Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden.
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LECA, or Lightweight Expanded Clay Aggregate, are small baked clay balls containing thousands of macropores, making them popular for various applications.
In horticulture, LECA balls are used as a drainage additive to traditional potting soil, for root anchorage in hydroponic gardening, and as a stand-alone growing medium. LECA clay balls are stable in water, and LECA’s porous material helps trap air and nutrients for plant roots.
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Other Lightweight Expanded Clay Aggregate Uses
Other than growing plants in LECA, LECA pebbles are also used in roadworks, water purification, and the building industry. This outstanding aggregate is its most recent application for growing plants.
LECA as a Water Purifier
You may be interested that LECA was first used for water purification and building materials. In search of a solution to make concrete lighter without losing strength,
As a water purifier, LECA is getting increased attention for its ability to absorb phosphorus and other chemicals. Its ability to host microorganisms makes it even better for plant growth. Microorganism hosting is improved by adding biocarbon.
LECA as a Substrate in Wetlands
LECA has been increasingly used as substrate material for constructed wetlands given their phosphate removal capacity, hydraulic conductivity, mechanical strength, and plant rooting and biofilm growth supporting structure.
Because of their high porosity and high surface area, LECA clay balls are a fantastic medium for biological purification. Raw water contaminated with ammonia, manganese, iron, etc., responds well to biofilm processes.
Drinking water treatment, wastewater treatment, and on-site treatment are just some of the many water and wastewater treatment applications for expanded clay pellets.
LECA in Construction
Lightweight aggregate is a type of coarse aggregate that is used in the production of lightweight concrete products such as concrete blocks, structural concrete, and pavement.
LECA has proven itself as an efficient and durable lightweight aggregate suitable for several civil engineering applications, including noise reduction, fire retardant, and insulation properties.
The Use of LECA for Plants
Hydroponic systems work best if an inert growing material is used for plant anchorage. This allows growers to accurately regulate the hydroponics fertilizer systems, control pH, and the aeration of the plant’s root systems.
LECA is becoming increasingly popular in hydroponic systems, both passive and active ebb and flow systems, because the little balls act as a sponge, soaking up water from the supply feed and making it available to the plants for extended periods.
Healthy Roots, Healthy Plants
But it’s not only hydroponic growers that are interested in healthy roots. Indoor growers are just as interested in a healthy root ball. Most plants, indoors and outdoors, grow best when their root system is healthy, i.e., they have access to oxygen.
Leca serves as a substitute for soil by giving the plant’s roots the same kind of support they would need to develop and remain stable. A plant’s root system will grow to get water, eventually passing through and around the LECA.
Roots in any hydroponic system absorb nutrient molecules from the water, and their xylem transports them throughout the plant. Leca is a semi-hydroponic growing medium. Hence a liquid fertilizer is required to maintain the plant healthy.
Indoor plant enthusiasts wanting a more hassle-free approach to plant care have made LECA a popular growing media choice. LECA’s inert composition and the porous nature of the clay balls mean that plants don’t need to be watered as regularly as they would in soil.
Growing houseplants, including those with robust roots found on aroid plants (philodendron, monstera, aglaonema; alocasia; anthurium, etc.), will flourish in LECA as a growing medium.
LECA for Planters
Worried about water drainage in your raised planters? Using soil throughout the planter is one way, but drainage can be challenging, even with drainage holes. Unlike soil, LECA doesn’t compact and boosts drainage.
A 4-inch layer of LECA at the bottom of your grower will ensure proper drainage. Grow plants as usual in potting soil, mixing some LECA into the potting mix. The same applies when you grow indoor plants.
LECA for Potted Plants
The biggest challenge to growing houseplants is lighting and overwatering. LECA allows you to water plants knowing that your plant root system won’t be compromised. Plant roots need oxygen, and house plants in LECA are ensured of aeration and proper drainage.
When done correctly, transferring plants from soil to LECA isn’t a difficult task, but it must be done carefully to avoid damaging the root system in the transfer. Choose healthy plants.
Younger plants are usually better for this transfer. After the Leca is prepared to accept a new plant, you can follow these steps to transfer it from its old pot:
- Gently remove the plant from the soil (best to do this when it is dry so it won’t stick to the roots) and rinse any organic matter. The soil can carry microbes that may lead to root rot. Be gentle with the roots to not break them, but abrasive enough to remove any dirt.
- Allow the roots to dry for up to an hour. This will dry up and loosen any bits of dirt that might have remained on the plant, and it will dehydrate the roots just enough that the thirsty plants will eagerly absorb water once planted in the Leca.
- Ensure the container buffer is maintained to keep the roots out of the water and prevent root rot. Submerged roots in transition will be weaker and more susceptible than usual until they get used to their new situation.
- Be sure to use a hydroponics fertilizer that supports root growth for this transitional period, helping the plant avoid transfer shock.
Plant roots that grow in soil have fewer root hairs than those that grow in water, and they will need to expand and adjust to the new space and nutrient delivery method.
How Expanded Clay Balls Are Made
The production of lightweight aggregate begins with mining or quarrying the raw material. The material is crushed with tapered cone crushers and screened for size.
