What's the deal with my dormant Dendrobium?

[CJ Green]

I am so confused about my Dendrobium nobile. I bought it last summer, repotted it, and it developed buds and then flowered in the fall. I kept it outdoors until the weather got too cool, then brought it in and kept it on a sunny windowsill, where the temps got down into the low 50s at night. I thought it was supposed to go dormant so once the flowers were done I stopped watering it, but it never dropped its leaves (one or two turned yellow and dropped off but that was it). Now I have no idea what to do with it--do I need to wait for signs of growth before I start watering it again? It's May already and it seems strange to wait so long!

[Roberta]

I would resume watering. If it bloomed in the fall, it had its seasons confused... generally these are spring bloomers, but growers can mess with the pattern by manipulating temperatures to get blooms to coincide with shows, holidays, etc. So if you start watering now, you will help to "reset its calendar". Next fall, do what you did this year, and it will probably flower (more normally) in the spring.

[CJ Green]

Thanks! That's good to hear. This plant and a Clowesetum are the first orchids I've bought that have a dormant period, and I need to get the hang of it!

[Roberta]

The dormancy on the nobile-type Den is not as severe as for the Clowesetum. I have found that Den nobile and relatives do need some water through the winter, just not as much (and no fertilizer at that time) I think that giving them a a chill (50 deg F or a bit lower at night) is the bigger factor in blooming. They tend to keep leaves, especially the newer ones. The Clowesetum (and other Catasetinae) on the other hand really do need NO water once they drop leaves, until the new spring growth is well on its way. But they also don't want to get cold. That one should stay above 65 deg F at night (Phal temperatures)

[estación seca]

Den nobile and hybrids don't necessarily drop leaves during dormancy. You might notice the ones sold in shops that are loaded with flowers usually have full sets of leaves on all the pseudobulbs. These plants have been watered so they keep their leaves, and chilled so they flower.

Yamamoto Dendrobiums [had] detailed growing information on their site. This includes summer fertilizer management and winter temperature recommendations, both of which they say are very important for flowering. They recommend light winter watering, and not resuming heavy watering until new growth appears at the base.

Edit June 15 2020:
Yamamoto Dendrobiums in Japan hybridizes and produces a great number of these plants. Their Web site formerly had excellent growing information for hobbyists. Unfortunately it is no longer there. You can still look at the varieties they grow, and maybe see one very similar to yours.

I saved the page, and summarized it in a post in this thread:
Uncertain if Dendrobium is still alive

Yamamoto now has a page showing how to force Dendrobium nobile for Christmas flowering in Japan's climate. There is a lot to learn from that page, but it is intended for growers who can artificially heat and cool their greenhouses during off seasons. Note they use coconut husk for growing medium, which many orchidists would say retains too much water for orchids. For many orchids that is correct, but this is a very thirsty orchid.

[CJ Green]

Originally Posted by Roberta

The Clowesetum (and other Catasetinae) on the other hand really do need NO water once they drop leaves, until the new spring growth is well on its way. But they also don't want to get cold. That one should stay above 65 deg F at night (Phal temperatures)

Wow, that means my Clowesetum definitely got colder than is optimal for it! I'll try to keep it warmer next winter. Thanks again for the advice.

---------- Post added at 05:43 PM ---------- Previous post was at 05:38 PM ----------

Originally Posted by estación seca

Den nobile and hybrids don't necessarily drop leaves during dormancy. You might notice the ones sold in shops that are loaded with flowers usually have full sets of leaves on all the pseudobulbs. These plants have been watered so they keep their leaves, and chilled so they flower.

Yamamoto Dendrobiums has detailed growing information on their site. This includes summer fertilizer management and winter temperature recommendations, both of which they say are very important for flowering. They recommend light winter watering, and not resuming heavy watering until new growth appears at the base.

Thanks! I did water the Dendrobium a couple of times during the winter, because it just felt so weird not to water it at all. So I accidentally did the right thing. The Yamamoto information is great. I just couldn't figure out the timing since my plant was flowering when it was "supposed" to be going dormant.

[Roberta]

Originally Posted by CJ Green

Wow, that means my Clowesetum definitely got colder than is optimal for it! I'll try to keep it warmer next winter. Thanks again for the advice.

This one can easily be kept in your "living area" during its winter dormancy - with no leaves, it doesn't take up much space. It just wants to be ignored. In his Catasetum talk, Fred Clarke tells the story of a customer in New York who thought that the bare, leafless bulb was dead and just tossed it behind the couch (Why? No idea...) The following spring she was doing some serious cleaning, moved the couch, found the bulb, and Wow, it was producing a new growth! Don't throw it behind the furniture when it is dormant, but you certainly don't have to put it with the other plants that need care...