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  #1  
Old 07-30-2020, 06:18 AM
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10 degree minimum
Default 10 degree minimum

I was told by a commercial orchid grower last week, no orchid will die at 10c/50f, I understand many won't thrive but I'm actually referring to dying overnight or within weeks.

I'm debating this statement, although everything else he's said has been right. Am I being too careful with minimum temperatures?

Compounding this, I visited a local grower who had a greenhouse that was 2c the prior night and had a 5ft Vanda in flower, Renanthera, Aerides, Rhyncostylis, Bulbo sanguineopunctatum, and dozens of Oncidiums growing in a 12c maximum day?
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Old 07-30-2020, 07:43 AM
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Orchid cultural conditions are intertwined, so discussing any single factor in isolation is meaningless. At nominal 'far too low' temperatures, plants that are dry will live, and plants that are soaking wet will die.

I aim for min 55F (12.8C) in my greenhouse, and occasionally it drops lower (I have seen temps down to about 8C on my High/Low thermometer). I can grow almost anything in that greenhouse, except distinctly warm growing plants (such as Cattleya dowiana and it's direct descendants). Likewise, I would not attempt Vanda sanderiana, but all my Vanda hybrids are doing just fine.
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Old 07-30-2020, 08:58 AM
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Thanks, my query was assuming all other elements being optimal outside the 10c temperature if the warmer growers would still stay alive, at least long enough for Spring.

I'd understand better if the decline of plants in cooler weather was more due to the transition from warm to cold climates (purchasing plants from interstate), rather than their genetic cold tolerance.

I have the thermostat set between 10-12 but only water once a fortnight for risk of rotting plants, I'd imagine they're dehydrated, but alive.
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Old 07-30-2020, 09:30 AM
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Quote:
Originally Posted by Fredmax View Post
I was told by a commercial orchid grower last week, no orchid will die at 10c/50f, I understand many won't thrive but I'm actually referring to dying overnight or within weeks.
Fred --- dying overnight is pretty serious stuff. Is this happening to some of your plants?

We've been getting those sorts of temperatures way up north here - north queensland - such as 10C - and all my orchids have no problems. I have some outdoor full-sun ones, and the bulk of my orchids are semi-outdoors ones - growing under a balcony.

The bulk of my orchids grow in quincan gravel (aka scoria, lava rock). I usually water each day, which also allows me to watch all the orchids like a hawk.

If you do have issues with temperature ----- then consider media type, and whether the roots stay cold plus wet for relatively long periods of time, and consider whether the leaves remain wet for long periods of time, and how much air-movement is in the growing area.

And also consider what max temperature you get in the green-house.
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Old 07-30-2020, 10:27 AM
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Actually it's just a general question for my better understanding of the thresholds the plants can tolerate.
I had a bad run with fungus but everything in the greenhouse is actually doing well at the 10c minimum, so I'm considering moving more plants back in there. No overnight deaths, although I have a Vanda Teres from Burleigh Park Orchids which in 2 nights of 10c looks like it's been in a fight, all purple and yellow - this is a plant according to Andy's tolerates 7c/45f.

I had always assumed anything below 15c regularly (over 12 weeks) was terminal as the equatorial species rarely get below that natively.

Last edited by Fredmax; 07-30-2020 at 10:30 AM..
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Old 07-30-2020, 03:36 PM
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I had always assumed anything below 15c regularly (over 12 weeks) was terminal as the equatorial species rarely get below that natively.
Fred - I have read that some plants require temperature to be in certain ranges for carrying out certain functions - biological and/or chemical stuff needed for cell development, and food making, energy or whatever important processes there are for the orchid to grow or stay healthy.

Eg. if the temperature stays relatively cold for weeks, or is on average relatively cold for weeks, then some orchids that require say tropical conditions and temperature might not be able to handle it.

Also, if some plants require temperature at certain times of the day to be roughly 'above' a certain value for supporting some important processes, and to later be below that temperature for something else (eg. resting) ----- then some plants could have issues if the conditions aren't 'provided'.

