Expanded clay aggregate

The heating process causes gases trapped in the clay to expand, forming thousands of small bubbles and giving the material a porous structure.

LECA was developed about 1917 in Kansas City, Missouri, to the production in a rotary kiln of a patented expanded aggregate known as Haydite which was used in the construction of SS Selma, an ocean-going ship launched in 1919.

In the construction industry, it is used extensively in the production of lightweight concrete, blocks and precast or incast structural elements (panels, partitions, bricks and light tiles).

Only the very bottom of the pot needs to touch this reservoir; the LECA, being porous by nature, gradually wicks moisture and nutrients up and becomes saturated, allowing the plant to feed and drink at a consistent rate.

One of the main differences between semi-hydroponics and more advanced hydroponics is the nutrients and water--whether they are consistently being delivered or whether they are sitting beneath each plant, gradually needing to be replaced before evaporating or becoming stagnant.

every 7-10 days); more advanced systems provide constantly flowing, filtered, nutrient-enhanced water over the plants' roots, which typically drains into another reservoir for recycling and reusing.