Dormancy question - Deciduous dendrobiums

[cwcervantes]

Hello everyone!

I have a quick question for all the expert growers here:

When do deciduous Dendrobiums -- specifically nobile, primulinum, anosmum/superbum, parishii, & unicum -- lose their leaves and go dormant?

I've stopped watering for about two weeks now but there's no sign of leaf drop; roots, leaves, and even new canes continue to grow. I want to get some good blooms but I think I've done something wrong. My Den. unicum seems to have the beginnings of flower buds but the others nothing.

I believe Den. nobile can stay out up until freezing if dry, but the others need warmer temperatures?

Thank you all in advance for any advice and guidance! I am really fond of the blooms on these plants so I want to get it right.

Best regards,
Cody

[Anteater]

I have two nobile types and am not an expert, but I don't change anything with them. I grow them inside under lights in coconut husk mixed with perlite and charcoal. The thermostat is set at 69 degrees. We have low humidity. My anosmum starts shedding leaves at the same time it sends up a baby, and shortly after starts budding. It's budding now with half the leaves gone, and the others yellowing.

[coeruleo]

hmmm... i am no dendrobium expert by any means, in fact i am trying to sort them out myself. i only have a kingianum (second winter for us) and a recently acquired tetragonum. i think they are in a different division perhaps? i was under the impression that a 'deciduous' dendro only has its leaves for one growing season, but does not always mean that there is a period of completely leafless canes. newer growths will have leaves still. i could be wrong. i know the 2 i have keep their leaves more than one season, but apparently still have 'dormant' seasons in winter, but still have a lot of leaves, while older canes eventually drop their leaves (but may still produce blooms??). my kingianum i am letting go into winter rest now, a month later than last year, hoping to have it rest during my coldest weather as last year i was bringing it our of its winter rest just in time for 40degree nights. however, the tetragonum seems to be beginning flower spikes already. or something anyway. you have mentioned 2 or 3 on my wish list though (unicum!!!), so i am interested in what experienced growers of dendros can reveal in their experience. unicum is one that can supposedly take some winter lows, which is why it is next on my list, i mostly grow outdoors and my winter lows usually approach 39 or 40 degrees sometimes. if you like i can PM you a link to a site that used to focus on species that are able to handle socal outdoor weather year round. they have expanded to some warmer things in the last few years, but they profile a lot of orchids that are more hardy. i have been quite surprised at the amount of orchids i can grow outdoors in winter if kept dry enough.

[cwcervantes]

Hi, coeruleo:

Feel free to PM me with the link to that site. I too grow mostly outdoors so the site would be useful.

[stateless]

I've stopped watering my nobiles in Nov. they still have some leaves on them, but we've been warm so far this winter, and I never worry about the cold fronts with them they stay out when it's in the 30's at night.

[AtantaR]

I have a Den. perishii that didnt lose its leaves for a couple years. I grow indoors mostly...then i put it outside this past summer and they all fell off at the end of the growing season here. Maybe it got the jist from all the decidious trees around here..lol ....and i dont think it particularly matters if the leaves fall off or not. I believe they will still bloom either way. Just in nature i think they fall off with the ending of a season and "dormancy" of some sort

[catttan]

I don't grow the nobiles but the for the others the dry , cooler season begins from end of Nov to end of Feb and this should coincide with the shedding of leaves. Den anosmum is the exception as it is very adaptable, being found from the the true monsoonal regions at the foothills of the Himalayas to the hot, wet areas of the Equator with year round rainfall. Most of the deciduous dendrobiums mentioned can take short cool periods in the 30s and 40sF with no frost - indeed this short cool periods do actually stimulate these dendrobes to produce a more profuse show in the spring. In my place we don't have the lower temps needed and therefore don't have the impressive show that these dendrobes are capbale of.

[coeruleo]

sorry, i tried to send PM but it would not let me. i think you have to change a setting first?

[arwan]

I leave them outdoors all year round even when the temp goes down to 30-40 F. Some of them lose their leaves when temp starts to drop down but some retain their leaves. I stop watering and fertiliser altogether but sometimes i just give a few spray of water in the morning when they look too dry. And when spring comes when they starts budding i resume watering again. Hope this helps.
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[kspalding]

If you suddenly quit watering you are lucky if dormancy is all you encounter. When winter comes you need to gradually reduce the watering based on drop of temps. The way to determine if watering needs to be reduced comes in the fall. Usually around this time the canes will stop producing new growth. Then once new growth begins to appear (usually late winter/Early spring) increase the watering to usual. It is actually normal for these plants to drop alot (if not all) of their leaves during winter. Also, continue feeding the plant...just dilute the liquid fertilizer and count the water added to the solution as part of the watering. Don't ever just stop watering if the plant is not use to it. This can lead to much worse than a dormant plant.