Plants roots are suspended in clay pellets so that we can run a liquid nutrient solution over the roots without leaving them in a bunch of soggy rotting muck.

Roots bathed in liquid nutrients grow into compact hairy root networks, rather than long big roots you find in soil where plants are out searching for water below ground. The hairs  grab hold of droplets of the liquid nutrients and grow into the porous cavities of the clay pellets to find tasty little juice pockets waiting for them even when the pump is turned off.

Dandelion green roots growing around and into clay pellets

The clay pellets are a great match for drip irrigation because they hold just the right amount of this stuff around the plants’ roots. No killer sog because, like rocks or pebbles, they shed water. But way better than rocks because they hold just a little bit of moisture close by for the hairs to reeeeeach out and ahhhhha get a little sip when they need it.

Clay pellets provide no nutritional value for the plant; it all comes from the nutrient solution. However, they are not made of lava rock, which would react and change the chemical composition of the nutrient solution. They are “inert,” meaning they don’t react.

Clay pellets shed water like pebbles, but their porous interior pockets hold little droplets of liquid nutrients for plants' root hairs to find

I like them because they can be reused, so I don’t have to add to the landfill with every crop. You can clean them and dip them in boiling water between crops to sterilize them.

Nothing is ever sacred and in the spirit of R&D-I-Y, it would be great to find ways of replacing clay pellets with something that was not shipped all over the world from Germany.

However, if you are new to windowfarming, I don’t recommend that these be one of the first things you start experimenting with substituting out.  Wait until you get the hang of dealing with nutrient solution first– there are plenty of other variables to change out as you get to know the microclimate of your window.

This is why we include them in the kits for new windowfarmers.

-Britta