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Mineral-based and/or Inert Substrate Only?

Discussion in 'Orchid Culture' started by Another_World_Terraria, May 30, 2021.

  1. Another_World_Terraria

    Another_World_Terraria New Member

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    Is anyone experimenting with 100% mineral-based and/or inert substrates for lithophytic orchids such as limestone-dwelling Paphiopedilum spp? I realize that this idea conflicts with most advice and practice, but I like to think outside the box and experiment

    My understanding is that Paphs are typically grown in a mix with bark, etc, but I was thinking of trying a limestone-cliff species using only mineral elements (of which there are both acidic and alkaline options that could be mixed).

    Theoretically, as long as the pH matches that of the species natural preferences, the nutrients are delivered via fertilizer, and the substrate is flushed well, this could work, but I have no experience with this idea.

    My goal would be to significantly increase longevity and reduce repotting and root decay.

    Any info would be appreciated.
     
  2. Roberta

    Roberta Active Member

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    Remember, lithophytes don't grow just on the surface of rocks, though some roots certainly cling to them... roots tend to grow into crevices that have organic matter - leaf detritus, etc. They also get moisture in those cracks. So they don't grow in a purely inorganic environment.
     
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  3. KellyW

    KellyW Orchid wonk Staff Member Supporting Member

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    I have used LECA extensively and frequently used it as 100% of the medium or sometimes with perlite. I like it for medium to large plants and felt it provided excellent conditions.
    However, it sounds like you are growing in a terrarium and thus probably small to miniature plants. If that is the case then LECA may not suit your needs.

    Roberta is correct about the organic matter in rock crevices. However, I doubt that it is essential to recreate that condition artificially. I suspect the biggest issue will be adjusting your watering and finding the right mix to allow plenty of air getting to the roots.
     
  4. Ray

    Ray Orchid Iconoclast Supporting Member

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    There is a big difference between natural rock outcroppings and LECA. Rocks tend to be essentially non porous, which is why lithophytic plants sink their roots into the cracks and fissures where organic matter and moisture accumulate. The relative lack of porosity and accompanying insolubility means the rocks will dry fast, will not accumulate residues, and probably don’t do much in the way of providing nutrient ions.

    LECA is porous in its own right, and while it might be chemically inert, it’s ability to absorb and hold solutions make it more of an “active participant” in the plant’s environment than are rocks in nature. Unfortunately, that porosity also leads to the gradual buildup of residues, especially if allowed to undergo significant drying between waterings, so it will become toxic over time, and require replacement.
     
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