Source: Own work


Seramis is a substrate made of small porous clay granulates that absorbs water easily and then delivers it to the plants as needed.

Fertilizer is added to the water, just like for any type hydroponics.

The water absorption capacity is quite high: 100% of its own weight without any change of volume.

This means that on average (depending on the type of plant and environmental factors) it contains enough water for 3-4 weeks.

But it is supposed to be used with a moisture meter. Without this moisture meter, it’s any body’s guess when you need to water.

And… we’re back to square one: as with culture in soil, knowing when to water looks more like guess work than really knowing when a plant needs watering.

Orchids and bonsai don’t need a moisture meter. Either you water with small amounts on a regular basis, either you immerse the plants with pot and all in a nutrient solution, about once every two weeks.


  • very porous, retains water very well (100 % of its own weight)
  • very light
  • chemically inert
  • structurally stable
  • plants don’t need to be repotted as often
  • great for orchids and bonsai
  • can be used outdoors
  • great for sowing


  • without a moisture meter, knowing when to water is as difficult as with soil culture
  • expensive: double the price of hydroton clay pellets


Seramis substrate is especially suited for orchids and bonsai.

For other plants only when combined with the moisture meter.

May be used outdoors.