Rockwool, also known as stonewool, is one of the most popular hydroponic growing media available.
It’s inexpensive and easy to find, so it’s no wonder why so many farmers use it.
In this article, you’ll learn about rockwool and how to use it in your hydroponic system.
First, let’s cover a little background information.
Growing media are used in hydroponic systems, rather than soil.
But they aren’t a true substitute, since they don’t have any nutrients and can’t grow crops on their own.
Instead, a growing medium is used to support the roots and stem of the crops.
So, while the growing medium acts like soil, the nutrient solution is the true substitute in hydroponics.
Rockwool is a porous manmade material, made of spun basalt rock fibers.
Growing media are typically porous, in order to have pockets for holding oxygen and nutrient-rich water.
Farmers love rockwool, because it has a high capacity for holding water.
This means, it soaks up nutrient solution easily and doesn’t dry out quickly.
Plus, even though it holds a lot of water, it still drains well, which is essential for preventing overwatering problems.
Unfortunately, rockwool is not biodegradable, so if you’re trying to be as environmentally friendly as possible, a different medium might be better for you.
Rockwool is popular both as a permanent growing medium and as a seed starter.
You can transplant seed starter cubes made from rockwool directly into your system for permanent use, or you can put them in a new growing medium altogether.
You can also start crops in rockwool cubes with cuttings.
Before you start growing with rockwool, you need to soak it in pH 5.5 water.
Small seed starters only need to soak for about 30 seconds, but larger cubes can take up to 30 minutes to be fully saturated.
Then, you’ll want to shake out any excess water from the cubes.
It’s important that you don’t squeeze out the water like a sponge.
Squeezing rockwool damages its tiny air pockets, that are essential for delivering oxygen to plant roots.
Once your crop’s roots are exposed on the bottom and outside of the cube, you’ll know its time for an upgrade.
You can either place the smaller cube directly in, or on top of a larger one, or you can place it in a new media, like coco coir.
While your crop grows, you should place a covering over any exposed parts of the rockwool.
This will prevent algae from growing, as the light won’t be able to hit the surface.
Rockwool usually comes in cubes with a hole for the plant to be placed in.
But some rockwool is sold in smaller chunks for a loose medium, like clay pebbles.
In this case, you can place the plant amongst small, loose cubes rather than inside of one larger one.
Rockwool is a great option for hydroponic growing.
We even use it for the hydroponic systems, in our Pure Greens Container Farms!
If you’re interested in learning more about hydroponic farming, visit our website or call 602-753-3469.