Dendrobium cuthbertsonii flowers don't open up wide

[Wendelin]

The Dendrobium cuthbertsonii, marc shows in this thread http://www.slippertalk.com/forum/showthread.php?p=303700#post303700, I'd like to see in my house .
I bought my cuthbertsoniis with flowers that are wide open like the ones shown there. Now they bring out lots of new flowers but they open up only half way and stay there .I just don't know why!

They get good light, the best water,perfect airflow, ones in a while light fertilizer, and I just dont know what I have to do, so they'll show their whole beauty!
Anybody, who gets an idea, please step forward!

 

[SlipperFan]

I'm not sure they open much more than that. Take the photo from straight-on, and see what it looks like.

 

[goods]

I don't have any experience with cuthbertsonii (hoping to attempt one soon), but I know other orchids' flowers are affected by humidity levels. How high is the humidity around the plants?

 

[Wendelin]

Thats the plant when I bought it

And this is how the flowers open up now

the petals/sepals just don't bend backwards. Even sometimes they open up a little wider but then they'll go back to that stage.

Humidity is from 65-85 % mostly 70-75%

 

[Marc]

What temperature are they growing at? I've been told that this is a very cold growing species.

 

[Roth]

They open up more when they get older. I found that the flowers are nicer when the plants are kept cooler, though the species itself has the false reputation of being 'cool growing'.

 

[Wendelin]

The temperatures lately have been guite cool for summer .An average of 18°C and very humid.The flowers are already open for at least 2 months now and they are not getting better.

 

[slippertalker]

They don't always do what you want them to.......I find that many orchids bloom differently from year to year, and those that bloom more often have different quality each blooming.

 

[Wendelin]

They don't always do what you want them to.......

I figured that!
It's only, if there is something I can do, I'd like to know!

 

[ChrisFL]

They open up more when they get older. I found that the flowers are nicer when the plants are kept cooler, though the species itself has the false reputation of being 'cool growing'.

??

What should it be considered?

 

[goods]

I have the same question as Chris. If this is not a 'truly' cool growing species I'd like to give it a try indoors in a tank. Could you explain what you meant about it not being cool growing?

 

[Roth]

Depending on the colonies, but many cuthbertsonii can be grown intermediate to hot for a large part of the year. Now in Hanoi it is over 30 days and night, and they do very well.

Cuthbertsonii requires a temperature drop at night, and a cold time frame of a few months around winter. I grow mine in orchiata classic grade. rockwool would do it very well too.

Sphagnum does not allow to grow cuthbertsonii warm, apparently it becomes corrupt, and releases somethign that kills them at warmer temperatures ( but do not kill many other orchid species). So cuthbertsonii gown in sphagnum must be grown cold. If you choose to try bark or rockwool, you can grow them intermediate, and even warm if you have cool winters.

 

[Wendelin]

Sphagnum does not allow to grow cuthbertsonii warm, apparently it becomes corrupt, and releases somethign that kills them at warmer temperatures ( but do not kill many other orchid species). So cuthbertsonii gown in sphagnum must be grown cold. If you choose to try bark or rockwool, you can grow them intermediate, and even warm if you have cool winters.

Thank you for that information, Roth! I'll keep an eye on that.