root tips turning black

[pinett]

Hello,
this is my dendrobium amabile, put in S/H since june. It was doing well almost till november as you can see in this photo, with active root growing.
at the moment, some root tips are turning black and one leaf in the middle height of the cane is now completely and uniformly yellow.
there have been no recent change in the growing condition, good humidity 60-70%, just I think lower night temperature as it's winter here.
is it normal? thank you

[rbarata]

Not an expert in S/H neither den amabile culture but I think this plant may have a rest period. Many dendrobiums need it. During that period their growth stops and leaves turn yellow and die.
From the photo it seems the roots are dehydrated but I don't know if this is possible in S/H culture.
Maybe you should mist lightly the aerial roots just to keep them green and growing.

[jkofferdahl]

Most of the black tips you've circled are older growths and may simply be done growing. You've got some nice new growth. I'm not a S/H grower, but usually when I see roots like yours I check the humidity in the growing area before anything else; I think it may be too low.

[King_of_orchid_growing:)]

I have Den amabile. This plant definitely has a defined winter rest. Root growth will not persist throughout the winter months.

The fastest growth is from spring through mid-fall.

During winter, growth either halts completely or is very negligible.

I cannot advise you on how to grow this plant SH. I grow it with large grade bark chips. It has done well for me like this so far.

[pinett]

hello and thank for your replies.
this is my first winter with this orchid and also with S/H culture method.
This means that in the picture you can see the old brown root that are going to death because useless in this environment and the new white ones with a long green tip, (i'm sure they weren't all there in July...).so it's a bit surprising seeing them grow and turn black just in the tip...i'm not actually convinced that is a normal manifestation of aging. i was wondering if they suffer the cold in the night.

Instead for the leaves, according to you during this rest period it may loose all of them? it seems very different from d. nobile, for example.....thank you!

[Ray]

It's very difficult to analyze reliably from photos, but that second photo looks like the pot is way too dry. Growing root tips that come into contact with dry LECA particles may have the moisture drawn right out of them, killing them and turning them black.

[pinett]

Hi Ray,
so it is possible that I've to water more often instead of reducing frequency. I'll do it and follow with picture that for me are very reliable instead of my memory!
this are details of this morning
thank you:-)

[King_of_orchid_growing:)]

Instead for the leaves, according to you during this rest period it may loose all of them? it seems very different from d. nobile, for example.....thank you!

No, this is not a fully deciduous Dendrobium. It may have a true rest period, but it will retain most of its leaves throughout. If all the leaves on Den amabile are falling off during the winter, that is not a good sign.

[pinett]

hi king
I trust you, it seems there are not so much owners of this den! thank you for your clarification