I've got a doubt about what would be the minimum medium space a plant needs to grow.

I'm making a hydroponic system, and I would need to know what is the dimensions of a plant's root required for it to growth without issues.

For example, let say lettuce, a lot of you know the typical rockwool cube, it is 2" x 2" normally, but, my doubt is, would a plant still grow if that cube is divided, and instead of being 2" x 2" becomes something like 3/4" x 3/4" or 1" x 1"?.

In theory, the roots go down and they have space to expand, but you know, if someone else tried this it would be great if you can share your experiences!.

1 Answer 1


The main reason for using rockwool in hydroponics is anchoring the plant crown. The plant can survive without the rockwool (The plant doesn't obtain many materials from it), but cannot hold itself up. You will start running into the same problem if you use an extremely small root hold for the plant.

Depending on your tray, or whatever support you are using, and the plant you intend to grow, I think you could get away with a 1" cube, but I haven't done it myself. Also note that even in smaller cubes, you will want to use the same plant spacing, so the only thing saved would be a little rockwool.

  • If it's just about saving some rockwool, I've grown lettuce in neoprene collars normally used for cloning, which worked fine, and unlike rockwool they are reusable.
    – Ingmar
    Jul 17, 2014 at 21:09
  • @Ingmar True. Also, the neoprene collar will do a good job supporting the plant. It wouldn't work in all setups, though.
    – J. Musser
    Jul 18, 2014 at 3:54

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