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Agar question


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I never have used agar before and I want to know how firm does it have to be for use as medium.

I'm assuming too hard will stop the roots from getting in it and not firm enough would let the plants sink in it.

Edited by carnivoor
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The amount of agar needed to provide a supportive gel needed depends on its quality grade. Most of the time 5-7g/l concentration is used. I use Sigma-Aldrich agar and the amount I like to use is only 4g/l. When the agar gel is too hard, the problem is that the nutrients transfer kinetics is too slow to diffuse fast enough. Most of my plants do not have any roots in media or start to develop them later, about after 2 months of growth. Usually I let them root directly in peat during the acclimatisation.

On the other hand, when the agar gel is too weak, it is not very bad thing, except for easier precipitation and sedimentation of nutrients. Personally I like to use weak agar solutions, some species even like semi-liquid media better than hard gels. It is not harmful for the seed, seedling or plant to be completely submerged, since they dont consume aerial CO2 anyways.

Some nepenthes (and other species) are best grown on media with no agar at all, and for support cotton cylinders or sterilised gravel, sand or pebbles can be used to a great advantage:-)

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