I have two Dendrobium orchids which flowered last year, I re potted them and found all the small roots were very dry and just broke off the plant, the plant stems are firm and look green under the grey outer what am I doing wrong.
Dendrobiums have shorter roots for the elongated size of their canes. The top growth is quite heavy and long, and we tend to look at the tiny pot and wonder how they ever grow. Reacting in tender loving care towards what we think is a suffering orchid, we repot it into a pot that is vastly larger than it needs. Dendrobium’s roots need to be root-bound and under-potted for several reasons. If they don’t adhere to the sides of the pot, the long canes will not have the stability they need. This can cause the pot to topple over. If you want, you can add rocks to the bottom of the pot for additional weight. Terracotta pots are excellent choices for dendrobium’s roots because they provide both the stability, cooler temperatures, and higher humidity that some Dendrobium species require. Always stake your Dendrobium orchid, especially after a repot. The orchid’s roots aren’t deep or strong enough to support the weight or height of the canes. Staking guarantees your orchid won’t be shaking around in the pot, destroying or damaging new roots.
"What is hateful to you, do not do to your neighbour".
So I suspect if you anchor it well, ensure what little roots it has are in contact with good potting medium (course and well aerated e.g. orchid bark) it should be OK.
"What is hateful to you, do not do to your neighbour".
Are they in an opaque pot with the correct medium and drainage holes ? How often do you water ( rain water is best ) and how ( soak/dribble ) and do they get decent light ? I've been growing them for several years and once they have finished flowering ( usually Feb to March ), I put them outside in a sheltered spot until frost is threatened as they benefit from a cold period. Perhaps a photo of yours may help with advice
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Dendrobium’s roots need to be root-bound and under-potted for several reasons. If they don’t adhere to the sides of the pot, the long canes will not have the stability they need. This can cause the pot to topple over. If you want, you can add rocks to the bottom of the pot for additional weight. Terracotta pots are excellent choices for dendrobium’s roots because they provide both the stability, cooler temperatures, and higher humidity that some Dendrobium species require.
Always stake your Dendrobium orchid, especially after a repot. The orchid’s roots aren’t deep or strong enough to support the weight or height of the canes. Staking guarantees your orchid won’t be shaking around in the pot, destroying or damaging new roots.
I've been growing them for several years and once they have finished flowering ( usually Feb to March ), I put them outside in a sheltered spot until frost is threatened as they benefit from a cold period.
Perhaps a photo of yours may help with advice