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Aerial roots that will not go into the pot

Discussion in 'Orchid Culture' started by Ricardo, Sep 16, 2019.

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  1. Ricardo

    Ricardo Slave of demanding bird

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    Nowadays when most people start growing orchids, their first experiences are with hybrids that have been tamed to behave in a reasonable civil manner when grown into a shelf cheek by jowl with dozens of other plants. These plants tend to keep their roots decently tucked into their pots. When orchid newbies start growing species they discover that the roots of some species will not behave as expected and will grow in any direction but into the pot. This is completely normal, roots that grow into the air are called aerial roots and their role is to absorb moisture from the environment and sometimes to catch leaf littler to form a basket from which the plant can derive moisture and nutrients. In the photo you can see a plant of Oncidium altissimum with roots growing in two totally different directions. This plant was growing on a branch that broke. However the branch was covered with so many epiphytic plants that the roots of those plant kept the branch hanging from the tree. The Oncidium plant ended up hanging upside down. The plant rotated its direction of growth 180 degrees and produced an new upright pseudobulb, which produced a new set of roots oriented to the new up direction.
     
    Last edited: Sep 16, 2019
  2. Ray

    Ray Orchid Iconoclast Supporting Member

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    I have an add-on theory about the utility of aerial roots - mechanical stability. I've seen this primarily with phalaenopsis, but it would seem applicable to other monopodials, as well.

    Such plants have a relatively small base supporting a large mass above. In the case of phals, those broad leaves can act as tremendous "sails" in the wind and exert enough force on the narrow base to literally break it off if flexed enough. Aerial roots, emerging from higher up within the structure of the plant, can act as "guy wires" to stabilize the plant.

    I did some experiments with plants in semi-hydro culture, putting them in pots at least as large a diameter as the leaf span, and every one of them sank the aerial roots into the medium, rather than continuing to "reach" outward. (Don't try that with a medium other than LECA, as the soppy part in the middle of the roots will suffocate them.)