Winter Greenhouse for Cool Growers - Questions

[Clawhammer]

Here in 8b I grow a lot of tender outside plants that I overwinter in my garage. I have a large grow light for those that need light and less lit space for those that go dormant. I keep gardenias, cestrum nocturnum, tender rhododendrons, geraniums, Angel Trumpets, sambacs, etc in here with great success.

I have a heater set to come on @ 41 F

Last year I began using this room for orchids that like cool winters.. Cymbidiums, Aussie Dendrobiums, Nobile Dendrobiums.

Being the second year I am doing this, I used this setup to stock up on new plants. I have an idea of what I am doing but I never regretted asking folks here for any advice y'all may have.

Specifically, I'm planning on watering all about once every ten days with plain water (no ferts). Any concerns?

Any difference in winter treatment for Chinese cymbidiums (ensifolium, sinense, goeringii) from standard cymbs?

Any other types of orchids that require this cold treatment (41 F)? Just want to make sure I don't have anything else in collection that should be in the garage (or something else cool that I can buy haha).

Cheers!

[Roberta]

I don't grow much in the way of Chinese Cyms... my "standard" Cyms of course get the usual cold treatment. I don't dry them out... water less than in summer but not by a lot. Of the Chinese Cyms, it depends on which ones. Cym. sinense and Cym. ensifolium grow on the warm side - should probably stay with the general population. Others can go cooler. Cym kanran and goeringii can and probably should go to the cool side. But again, these don't want to dry out. Lightening up on the Cym fertilizer may help blooming... I use time release in spring that is pretty much pooped out by fall so it happens
naturally. Pleurothallids in general will love the cool. But need to stay damp and lightly fertilized.

[Fairorchids]

Aussie dendrobiums & nobile types have two rigid requirements:

A. Stop fertilizing after Sept 15th.
B. Reduce watering 90% after Oct 15th.

For both (growing in smallish clay pots with spaghnum), I go from 2-3 times a week to once every 3-4 weeks.

Once you see buds forming, you can start to increase watering again. Once flowers start to open, you can fertilize again.

[Roberta]

A note of caution with regard to severely reducing water for those Dens... this works in a greenhouse because there is consistently relatively high humidity. As an outdoor grower in a dry climate, I learned the hard way that one has to be more moderate in withholding water. In my case, the chilly nights seem to make up for the fact that the plants get watered (less, but pretty much with everything else) . So choose the "trigger" that works for you, "dry" or "cold" both seem to inspire flowers in the spring.

[Ray]

It seems to me that “winter rest” is more about reducing nitrogen than it is about reducing watering, which is why folks can grow them in S/H culture by just eliminating fertilizer from their winter irrigation.

[Capt.Meredith]

Thank you for all the great information. My Name is Meredith and I am new to this board. I am originally from Key Largo Florida and now live in Nairn Louisiana ( South Louisiana ). The winter months have been a challange for me and my Orchids. Thank you again

[Dusty Ol' Man]

Originally Posted by Capt.Meredith

Thank you for all the great information. My Name is Meredith and I am new to this board. I am originally from Key Largo Florida and now live in Nairn Louisiana ( South Louisiana ). The winter months have been a challange for me and my Orchids. Thank you again

Nairn? As in Empire?? That's practically the end of the world! Welcome from Lake Charles.

[stonedragonfarms]

I have a similar collection to what you are growing [about 25% D. speciosum & Aussie Native Den. hybrids, 25% Jensoa Section/Section hybrids, 25% mounted temp-tolerant species [ie L. anceps, D. moniliforme, etc.] & the remainder a mix of temperate terrestrials]
I don't withhold water to any of my Cymbidiums over the winter months, though the species in Jensoa all have 'stricter' watering routines in the winter months than do their hybrids--the warmer growers [ie sinense & ensifolium], when grown in the cold/alpine house, will need to be watered at the pot level only [ie don't overhead water them during winter...ever--you're apt to rot out the bulbs via water caught between the base of the leaf and the pseudobulbs] and only about 1-2x per month. goeringii, kanran & tortisepalum are more forgiving [generally] of overhead watering, as they all grow in colder [and wetter] winter conditions over their natural range; even so, generally reduce watering on them until you begin to see floral spikes elongate [usually late January-late February], then water every 5 days or so--remember, many of them are covered by snow during this part of the winter, so they are getting only intermittent watering.
Aussie Dens I don't typically water after the end of October, with a couple exceptions: 1. D. falcorostrum pushes its 'big' growth flush in the colder winter months, so it gets thoroughly watered about once a week--this is another one where it's imperative to not get water in the growths before they fully mature [they'll rot out otherwise] 2. On the rare sunny day, when the greenhouse is in the 70s or thereabouts, I mist all mounts and hanging pots--pretty much everything gets water then [though airflow out of the greenhouse is increased as well...] 3. Once I see buds on pretty much any of my Aussies, I will provide water to the plant 1-2x a week
A lot of it boils down to knowing the 'actual' conditions in your space--ie what is your rh on a given night at a given temp vs. on a given day at a given temp; how are your plants grown [ie inorganic media in glazed clay/plastic is vastly different than bark and terracotta], what is your air exchange rate, etc.
Follow-up question: You run with 41f on the low end; what are average day temps in your greenhouse over the winter?

[Clawhammer]

Stonedragonfarms: So much good info, thank you, I am setting my watering notifications on my calendar based on this advice.

Thanks for mentioning anceps. I have a big one in my indoor growroom that I will move out to the cold greenhouse and I will grow it outside next year. **Any other cattleya that can take 41 degrees?** I'd like to move as much outside as possible.

Here is my tracker from Dec/Jan last year... The temp gradient is 5-7 degrees. I have a heater to set the floor at 41, I was thinking of using it to raise the daytime temp a little higher than the light alone. I have a fan on the plants 24/7

[IMG]Untitled by Eric, on Flickr[/IMG]

[Roberta]

L. (C.) purpurata, C percivaliana, C. tigrina (leopoldii), C. labiata, C warnerii, C. bicolor. C. mossiae, C. triananae, highland form of C. maxima, C intermedia, C schroederae. I have forgotten some I am sure, take a look at my website Index of Plants to see what I grow outside. In fact, the list of "big Catt" species that need to be warm is shorter than the list that can tolerate cold. (dowiana, lueddemanniana definitely need warmer,I don't grow them because I don't have room in the GH)

Disclaimer... don't know how this translates to higher latitudes... my outdoor plants get cold nights, but days warm up and have a bit better light duration than farther north.

(Just a note... last night's low was 46 deg F in my back yard, but it'll get somewhere between 65 and 68 deg F. this afternoon. Fairly typical for what passes for winter at my house... we'll get into the low 40's F and occasionally even mid 30's as winter progress but days usually get into the 60's F )