Cold treating Den Nobile hybrid

[SteveM]

Hey all,

I have 2 den nobile hybrids out in my unheated greenhouse. Right now the temp outside at night is whats inside. Not insulated very well, old 4mm poly carbonate panels, but it does not get any condensation or frost inside and is sheltered from any wind, other than a small fan on very low just to circulate air. I know others have worried about subjecting them to too much cold. Anyways the past 2 nights we got down to 38, days rebound to the low 80's inside greenhouse. They both look good with the exception of 1. One of the oldest leaves is turning yellow down the middle vein. Anyways Its going to warm up slightly and make it back in the mid to low 50's at night in a few days. Tonight should be 42ish. its pretty dry in there, I did have to water them both today, I watered very lightly. So I will probably take 1 in tonight and see how the other one does. How low has anyone gone with nobiles. I do know that it will take a few days before they respond to cold damage. also which one would take the colder temps better after watering one in lava rocks or one in fine ochieata bark. I am also worried about the large temp differential. Also if I bring them in for a day or 2 and they will be warmer than 68, will that throw off the cold treatment.

[estación seca]

Different hybrids tolerate different lows. I'd be nervous about 38 F / 3C unless I knew those plants could take that. Six weeks of night temperatures below 55 F / 13C is the recommendation. I suspect a few nights at 68 F / 20C might interrupt flowering. Do you have a colder part of your house? Could you shut the heat register to an unused room overnight?

[BON]

I have had (many = dozens) Den. nobile hybrids have night temperatures of 34 F with no problems. If they are dry they are fine at night temperatures in mid to upper 30’s. Yiro Yamamoto wrote they can survive as low as 32 F, but I am personally not comfortable with them lower than mid to upper 30’s if I can help it. Flower bud formation is triggered by plants getting night temperatures at or below 56 F for about a month. Yellowing of leaves on older canes is normal and when grown with cold Fall temperatures the older canes are deciduous. When blooming flowers last longer in cooler temperatures and 50’s is ideal for flower longevity.

[BON]

Also wanted to add that a Den. nobile’s ability to handle temperatures in the mid to upper thirties is based upon the growth being mature and hardened off. I sometimes get some late new growths on some hybrids that is very young and tender at this time of year, and new, soft growth is not as tolerant of cold and could be damaged at temperatures of forty or below. Also, as pointed out above it can be helpful to know the parentage of hybrids as the new generation of nobile hybrids has some varieties that don’t require cold treatment to initiate flower buds. Even so those will tolerate cool Fall/Winers quite well. And if you don’t like the look of bare canes, cooler temperatures along with keeping the plants moist/watered enough will allow for bud development on mature canes that will retain their leaves while blooming.

[SteveM]

Thanks ES and Bon. I decided to take them in just to be safe. As with the keeping dry I did just water them and didn't want to chance it. I will probably bring them out tomorrow night. ES I have not had my heat on yet, I know its been 38 outside and house is still around 70. I could open a window I suppose but then I probably will need to turn the heat on LOL. And Bon, yes one growth is about half grown, on one and about 2/3 on the other. I did notice a few stubs adjacent from where the leaf meets stem, I only see 2 but yes I think they may be buds. It has been in the 60's at night for almost 2 months, in the low 50's for about 2 weeks. Just recently we skipped the 40's and went directly into the 30's LOL...I also looked at there location climatic data, Most of the locations although they are very broadly distributed have lows around 20 degrees F . The weather seems to be very comparative to what we have right now here in TN. But I do not plan on keeping them out that cold.

I panicked with my zygos and took them in a few days ago. Cymbidium although it is Golden Elf, is loving these cooler temps and still in GH. New growth has started to take off and keeps producing more off shoot growths, Just hasn't developed new bulbs yet.

[Roberta]

Cym. Golden Elf has very small p-bulbs, you almost can't see them unless you dig around in the medium. Never fear, it's growing. It should be fine into the low 30's F. (The Cym. ensifolium parent gives it the slim-leaf form and late summer blooming, the other parent is standard type that gives it the usual Cym cold-tolerance)

[SteveM]

Thanks Roberta,

It didn't bloom this year. Last year I got it in July and went into bloom in September. last fall I had a problem getting the medium/moisture right and had some new growth (like 4) rot away on me. Thought it may have been fusarium due to the nature of the rotting, but all is good now anyways. Luckily this spring and summer I was able to get 3 solid growths that are still growing along with the newest growths which I have not yet counted but are a good amount.

[Kittyfrex]

Never had issues growing them close to 0C, with even some dips. The one time i had buds was when i first let them overwinter outside in the sun. I don't think that's too much to worry about, especially if they are in the sun. And mostly on the dry side.

[SteveM]

Thanks Kitty,
They are getting a good amount of sun. I just took down shade cloth a few weeks ago. Id say about 5 hrs atleast of full sun. The light is pretty well dispersed, today was around 90 in there. Thats my main worry is the 40 to 50 degree difference. They seem to be doing well. I even took the zygos back out there since temps are going to be at low around 50, They are in a more shadier spot.