Why do Clay Pebbles (LECA) Turn White?


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LECA is a very popular material when growing plants in a soilless medium. It is readily used in Hydroponics, Aquaponics, indoor farming and propagation of plants.

LECA turns white because of the nutrients and minerals within the water which gathers and evaporates from its surface. The evaporation of water from the surface leaves behind mineral salts which gives it a white appearance.

Using, Leca is an increasing trend when it comes to propagating and growing plants. Using leca or hydroton for growing plants produces good benefits when applied correctly. 

We are going to go through these benefits as well as the causes of the white coating we often find on its surface and what we can do about it, further in this article.

Leca turning white

What is LECA

The term LECA, also known as Hydroton, is the short form of ‘Light Expanded Clay Aggregate’. It is a lightweight, spherical shaped ceramic aggregate ranging between 8mm and 15mm.

The lightweight and other favorable conditions of the Leca make it best for hydroponics. Aquaponic farmers mostly use clay pebbles and it’s also a growing trend among houseplant owners as well.

How Leca is made?

Hydroton or Leca is prepared by heating clay balls to a high temperature of (over 1200 C) in a rotary kiln which gives it a round ball-like shape.

The heating also expands the volume of clay by 4 to 5 times its original size as a result of the water within the clay turning into a vapor.

This creates pores within the clay structure which gives it some of its useful properties.

One such property is its ability to hold water within its pores which is then made available for plant roots.

The properties of the material are as follows –

  • Ability to hold water
  • Lightweight 
  • Rigid
  • Fireproof
  • Thermally insulated
  • Anti-shrinkage 
  • Porous (when used together)
half barrel aquaponics
Leca Used In Aquaponics

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What is Leca used for?

Leca is used both in Aquaponics and Hydroponics. In both cases the leca, hydroton or clay balls are submerged in a nutrient rich solution of water in which the plant is grown.

The purpose of the leca is to provide support for the roots while holding the nutrients for the roots to absorb.

Nutrients can be added to the leca and by extension, the plants, via these methods –

Method Explanation
DripThis is where the nutrients are allowed to drip directly onto the roots of the plant in the leca
Flood and drainIn this method a bell siphon is used to allow the water to full up to the plant stem and then drain the plant container empty. The flood and drain cycle occurs in regular intervals.
FloodedThe nutrient solution is applied as a constant flo which covers the roots of the plant within the leca.

Leca can also be used to grow and propagate plants sitting in a container with a level of nutrient rich water. 

This is a growing trend among plant owners and provides a soilless method of growing plants which also eliminates all the problems that come from growing plants in potted soil.

Hydroponics using leca
Leca or Hydroton in NFT Hydroponics

Why is Leca useful for plants? 

Leca can provide a number of useful benefits for plants Which includes its water retention ability within its pores and its drainage and aeration abilities which it provides roots from the spaces between the leca balls.

Some of the benefits are as follows –

  • Provides an easy way for plant roots to grow and support the plant.
  • It greatly increases the aeration for plant roots
  • It helps you to easily water your plant and fulfill its water requirements.
  • It reduces the chances of infection with pests.
  • The checking of the plant becomes super easy.

What Causes the White Buildup on Leca

Salt residues are the major cause of the white buildup in the ebb and flow hydroponic systems.

The growing medium for the food cycle contains many dissolved salts and water, which the roots of the plant absorb readily.

There are a few more factors that lead to the deposition of white material on your Leca. 

The extremely high level of water

The deposition of salt residue may also result due to the evaporation of water.

During the food cycle, if the water level gets above the height of growing media, eventually, it evaporates from the top and leaves the white residue.

The nutrient ions are generally too heavy to evaporate, so they come together and accumulate on your hydroton. So maintain the water level and never allow it to surpass the height of the media. 

The growing media of your Leca plant is getting old. 

Natural Hydroton contains pores that are good for the right distribution of water and oxygen to the plants’ roots.

Over time, the leftover salts clog the pores. No matter how much water you use, the pores don’t reopen.

If you have been using the same hydroton growing media for a long time and notice salt deposits forming on it.

Then it’s likely that your Leca will turn white.

Fortunately, there is a way to rejuvenate the leca for reuse, and that’s with heat (boiling the water)

Can I Reuse Leca? 

Yes, of course, you can reuse your Leca. Fortunately, Leca is reusable for an indefinite period. Also, you are in luck to use the Leca of one plant for another one.

If you thoroughly rinse off leca and remove the salt buildup of organic matter from it, you can reuse it several times. 

However, when it comes to soil, it may not be reusable. The previous plant will already consume the essential nutrients required for the plant, and little would be left behind for the new one. 

If you have mixed leca in the soil, you will have to remove the old soil and thoroughly clean the leca by soaking it in water to dissolve the old nutrients, soil and roots.

The leca should then be allowed to drain free and dry before reusing in a new planter.

Clay pebbles

How to Remove the White Stuff from Leca (Step by Step Instructions) 

Do you get the white residue on your Leca from time to time? Looking for the method to fix it out? Here is the step by step instructions that you must follow to remove the white stuff from leca / hydroton. 

  1. Pull out used pebbles. 

    You must be careful during the process of removal of the used pebbles from the active plants.

    If the pebbles get stuck into the plant roots, let them stay there and don’t tug them off because it may harm the plant’s roots.

    When they are seized within the roots, it means they have been used. So be gentle in the removal process. 

    Once you take off all the pebbles, put them into the large cooking pot. Make sure that all the pebbles fit in easily. 
  1. Pour over the hot water into the pebbles. 

