Talk me through Den. Nobile, please

[mykl]

I picked up a few scatterings from hobbyists that have had to give up on raising orchids.
Several dendros appear to be nobiles and I have no experience. Is their overwintering caused more by cooler temperatures or the change in the light availability?

In other words, would they still require a dry/ rest period if kept indoors where the temperature is relatively constant?

Would artificial lights change their habits?
TIA

[Roberta]

Nobile-type Dedrobiums have reputation for needing a dry winter rest. That means a lot less water, but not "none". They want more light than they got in summer.

Think about the habitat for Den. nobile... in summer, there are monsoonal rains. Wet, warm, and cloudy (so reduced light). In winter, there is little rain, but it's still humid and there is dew. So they still get some moisture. Since there aren't a lot of clouds, it is brighter, as well as cooler since they typically come from higher elevations.

In the house, it may be difficult to get "cool" though you could put them near a window which would be cooler.. Supplemental light would be helpful. Winter indoor heating is likely to drive the humidity down, so some light watering every week or two would be beneficial. Orchid-growing, especially indoors, is likely to be a compromise, you want to capture as many elements of what the plant would encounter in nature as you can.

[estación seca]

Flowering in these hybrids is triggered by 6 weeks of nights below 55 F / 12C and no fertilizer past late summer. If you give cool nights they flower even if watered. Without the cool nights they won't flower, not even if you dry them out. If you fertilize too late in the season they make new plantlets rather than flowers.

Have a look at the links I posted in this thread:
First Den Nobile's - Looking for advice.

[mykl]

thank you both - now I have something to go on-it sounds like they are going back outside except for the really cold nights. Our nightly low for December is just around 55F. We'll see what the winter brings!

[Roberta]

Originally Posted by mykl

thank you both - now I have something to go on-it sounds like they are going back outside except for the really cold nights. Our nightly low for December is just around 55F. We'll see what the winter brings!

Where are you located? Den nobile and its hybrids can easily tolerate temperatures into the low 40's F, and even into the mid 30's if they can warm up during the day. If they have been outside, they'll be fine leaving them there as long as night temps stay above freezing.

I'm in coastal southern California. Winter night temperatures are routinely in the low 40's F, occasionally colder but frost free. I don't dry out my deciduous and semi-deciduous Dendrobiums at all - they get watered along with everything else, get rained on, and bloom just fine. When it rains, it's a bit warmer due to the cloud cover, when it is clear and cold, typically it is dry.

[alecStewart1]

I have 2 little nobile den, Dendrobium moniliforme "Kouga" and Dendrobium hekouense.

From what I've read, you should let the medium these guys are in/attached to dry out completely during winter before watering again. Don't bother with fertilizer during winter. They'll lose all of their leaves and flowers, and you'll probably wonder if they're dead but fret not, they're just resting. Just make sure the pseudo-bulbs stay nice and firm, and not squishy or crinkly.

They like moderate to brighter light, so I would think under T5 grow lights that are about maybe 3 feet away from the tallest point of the plant or a Southwest/Southeast facing window or yard would be good.

50% humidity in winter may be fine as a minimum, but you'll probably want it to be 60-65%. Spring and summer the humidity should be like 70-80%, but keep in mind that grouping plants together can help with humidity some.

If you have Den. moniliforme or Den. hekouense, they're resilient little guys. They probably won't wither away and die overnight unless you've done something really stupid or there was mold you somehow missed seeing for like 2 weeks.

EDIT: Again, this is just from what I've read.

[Ray]

It isn't just a matter of "don't bother with fertilizer", you shouldn't apply it at all.

"Winter rests" are usually cooler period with very little rain. No rain = no nutrients being washed down onto the plants. As Roberta pointed out, that doesn't mean "totally dry", either, as early morning dew helps keep them hydrated.

Folks who grow these in semi-hydro culture typically keep them watered all winter, but apply no fertilizer until new growth has emerged.

[alecStewart1]

Originally Posted by Ray

It isn't just a matter of "don't bother with fertilizer", you shouldn't apply it at all.

Yes, sorry, that's what I meant by "don't bother."

Originally Posted by Ray

As Roberta pointed out, that doesn't mean "totally dry", either, as early morning dew helps keep them hydrated.

Yea, I was just speaking on what I've read.
I'm guessing that "dry out totally between waterings" is based on trying to limit watering during winter without letting the plant stay completely dry throughout the entire winter. It's probably what a lot people who grow them indoors have done.

