Here, I’ll discuss what water rooting is and why it’s important for LECA. If you just want to skip to how to water root something, click here.
Not all roots are created equal in the LECA community. The two most common types are soil or water roots.
Soil Roots versus Water Roots
Soil is the roots that grow into, you guessed it, soil. They are generally delicate and do not like to be submerged in water for long periods. This is how you kill soil plants, or at least how I always did: you overwater it and make the soil roots sit in water (you had the best intentions, but it’s so hard to tell when enough water is enough) and when soil roots get wet and stay wet, they rot. Quickly.
By contrast, water roots grow in water; they have no problem being submerged in water; in fact, they prefer it. They are thicker and yellow/white in color and generally more resilient. These are the roots you need to use with LECA successfully.
Capillary Action
Water roots use capillary action; you probably learned about it in earth science; it just means it takes water from a lower source and brings it up using a medium. Think of a paper towel in a glass of water; eventually, the water will go up the paper towel, even if only its bottom is submerged.
In the case of LECA, it helps the water roots carry water up from the bottom of the pot. It needs water roots to do this; it’s a team effort. This way, it keeps the roots moist, but the LECA allows air to get to the roots, making rot a thing of the past.
How much water is too much water?
If done correctly, the water roots should just touch the bottom of the water level of the vessel. Eventually, these roots will grow, and they will grow down into the bottom of the vessel and end up being fully submerged in water. This is ok because they are water roots; they can handle constant water, and that’s how they were grown originally. Some people have trouble with this concept because it seems counterintuitive.
Starting off, only let the water touch the bottom of the roots, but once the plant decides to grow and pushes roots down into the bottom (full of water part of the vessel), don’t stress about it. The plant decided to do it, and it was fine as long as it was the plant’s choice. This sounds silly, but it’s true. Let the reservoir go down to almost empty before refilling it, in this case, to let those roots dry out.
This is not a perfect science; it doesn’t need to be; just keep in mind that at some point, oxygen needs to get to the roots to lessen the risk of rot, so letting a plant mostly dry out some before refilling it is ok as long as you are paying attention.
Oxygen is important for roots; they need access to it at least sometimes to prevent roots. This is why some people water their plants with some hydrogen peroxide mixed in; it increases oxygen to the roots.
Transition from Soil to LECA
Water roots are generally essential for LECA. You can water root a cutting in water before putting it in LECA, or you can stick a plant with soil roots into LECA and cross your fingers that it goes well. This skips a step but has a higher risk of losing the whole plant to root rot. I do both; generally, if it’s a plant I care about, I will always water the root first, even though it takes longer. There are so many different ways to prop cuttings to get them ready for LECA. There are more details here; it’s easily the most complicated part of plant keeping, but it’s also gratifying.
I have posts on how to take a cutting, how to propagate, root rot, and how to transition soil plants, all of which should help you with this LECA transition/water rooting process. It can seem complicated, and there is some trial and error here; you might lose a cutting or plant or two in the learning process, but it’s so worth it in the end. I lost many plants during the transition to LECA. Still, now I have happy and healthy plants that are easy to care for since LECA is low maintenance once it’s established.