What is leca?
The term leca stands for Lightweight Expanded Clay Aggregates. Leca are small round, brown balls available in different sizes for various applications. As a growing medium the typical size is between 4-10mm (0.15-0.4 inch). These light porous balls are commonly used in horticultural applications and water purification processes.
For plant use leca is a great way to alter soil chemistry to benefit plants or as its own growing medium. It works best for plant growth when used in aquaponics and hydroculture applications.
How is Leca made?
Leca is made from small clay pellets that are placed inside a 1,200 °C (2,190°F) rotating kiln. The extreme temperatures cause the clay pellets to expand 5 times in size and form thousands of pores. This is caused from the gases trapped inside escaping the clay pellets from the heating process. The rotating kiln gives the leca its smooth round shape, similar to making a ball in your palms.
Benefits of Leca
Leca Makes an excellent growing medium for a multitude of reasons. It makes a great growing medium for developing plants and full grown plants alike. The biggest benefits to leca are outlined below.
Ability to check on your plants
Unlike typical growing mediums like soil; One of the advantages of growing indoor plants in leca is the increased visibility of the plant’s root system. This allows you to better monitor your plants root health and help in the early detection and treatment of root diseases like fungal based root rot.
Easier to propagate plants
Propagating using leca is very similar to water propagating, with plants having constant access to water, however there are some benefits to using leca over water. Lecas ability to give plant roots constant access to water without requiring to be submerged makes it a great alternative. The leca acts as capillaries to transport water and nutrients to the roots (similar to water being absorbed up a sponge).
With water propagation indoor plant cuttings are more exposed to rotting with the lack of oxygen being the main culprit. Leca’s properties mitigates this risk with greater access to oxygen.
Leca is a great sustainable way to grow multiple plants over long periods of time. Leca can be reused indefinitely. It will require to be washed prior to reuse to ensure there is no transfer of potential pests/ diseases. Rinsing will also assist in removing any built up organic matter. Leca can be reused immediately or dried and stored for future applications.
High in oxygen
Due to the manufacturing process leca is extremely porous which aids in its ability to capture and hold oxygen. This is great for your plants roots and helps mitigate the risk of root diseases like root rot.
Leca also doesn’t decay or compact over time, which occurs in organic based soils from decomposition. This helps maintain a healthy air flow to the root system and provides ample oxygen to the plants root system.
Disadvantages of Using Leca
Although Leca is a great growing medium for indoor plants there are a few disadvantages to be taken into consideration. These mostly have to do with equipment and costs and have been outlined below.
Not suitable for all pots
Due to the nature of leca and it’s inability to hold nutrients (like organic based soils) the type of pot needs to be taken into consideration. Pots and vessels are required to have no drainage holes. This allows water and nutrients to be readily available for your plant, in turn promoting healthy plant growth. Decorative cover pots can be used with leca if desired as long as the inside pot has the ability to contain water.
Requires Additional Fertilizers
With leca containing no nutrients naturally, for your plants to thrive you will need to supplement the growing medium with additional liquid nutrients/ fertilizers. Alternatively similar to aquaponic systems, using water containing fish waste is a cheaper alternative to purchasing nutrients. However this is not specially formulated and results can vary drastically.
Costs of liquid fertilizers and/or nutrients will also need to be factored in. These upfront costs don’t factor in it’s ability to be reused which significantly reduces overall long term costs when used for multiple plants.
How to Use leca
When you first get your leca if not prewashed you will find that it is very dusty. This dust is typically just left over clay particulates from the manufacturing process. Although it is not technically harmful to your plants, it holds no nutrient value and makes for a bad look dirtying the water.
The best way to clean new leca is to put under running water for several minutes until the water begins to pass through clear. Next let them soak fully submerged in water from 2 – 12hrs (or overnight). The soaking process is important as this time allows the porous clay balls to begin absorbing water. This benefits the plants giving them immediate access to water once transplanted.
How much water do plants need in leca?
For a rule of thumb 1/3 of the container that the leca sits in should be filled with water. This gives your plants an abundance of water whilst maintaining high oxygen levels. You will find that as your plants roots grow, they will develop ‘fluffy’ white roots where they are completely submerged. These are known as ‘water roots’ and are perfectly healthy.
Water should be topped up or changed as the water level drops by half. This should be approximately 3-4 weeks, this is subject to change depending on positioning and time of year. Ideally water should be topped up to the 1/3 mark.
As previously mentioned leca contains no nutrients, this means additional fertilizers and nutrients will be required. Liquid based fertilizers and nutrients are the best option as they easily dilute in water. For general use, hydroponic fertilizers are acceptable, however there are some indoor plant specific fertilizers which are more ideal.