I am trying to germinate some alfalfa (Medicago sativa) seeds in coco peat. I bought a bag of dried coco peat at a store. The coco peat consists of coconut husk pith and some coconut husk fibers. I recall some advice that germination media should be as moist as a "wrung out sponge". I am not sure how much water that is supposed to be. Does "wrung out sponge" refer to 50% moisture in coco peat? i.e. the weight of the water should be equal to the weight of the (dried) coco peat.

2 Answers 2


I suggest doing it by feel. I rehydrate compressed blocks of coco peat for soil blocks, and how much water I add varies block to block.

But to put some numbers on it, I have a block of compressed coco peat from Exotic Wood Zone in front of me. The label says to add 0.6 gallons (2.3L) of water to each 1.4 pound (635g) block, and then add more water if it is still too dry.

2.3kg water / (2.3kg water + 0.635kg coco peat)

2.3kg water / 2.935kg total mass

78% moisture by mass

Good luck with your alfalfa!

  • How do you ensure that the coco peat retains an acceptable level of moisture given that some of the moisture will evaporate throughout the day? Is it by always making sure that there is water in the germination container's saucer so that the coco peat can act as a wick to bring moisture to the seeds?
    – Flux
    May 16 at 15:19
  • @Flux I had to ask the same question :-) gardening.stackexchange.com/questions/66114/… In short, I do bottom water like you say, but I let the tray run dry in between waterings. My coco blocks are in a grow tent at 75% Relative Humidity and I re-water them about every other day. If they were more in the open I would probably water them daily. It takes a little trial and error but you figure out what works best for your situation pretty quickly.
    – MackM
    May 16 at 15:29

One approach is to soak it, in an excess of water, and then grab a handful and literally wring it out (because it's a fibrous media where you can expect that to work.)

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