The concept of growing plants without traditional potting soil, known as semi-hydroponics, has gained significant attention from indoor gardeners. This method relies on inert substrates to provide stability and deliver water and nutrients from a reservoir to the plant roots. Two popular substrates used in this system are Lightweight Expanded Clay Aggregate (LECA) and Lechuza-PON (PON). Both offer a cleaner, pest-resistant alternative to soil, but their distinct compositions lead to different outcomes for the plant. Comparing these two media helps determine the ideal substrate for specific plant care needs.
Composition and Physical Structure
LECA, or Lightweight Expanded Clay Aggregate, consists of clay pellets baked in a high-temperature rotary kiln until they expand. This process results in lightweight, highly porous clay balls, typically 10 to 18 millimeters in diameter. The expanded interior contains numerous air pockets, which contributes to their light weight and aids in root aeration.
PON is a pre-mixed mineral substrate featuring pumice, zeolite, and lava rock. Unlike the uniform spheres of LECA, PON particles are generally smaller and more irregular, creating a denser medium. Zeolite, a naturally occurring volcanic mineral, gives PON a unique chemical advantage. The lava rock and pumice provide stability and porosity, and the varied particle sizes contribute to a different air-to-water ratio compared to LECA.
Water and Nutrient Delivery Mechanisms
The primary functional difference between the two substrates lies in how they manage moisture and nutrient delivery. LECA relies heavily on capillary action, wicking water upward from a reservoir into the dry substrate. This ensures moisture reaches the roots, but LECA is chemically inert and offers no inherent nutrients. Therefore, the grower must consistently add a complete, dissolved hydroponic nutrient solution to the reservoir.
PON is formulated to provide a buffered and steady delivery system due to the inclusion of zeolite. Zeolite has a porous framework with a net negative charge, allowing it to absorb and hold substantial amounts of water and nutrients. This mineral slowly releases stored nutrients and moisture back to the roots on demand, acting as a pH buffer. While PON still utilizes capillary action, the internal nutrient buffering means a slow-release fertilizer is often coated onto the particles, providing a nutrient supply for six to twelve months before external liquid feeding is necessary.
Maintenance and Longevity
The maintenance routines for LECA and PON diverge significantly. LECA is a pure, inert ceramic that does not break down or degrade, meaning the pellets last indefinitely and can be reused after cleaning. Because LECA provides no nutrient buffer, it requires regular flushing, typically once a month, to wash away accumulated mineral salts and fertilizer residue. This prevents root burn or nutrient lockout.
PON’s longevity is tied to the depletion of its integrated slow-release fertilizer and mineral composition. The pumice and lava rock components are structurally stable and will not degrade. The built-in fertilizer is fully utilized within six to twelve months, necessitating supplementary liquid fertilizer or a top-dressing of new granules. The zeolite helps stabilize the pH, which reduces the frequency of full-substrate flushing required to mitigate salt buildup.
Suitability for Different Plant Types
The physical and chemical differences make the substrates better suited for different types of plants. LECA is recommended for plants that favor excellent aeration and can tolerate a slight wet-dry cycle between reservoir top-ups. Many aroids, such as Philodendrons and Monsteras, adapt well because their chunky root systems benefit from the significant oxygen exchange provided by the large spheres. Orchids and other plants prone to root rot thrive in LECA’s high porosity.
PON, with its finer particle size and nutrient-buffering zeolite, is preferred for plants requiring consistent moisture and a stable nutrient environment. Fine-rooted plants, such as succulents and smaller houseplants, establish themselves easily in the denser particles of PON. Its capacity to hold and slowly release nutrients makes it a reliable choice for plants that benefit from a continuous nutrient supply.