The material that passes through the screens is fed to a rotary kiln running at 2200 °F (1200 °C). As the material is heated, it liquefies, and the kiln’s rotary action rolls the product into little LECA balls. The carbonaceous compounds in the material form gas bubbles, expanding the material to double its original size.
LECA Balls and Nutrition
Since LECA is inorganic, it does not supply nutrients like the soil. The only way for the plants to get the nutrients they need is if fertilizer is added to the water they are soaking in.
The macro and micronutrients that houseplants need to thrive will be in equal measure in a liquid nutrient solution. Fertilizers have the correct nutrients isolated and ready for use in the water when typically, these would be broken down and made available by the microbiome in the soil.
LECA Balls For Plants
Growing plants in Leca has gained popularity because of its several strengths as a growing medium. It isn’t necessarily better than soil, but it’s a different option if you could benefit from any of its characteristics or if you like the look.
Leca makes watering easier through the clay pebbles’ wicking process, which distributes water to the plant’s roots.
Overwatering is one of the most common indoor plant problems, and when done right, a Leca watering system will keep your indoor plants sufficiently hydrated.
The water will deplete only as quickly or as slowly as the plant absorbs it. For this reason, you can water the plants less frequently when using Leca.
Fungus, microbes, spider mites, and fungus gnats live in wet soil. When you use Leca balls, there’s little chance these could survive on the inorganic material with nothing to feed on.
Reusing Leca is easy since it doesn’t decompose or deplete over time.
The clay balls provide an open-air structure that allows the root system to get lots of oxygen while remaining hydrated. A lack of oxygen is a primary cause of root rot, frequently due to water-saturated soils from poor drainage or overwatering.
Leca requires less maintenance than organic matter. It’s less messy than soil, and as mentioned, your indoor plants require less frequent watering when using clay pebbles.
Because of the way the clay pebbles and roots are arranged in the pot, you always will fill it to a specific level, taking the guesswork out of how much water the plant needs.
Prepare Your LECA For Use
How you arrange the LECA is very important to support healthy plant growth. You have to provide some space at the bottom of the container (about 1/3 of the pot) to keep the roots out of the water supply and avoid root rot. This buffer allows the water to sit, be absorbed by the clay pebbles, and irrigate the plant while keeping the roots dry and healthy.
LECA’s Role in Hydroponics
- Clean the Leca pebbles of their built-up clay dust, rinse them out and let them dry for a couple of days, at least 24 hours, before planting in the Leca.
- Test your water’s pH, add any needed balancer, and add liquid fertilizer. Moisten the clay pebbles with this fertilized water before adding the plant to the pot; this will jump-start the wicking process.
- Fill a net pot 1/3 of the way with the Leca growing medium.
- Put the plant in the upper 2/3 of the pot, and fill it with the Leca medium as you would with soil: hold it in place and surround it with the clay balls.
- Fill your outer pot with water up to the height of the bottom layer of Leca.
- Put the net pot into the outer pot.
The net pot makes lifting the Leca out for cleaning easier and allows you to see how much you’re watering into the outer pot. You can measure the amount of water needed the first time and how long it takes to deplete to guide you in your watering schedule mainly.
If you don’t want to use a net pot, follow the exact instructions and put the LECA and the plant directly in a water-tight pot in the same 1/3 and 2/3 layering method.
- use an organic hydroponics fertilizer
- add 1/3 of LECA balls, then gently place propagated plant on top
- fill in the rest of the space with leca balls soaked in fertilized water
LECA for Propagating Plants
Planting a cutting is a great way to get a plant started in Leca. This way, the new roots will grow adapted to the open-air system and hydroponics fertilizer. You’ll find the steps to propagating a plant destined for Leca are as simple as for any other propagation:
- Clip a stem from the desired plant with some leaves on it.
- Put the clipping into the prepared Leca pot with fertilized water.
- The plant will absorb moisture from the stones’ pores as in a soil or water propagation arrangement.
- As with a soil-to-Leca transfer, use a fertilizer that targets root health to avoid transfer shock during the transitional period and help the roots grow strong.
Cleaning and Reusing LECA
Expanded clay needs to be cleaned monthly. The cleaning process, known as flushing, is important because nutrients from the fertilizer will build up in the pores of the pellets and disrupt their ability to transfer and hold water.
The clay balls shouldn’t be allowed to dry out when a plant is in them since the root system will then be exposed to open air without any moisture.
Flushing the Leca and rinsing off the plant will also help keep buildup off the roots. When fertilizers dry out, any solids left over on the roots might damage them after a while.
Rinsing off roots when flushing the Leca is particularly good for plants transported from the soil since it may take a few rinsing sessions to clear the roots of all the organic matter from its former home.
In Closing
LECA is indeed an amazing product for keeping roots aerated and healthy. Whether used for root anchorage in hydroponics or as a base for improved drainage in potting soil, is worth the initial investment.
I will not think twice before suggesting that novice plant keepers start with Cebu Blue potted plants because they are so forgiving. They will soon be reaping the benefits of cultivating them and will have full plants with a spectacular display of blue-silver foliage.
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