Den. Nobile uncertainty: Outdoor chill + repotting.
 

Hello All,

I have another culture + repotting question.

I have these three Yamamoto dendrobiums that I am not quite sure what to do about.

When am I supposed to repot these? Is it time now? Is it too late? Ideally, I would repot soon because the moss they are in has composed quite a bit and that isn’t good for the roots.

Additionally, I know I am also supposed to chill them outside this time of year yet they also are having new growths sprouting, maturing and some that just matured. What do I do about this? Is this also relevant to my first question about repotting also?

Den. Nobiles always confuse me.

Time to repot is when new growth starts - typically in the spring. You should be cutting back on the water within the next month or so... don't dry them totally (I have killed a few of these taking the "dry rest" advice too literally in early "orchid career") but they should dry well between waterings. If they are kept on the dry side, the "past its prime" moss won't hurt anything. As far as chill, again temper the "advice" with some common sense. They would probably like to see some cooling at night, but don't freeze them. (While the parent Den. nobile experiences frost or near-frost in its habitat, these hybrids come from Hawaii...) If they are just near a window as temperatures drop, they'll probably get the chill that they need (and also the high light... that's the other part of the dryness in habitat, less cloud cover means more light) They may drop leaves or may not. Again, these are hybrids. So don't worry either way.

Thank you for your reply.

What would be an acceptable night time low?

In the greenhouse, it gets down to the low 60s.

Outside, it goes down to the upper 40s and low 50s but typically stays around 54f.

Would 45-48f be too cold? Should I just leave them by the vents in the GH which gets to around 62f?

So far those night temps are OK, especially if it warms up during the day. However, I'd be on the cautious side, I know that weather on your area can change abruptly this time of year... watch the forecasts, you're much better off bringing it in sooner rather than risk a sudden frost. I don't think that it really needs much of a chill, the natural day-night cycle in the greenhouse is probably sufficient. And many of the hybrid Zygos have warmer-growing species in their background, all the more reason to be careful - for instance, Zygonesias are happier in the GH in general.

I may be doing things wrong, but I’ve repotted mine in the fall when I’m concerned about the media so that I don’t have to worry about bad media and disrupting the flowers when they form in the spring and I start watering again. I usually watch the canes in the winter, when the cane just starts to wrinkle, I give them a light watering.

I imagine every hybrid is different. I have one where I’m growing the parent outside and the keikis inside in a sunny east window. Both have bloomed well. The parent growing outside does fine with winter lows in the low 40s to high 30s, I bring it in as a precaution on nights with predicted lows in the mid 30s or below. The windowsill keikis probably don’t see temperatures below the mid 60s.

Last year I was lazy and left the outdoor ones to get rained on in the winter. This was great for vegetative growth but I got almost no flowers. I’m planning to cut back on water in November this year. I stopped fertilizing in September but October has been really hot and they get a lot of sun so I haven’t felt comfortable cutting back too much on water yet.