How do you cut the resting period of Dendrobium

[dejpep]

I have a problem with the Dendrobiums. They grow very well wile they are outside but when I have to bring them in, when the temperatures starts to go down, they wont grow a spike, and even if they do, the flower buds will fell of before they develop. The reason for that is I think because the air inside the house is very dry and the length of the day is too short. After that they go in dormant stage. I want to ask you how do I wake them up from the dormant stage, so by the time when I have to take them outside they will be already growing. That will increase their growing time outside and I hope they will develop a spike at the end of the summer. Thank you.

[kmarch]

Hello dejpep and welcome to the forum!

Before we can address your questions, we need a bit more info:
1) What part of the world are you in? - in some parts of the world dens can be grown outside and need no special attention, in other parts they need to be cared for differently.

2) What kind of dendrobiums have you got? - the genus dendrobium is a huge genus, more than a thousand species and thousands of hybrids. Different tryps require slightly different conditions (some dramatically different). It's difficult to give advice when we don't know what kind of dens you have.

[dejpep]

I live in New Jersey and I'm not sure what kind of dendrobium it is. I think is Dendrobium phalaenopsis. It's the one that produce flowers at the top of the new growth. Here are some pictures :

[kmarch]

Yeah these are phal-type dens, whether they're the species Den phalaenopsis (properly called Den bigibbum) is another matter (did they come tagged?)

Originally Posted by dejpep

I want to ask you how do I wake them up from the dormant stage, so by the time when I have to take them outside they will be already growing. That will increase their growing time outside and I hope they will develop a spike at the end of the summer. Thank you.

Phal-type dens (as you've noted) grow and bloom according to a distinct cycle. They grow in spring/summer, growths mature in autumn, and they spike/bloom in winter after which they have only a short rest before starting the cycle all over. Their normal spiking time is in winter when the temps drop a little and it's a little drier. The end of summer is not their spiking season and unless you somehow make the summer feel like winter, they're not likely to spike at that time. You'll notice that your growths are maturing just like they should in the summer/autumn. They're reaching maturity as it is (which is necessary for flowering) so getting them to start growing earlier won't affect their flowering.

These dens don't need a really cool period like nobiles and are mostly intermediate growers (55-60F winter minimum) with winter being toward the cooler end and drier. How late do you bring them in? What are the temps getting down to when you bring them in for the winter? Are you using highnitrigen fertilizer on then in late summer or autumn?

It is likely the hot dry climate in the house causes the bud blast.

My recommendation is forget trying to get them to start growing sooner and examine your autumn/winter culture to see what the cause of no blooms might be. Check the American Orchid Society for a phal-type culture sheet that may shed further light on your autumn/winter culture.

[dejpep]

Dendrobiums are not the only orchids that I have that are dropping buds. I have very same problem with Phalaenopsis too. Here are some pictures of them

[kmarch]

Phals are even more succeptable (sp?) to bud blast, as caused by a change in conditions, than dens are. We frequently hear from members who just brought home a new orchid only to have all of its flowers drop off right away. They can drop from a condition change as small as a draft on the windowsill and both den and phal flowers/buds, actually most orchid flowers, don't respond well to hot/dry environments.

[dejpep]

I bring them in in October, when the night temperatures start to drop in the upper thirties . I also have mini dendrobiums and they do not grow very big and by the end of August they start to grow a spike, and by the end of September they are in full bloom. But the other ones just can not stop growing. Last year one of them grow more then 2 feet. And they continue to grow until it starts to get colder, and that is the time when I have to bring them in(no choice). After that change of climate and no spike. That is why I thought if I can make them to start growing now somehow with an additional light, maybe they will finishes growing by end of august, like the mini dend. and there will still time for them to develop a spike in Sept.
Maybe I'm wrong. I don't know.

[kmarch]

Originally Posted by dejpep

I bring them in in October, when the night temperatures start to drop in the upper thirties .

Is this true for all of your orchids or just the phals? Actually it doesn't matter because dropping into the upper 30's is too cold for both phals and phal-type dens. Neither should be allowed to get below 55-60F.

I suspect this might be part of the problem. The plants are getting cold shocked and shutting down. Take them in earlier. I think they'll do better.

[11Orchid126]

Unlike dendrobium nobiles, the dendrobium phalaenopsis types do not go into a dormant stage in the winter. True, fertilizer is cut back as is water, since the light is so low. But they still need bright light and a bit of fertilizing and regular watering during the winter months. It sounds like you put them into dormancy somehow. Start giving them water and let them dry out before giving them more, and after a couple of weeks of plain water add a bit of fertilizer to it. By April the plants will be in their regular growing season and can take lots of water, fertilizer and as much sun as you can give them without burning the leaves.

[dejpep]

Well I was afraid, since they are not growing, that will hurt their roots by over watering them and maybe that is the reason why they went to sleep. I'll start to water them once every two weeks and I hope soon a new growth will appear at the base of the plant.
Thank you guys for all your help. I will still check the forum for other things I need to know.