    Put the pot near the sink and pour as much hot water into the pebbles as they submerge fully.

    Afterward, shake the pot forcefully so that all the pebbles shift their position. Continuously fill in the water until all the pebbles are drowned in the water. 
  1. Mix the pebbles with your hands

    Now use your hands and thoroughly mix the pebbles all over the water.

    The movement of pebbles in the water will remove all the debris and cleanse out the pores. 

    Note: if the pebbles get grimy during the mixing process, don’t get afraid. Continuously rub their sides to loosen the debris. 
  1. Remove the water and repeat. 

    Now empty the dirty water into the strainer near the sink. This is the best way to know how much debris has been removed from the pebbles.

    Take up some of the pebbles in your hands and feel them. Sometimes the pebbles and gunk have the same color, so it might be difficult to note the difference. 

    Now look at the strainer and notice how much debris has been removed. It’s not done! Now you have to rinse off the cooking pot and again fill it up with the hot water.

    Again mix the pebbles with hands and repeat the process of straining.

Tip: if the pebbles are extremely dirty, you can repeat the above process several times.

  1. Put Clay Pebbles in boiling water.

    Once you have completed the rinsing of dirty pebbles, now boil them at in a pot. The boiling won’t destroy the durable clay balls.

    Rinsing and straining will loosen up the dirt stuck to the pebbles. While boiling will completely remove the loosened debris from them.

    It is probably the best method to sterilize them and eliminate harmful microbes.

    During the entire cleaning process, you will see the murky red substance around the pot’s top.

    What’s that? It is a mixture of all the remnants and dirty substances coming out of pebbles. So boiling is the most powerful step, as it extracts out the leftover material.

    So don’t forget to boil Hydroton for at least 10 minutes.
  1. It’s time to dry them. 

    Now let the excess water and remaining materials drain out of the clay pebbles.

    The porous pebbles hold a significant amount of moisture, so you must allow them to stand for 24 hours.

    Every once in a while, you can shake them off and turn around for the proper drainage.

    Are your hydroton pebbles fully dry? Now just put them back into the plant.   
leca with white residue
White residue on Leca

Can the White Build up Harm Plants?

The white buildup on the plant can adversely affect them. It may cause the

  • Browning of leaf tips
  • Burning of plant 
  • Retard the normal growth process
  • Damage root tips
  • Abort lower leaves
  • Wilting

The white buildup occurs due to the accumulation of highly soluble salts with a high pH level, which has been left behind from evaporation.

The rise in the pH hinders the availability of essential nutrients and sometimes mutates the structure of important nutrients.

Such alteration renders the useful nutrients into useless forms, which results in the nutrient lockout.

In such a situation, the deficiency of essential nutrients occurs, and visual signs of nutrient unavailability appears.

If you are considering the use of fertilizers to deal with this problem, then stop right away because the addition of fertilizers will only aggravate the situation and result in severe plant injury.

Pro tip: 

find out the fertilizer that doesn’t contain the salts in it.

Firstly eradicate the salt buildup before adding the fertilizer. 

Why is it Useful to Use Leca in Hydroponics and Indoor plants?

  1. Leca is porous, so it can absorb the excess water. 
  2. Houseplant pests usually live with the rooting mater. But leca doesn’t have any living organism which keeps the growth of pests. 
  3. The same leca can be used for various houseplants, so it’s ideal for small spaces. 
  4. Leca is cheap and dust-free.

Can I Mix Leca/ Clay Pabbles with Soil?

Leca can be mixed with soil just like other soil amendments because it will help the soil with drainage and aeration. The mixture should be kept such that the ratio of soil is higher than the leca.

Therefore a mixture of around 75% soil to 25% leca is recommended for providing soil with the nutrients from the soil with the added benefit of drainage from the leca.

Reasons why leca can be added to the soil

  • It’s is pH neutralIt doesn’t affect the pH of the soil
  • Good Drainage ability Increases drainage while still holding some moisture for the plants
  • Helps with soil aerationHelps provide oxygen to the plant’s roots
  • It is Sterile It can be used for a long time without leaching any chemicals into the soil.

Pro Tip:

when you buy a fresh batch of leca it is advised that it be soaked in water and washed thoroughly. This removes any loose dust particles from the leca and cleans any residual build up that it may have.

Dust from Clay pebbles
Dust emanating when new Leca is pored

How often do you Water a Plant in Leca?

A plant grown in leca does not have to be watered. Instead, the plant is placed in the leca is partially submerged in a small amount of nutrient rich water which moves upwards via capillary movement or a wicking action.

This nutrient rich water is also called hydroponic solution.

The roots of the plant are stimulated by the moisture and nutrients from the leca causing it to grow downwards into the water.

Water is only added when the nutrient water level is low and needs topping up. 

Additionally, after some time the water in the container with the plant should be replaced as the nutrients are depleted. 

In this case, the time it takes to replace the nutrient rich water will be dependent on the plant that is being grown and the amount of nutrient water that was initially placed in the container.

Conclusion

To ensure the hydroton continues to provide essential support to your houseplants, you need to spare some time to clean the salt buildup.

Pellets are highly porous, so they absorb a lot of salt which limits their life.

The rinsing and cleaning will increase the life of leca and make it more effective for your plant. 

What is your opinion about Leca? Which plant grows well with them? Share your ideas with us in the comment section below. We would love to hear from you. 

JayLea

JayLea has a passion for plants and has been gardening since 2015. He has valuable knowledge about gardening and houseplant care and can answer everyday practical questions that every plant owner has.

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