My Den. moniliforme "Kouga" gets this treatment. It's oddly held on to a few of it's leaves and it popping out a new little yellow pseudo-bulb with leaves even though it's been by the windowsill where it's a smidge drafty and it's gotten down to 33 outside here. So I guess there's wiggle room with watering during winter for that species.

The Den. hekouense I let get mostly dry before watering, but I have let it get more dry a couple of times and so far no changes. It did pop out a tiny pseudo-bulb out of another bigger one not long after I got it. One bulb has been stubbornly holding on to one leaf, but it's slowly letting it go, almost begrudgingly.

Originally Posted by Ray

Folks who grow these in semi-hydro culture typically keep them watered all winter, but apply no fertilizer until new growth has emerged.

Hmm, didn't know these could be grown semi-hydro. That sounds like it would be interesting to try.

[Roberta]

Alec, don't believe everything that you read, or take it too seriously to heart. I killed some nice plants early in my orchid career, believing the "no water from Halloween to Valentine's Day" bit that I heard in all the "orchids 101" sessions. I learned. And knowing something about habitat also lets one interpret the "why" of the advice. Seeing what experienced growers do is also handy. I have spent a fair amount of time wandering around Andy's Orchids shadehouses. The Dendrobiums are in with everything else. It would be impossible, with a few hundred thousand plants, to give each one separate treatment. Plants are organized by temperature needs, all the cool-growers in the same facility. They get watered, and they also get fertilized (since fertilizer is injected into the irrigation water, it may be reduced in winter but not eliminated, not specific to any particular genus) . But they also get cold - temperatures are pretty much the same as at my house. That seems to be all they need to bloom. Because they do. Now, most are mounted so they dry fast. Andy has about 3/4 million plants, in several thousand genera. The warm growers, and intermediate ones have their own greenhouses, the ones that can tolerate cold have overhead shelter (mostly) but ambient temperatures. I think he knows what he's doing...There is a lot to be learned by observation. (The Catasetinae have their own dry little corner, but he doesn't have all that many... they don't fit well into the overall scheme)

[alecStewart1]

Originally Posted by Roberta

Alec, don't believe everything that you read, or take it too seriously to heart. I killed some nice plants early in my orchid career, believing the "no water from Halloween to Valentine's Day" bit that I heard in all the "orchids 101" sessions.

Sure, but I'm not doing that myself nor am I suggesting not to water for extended periods.

Originally Posted by Roberta

And knowing something about habitat also lets one interpret the "why" of the advice. Seeing what experienced growers do is also handy. I have spent a fair amount of time wandering around Andy's Orchids shadehouses. The Dendrobiums are in with everything else. It would be impossible, with a few hundred thousand plants, to give each one separate treatment. Plants are organized by temperature needs, all the cool-growers in the same facility. They get watered, and they also get fertilized (since fertilizer is injected into the irrigation water, it may be reduced in winter but not eliminated, not specific to any particular genus) . But they also get cold - temperatures are pretty much the same as at my house. That seems to be all they need to bloom. Because they do. Andy has about 3/4 million plants, in several thousand genera. The warm growers, and intermediate ones have their own greenhouses, the ones that can tolerate cold have overhead shelter (mostly) but ambient temperatures. I think he knows what he's doing...There is a lot to be learned by observation. (The Catasetinae have their own dry little corner, but he doesn't have all that many... they don't fit well into the overall scheme)

That's all well in good, but this starts to dip into paralysis by analysis for beginners a little.

I don't doubt anything Andy, you or any of the other senior members say on this site in regards to culture, and it goes without saying that y'all definitely know far more than me. But when we have like 3, 4, 5 variations on advice for culture it starts to get difficult for new people to figure out what they should do.

Examples: I've seen that using hydrogen peroxide is bad, but also it's fine, but also it's only fine in small doses or in particular applications, it's done their plants in and it's not harmed their plants at all. Same with cinnamon: it's effect, it isn't effective at all, it's not all that effect.

So in this case, when giving advice for nobile Dens, what do we tell a new person to do for watering in winter?

Do we say to let the medium get dry, not totally dry, it's fine if it never gets dry, it's not good to let it get dry?

For fertilizing in winter, do we say to not do it at all, only do a little, do the regiment that Ray recommends with K-Lite but half the resulting PPM and only do it once a month?

I understand we're all nerds here about this stuff, and there's a lot of "well yes but no"'s, but there should at least be a basic culture for people to follow.