsetail, and more)
• Dip your dry clay pebbles in the solution directly, no need to dilute it. Let them soak for half an hour at least.

Once ready, spread them as mulch or add them to your pots and growing beds. In cases where the fertilizer mix smells somewhat, bury the leca balls into the potting soil for houseplants.

How is LECA made?

Leca is expanded clay – this means tiny air bubbles form inside.

It’s produced by flash-heating up to 2000°F (1200°C), regular, slightly wet clay balls in a super-hot oven. Water evaporates instantly, forming tiny bubbles of vapor. Vapor and other gases inside expand to look like a sponge or honeycomb. These connect to let the pressure escape.

→ This happens naturally in volcanoes during eruptions. It explains why pumice and, to a point, pozzolan, is so light it can float!

In the end, the structure is like a sponge, with lots of tiny cavities to retain water, nutrients, and clay.

Clay balls also go by other names: aggregates, brown balls or clay pellets and beads, just to cite a few.