Calcined clay, LECA (Lightweight Expanded Clay Aggregate), and fluval stratum are all commonly used propagation mediums for cuttings. Each medium has its own unique properties and benefits, and certain types of cuttings and leaf cuttings may benefit more from one medium over the other.
1) Calcined Clay
Calcined clay is a lightweight and porous medium that is made by heating clay to a high temperature. It has excellent water retention and drainage properties, making it ideal for rooting cuttings that require a lot of moisture. As a soil amendment, it works exceptionally well for succulents and cacti. Calcined clay also has a neutral pH level, which makes it suitable for a wide range of plants. Calcined Clay can also be used as a top dressing for some plants, retaining moisture but allowing for airflow still, and without the risk of organics molding on the surface.
2) LECA & Geolite
LECA, shortened for lightweight expanded clay aggregate, is a medium made by heating clay to a high temperature and then expanding it with a small amount of water. It is lightweight, sterile, and pH-neutral, making it ideal for rooting cuttings that require good drainage, such as succulents, cacti, and other drought-tolerant plants. LECA is used heavily in hydroponics and by hobby growers alike. It’s ability to transfer water between itself and aerate roots is spot on for many applications! Some people will choose to grow plants solely in LECA, but this requires the use of supplemental nutrients. Don’t make that mistake of not simulating soil nutrients in your hydroponic experiments. LECA provides zero nutritional value to plants. Finally, if you’re a fan of stepping on your children’s LEGO blocks, this one’s for you! Nothing hurts worse than stepping barefoot on spilled aggregate. If you prefer a darker color and more irregular shapes, Geolite offers the same benefits but has a more unique shape and color. Made from the same process just a different color Clay Base.
3) Fluval Stratum
Fluval stratum is a volcanic substrate made from a mixture of natural materials such as clay, peat, volcanic silt, and other organic matter. It is rich in nutrients, promoting a healthy root development, and it has a high water retention capacity, making it ideal for propagating cuttings that require a lot of moisture and nutrients, such as tropical plants, ferns, and other shade-loving plants. Stratum does provide nutritional content to plants similar to or exceeding that of potting soil, so you won’t need to add additional chemicals to balance nutrients like neutral aggregates. Aeration is still strong with this one, and I find it to be best suited for humidity loving cuttings. It offers more surface area coverage on cuttings and provides nutrients directly as they take root. You can easily transfer rooted cuttings and leaves directly to soil with this.
In conclusion, all three propagation mediums, Calcined clay, Leca and Fluval stratum, have their own unique properties and benefits, and each medium is suitable for different types of cuttings. Calcined clay is great for cuttings that require a lot of moisture and good drainage. Leca is ideal for cuttings that require heavy drainage, and other drought-tolerant plants. Fluval stratum is perfect for propagating cuttings that require a lot of moisture and nutrients, such as tropical plants, ferns, and other shade-loving plants. A must have for terrarium growers.
There are many other uses for all of these products, from top dressings to amendments to adjust soil functionality, each one serves its place in your gardening stash!