Is there a reference list for Dendrobiums that do/don't go into dormancy/winter rest?

[RiverbankMudlark]

I have a D. aberrans and D. jenkinsii, and I'm going to be getting a variegated miniature D. moniliforme. I haven't been able to find a lot of information on which of these goes dormant/wants a Winter break (which I think are the same thing? I'm a bit new to Dendrobiums, so the whole Winter thing and what qualifies as a "dormancy" or "rest" or "break" is a bit confusing), as opposed to the ones that just want a cutback/reduction on water/food during the Winter.

[Roberta]

First, Welcome!

"Dendrobium" is a huge genus, and members of different sections have different needs. You really need to get down to the species level, understand the habitat of each one. A good place to start is the Internet Orchid Species Photo Encyclopedia Those from low elevation in the tropics need to be kept warm, and definitely kept damp all year around. The ones from higher elevations and/or higher latitudes (like northern India, south-central China, and high-ish elevations in southeast Asia) experience seasonal differences in temperature and rainfall.

D. aberrans is a warm-growing, tropical species. It needs to be treated the same all year. D. jenkinsii and D. moniliforme have a reputation for needing "winter rest" ... that being said, I just let them get a chill during the winter, don't dry them out, and they do fine for me. (But I'm in southern California, pretty much frost free) The fall chill may be a challenge for you, some reduction in watering (and no fertilizer) will tend to have a similar efect. But not bone-dry.

[Keysguy]

I'll add a couple thoughts.

First, I'll second everything Roberta suggested especially using Jay Pfahl's IOSPE as your #1 reference guide. Jay has to be getting close to either personally possessing or having access to every book or technical paper ever published on orchids and everything in the IOSPE is source referenced and peer reviewed. It is arranged alphabetically by genus and species. It can even be used for hybrids if you do some research into your specific plant's geneology and apply a little deductive reasoning.

Second- We don't know what your growing environment is other than you are in Canada so your growing somewhere between a windowsill and a tropical greenhouse that must be hooked directly to your private gas well, otherwise it's costing you a fortune to heat. Knowing what your conditions are is critical.

Third- IN GENERAL, the warmer your conditions, the winter water is less important to getting good blooming on the dendrobiums in question than it is to have nice bright light and eliminate fertilizer.
The reasons being are that they come from a climate where they become deciduous just like all the other plants in their habitat. No leaves = brighter light in the habitat. There is less rainfall but it is almost never "zero" rainfall. In nature, orchids feed from detritus falling out of trees like dead leaves, bird droppings, etc. which in a deciduous environment gets significant lessened in the winter by #1, no overhead leaves and #2, little rain to flush anything from the tree onto the plant.

Hopefully this makes sense.

[Ray]

For plants that DO require such a “rest”, it’s more about “no fertilizer” than it is “no water”.

[Canadienne]

My dendrobium Nobelis all get a winter rest. This means they come in the house after summering outside till late fall. We had a warm fall this year. Their rest means for me, a southern window, full sun after October, water once a week ( mine dry out by then, potted in inorganic media) and that is rain water. Their night temps are 12-15 C in an unheated bedroom. Daytime temps around 21C. None have been fertilized since September. My big Noid is now forming buds on 4 leafless canes.

[DeaC]

St. Augustine Orchid Society - North Florida Orchid Growing may be of help. Their section on Dens. is good reading.

[RiverbankMudlark]

I live on Vancouver Island, so relative humidity is very high, and depending on what source you reference, we are usually in zone 9 or 8.

I grow my orchids inside on the window sill in my room, which is positioned above the baseboard heater. I like to be warm, so usually I have the temperature at around 20°C.

Also, I generally pot my orchids with a mixture of sphagnum moss and bark (varying the proportions depending on the needs of the orchid).

[Roberta]

You might consider finding a cooler place (not over the baseboard heater) for the Den nobile and Den moniliforme. Both of those will benefit if you can give them a space near a window where it gets a bit chilly. And move them outside in the spring once nights are above 10 deg C if the days start to warm up. (And next fall, you can leave them out until nights get down to 5 deg C or so, since they will have had time to acclimate. ) The Den aberrans will be very happy with the warm spot, though. That one appreciates Phalaenopsis temperatures, though it needs more light than Phals.

[Clawhammer]

Here my list of all the winter rest plants I keep with the temp I keep them at. I stop fertilizing in mid October and resume March 1. Days between watering is basically doubled or tripled depending on species.

Name Winter Temp
Coelogyne Unchained Melody 45
Dendrobium 'Angel Baby' 45
Dendrobium 'Christy Dawn' 45
Dendrobium 'Frosty Dawn' 45
Dendrobium 'Hamana Lake' 45
Dendrobium 'Oriental Smile Butterfly' 45
Dendrobium 'Rainbow Dance' 45
Dendrobium 'Stardust 'Fire Bird' 45
Dendrobium 'Sweet Dawn' 45
Dendrobium bellatulum 45
Dendrobium brymerianum 45
Dendrobium chittimae 45
Dendrobium christyanum 45
Dendrobium draconis 45
Dendrobium hancockii 38
Dendrobium loddigesii 45
Dendrobium monofiliorme 40
Dendrobium pendulum 45
Dendrobium sulcatum 45
Encyclia citrina 45
Encyclia mariae 45
Laelia Albida 45
Sarcochilus falcatus 35
Maxillaria variabilis 50
Den. Asian Bride 'Fancy Bell' x Den. Omokage 55
Dendrobium albosanguineum 60
Dendrobium anosmum 60
Dendrobium chrystotoxum var sauvissimum 51
Dendrobium hercoglossum 55
Dendrobium lamyaiae 50
Dendrobium parishii 60
Dendrobium pulchellum 50
Dendrobium scabrilingue 52
Dendrobium sutepense 50
Dendrobium unicum 50
Dendrobium kratense 55
Dendrobium senile 50
Dendrobium 'Gatton Sunray 3-Lip' 50

[FranningtonBear]

Originally Posted by Keysguy

The reasons being are that they come from a climate where they become deciduous just like all the other plants in their habitat. No leaves = brighter light in the habitat. There is less rainfall but it is almost never "zero" rainfall. In nature, orchids feed from detritus falling out of trees like dead leaves, bird droppings, etc. which in a deciduous environment gets significant lessened in the winter by #1, no overhead leaves and #2, little rain to flush anything from the tree onto the plant.

Hopefully this makes sense.

*lightbulb* Thanks Keysguy

---------- Post added at 09:13 PM ---------- Previous post was at 09:08 PM ----------

Originally Posted by Clawhammer

Here my list of all the winter rest plants I keep with the temp I keep them at. I stop fertilizing in mid October and resume March 1. Days between watering is basically doubled or tripled depending on species.

Name Winter Temp

Dendrobium 'Sweet Dawn' 45

Sorry to hijack, do you have any pictures of Sweet Dawn? I have this plant but have not bloomed since owning.