Also - there are details found about temperature change and rate of change. If temperature changes from one temperature to another relatively quickly, and if the initial and final temperature difference is large ...... then cells can develop problems, like dying. Sometimes, warm leaves getting chilled very quickly somehow (or the reverse) ...... can get bruising or cell collapse. This can also be 'promoted' by abruptly putting cold water on warm leaves. Or spraying alcohol on warm leaves - where cooling effect chills the leaves (under some conditions) ----- could probably cause some health issues.

And in a green-house, if it's humid and moist, and if there's no air-movement to suppress or eliminate certain unwanted fungal/bacterial activity (eg. by moving air over leaves and stem, and over roots and through potting media), then issues can occur that way.

So various considerations should be made about the growing area and environment and the growing/watering/fertilising/mag-cal/potting/potting-media etc methods.

Once these aspects are listed ----- then we have to look at each one, to see if issues could exist. And if one or some exists ------ need to see if we can do something to address it, to remove the issue(s).

I'm not a collector of a huge number of orchids, but have enough tropical type orchids grown for relatively long periods of time - a few decades. And a few decades ago, I wasn't able to keep alive 4 orchids. I initially thought it was 3, but actually 4 - and can even remember them. An L. anceps. C. bowringiana, Blc. Memoria Crispin Rosales, C. skinneri. They were the first lot of orchids that I grew. They didn't make it because I was a newbie and didn't know how to care for them.

But - interestingly - thereafter, I've never had any orchid die in my care. This has been due to - in a large part the fantastic tropical growing conditions here (temperature, air-movement in my growing area, lighting levels etc) ----- and surprisingly not much 'pest' activity in my growing areas. Or if there is ---- there hadn't been much or any nasty pest activity that I had to really deal with, except spider mites on paphs and catasetum.

The other aspects behind the health of the orchids is what was described before - making sure to avoid doing things to the orchid (or parts of orchids) that can lead to a down-turn in their health. So basically - lots of reading about what can cause orchid health issues, and how to cut down or eliminate issues.

It's true that there are always uncertainties --- things sometimes beyond our control -- like encountering virus (which I've never had issues or seen the results of - due to luck most likely), or just something.

I did have something concerning happening to my entire batch of catasetum last year, where the whole lot of them began to have sections of their leaves rot in sections in or around the 'crown' region. Something basically got on the whole lot of those catasetum type plants --- 20 or more of them. Application of a fungicide/bactericide sorted out that situation. That was concerning actually, but panned out well in the end.

I think it all came along after a spider-mite attack. Possibly soap spray solution got the leaves wet for too long (within the crown region) and some nasties just started to destroy the leaves around the crown region - rotting. Interestingly, the treatment was massively effective (with yates anti-rot phosacid) - which just so-happened to work. Amazing turn-around on every one of the catasetum-type plants.

I did have issues once with two juvenile paphs, with leaves unexpectedly getting rust coloured spot (small to begin with - on old and new leaves!), which spread - leading to rot. And also very interestingly - copper spray sorted it out amazingly - when other stuff (thiomyl, yates anti-rot appeared to be ineffective).

The leaves had not even been wet! So this is what I mean about some uncertainty.

But having some goodies on-hand if we need it --- treatments --- can be handy for sure.

I did recently see for the first time, a dendrobium beetle larva attacking one of my mini-catts! Possibly brought about by cymbidiums nearby with the long lasting flowers - may have attracted up those beetles.

So watching the orchids like a hawk each day can definitely help cut down on certain problems, or gives time for us to respond to situations.


Last edited by SouthPark; 07-30-2020 at 09:35 PM..
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Old 07-30-2020, 09:57 PM
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Fred,

Don't get hung up on geography. You need to know at what elevation the plants grow. For example, Vanda tricolor from Indonesia, which is close to equator, grows at 4500' elevation, so it does fine with generic Cattleya conditions (& temps down to 10C or below).

Noticed you comment about watering only every 2 weeks. Irrespective of what you use for potting mix, that does not make for well grown orchids!
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Old 07-31-2020, 12:19 AM
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How warm it gets the next day makes a huge difference in what plants can tolerate. If it's 10C / 50 F at night and 12 C / 53F the next day, for weeks on end, a lot of orchids will die that would survive 10C at night and 25C / 77 F the next day.
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Old 07-31-2020, 02:43 PM
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A thought if you occasionally get a cold winter night... a dry orchid will tolerate more cold than a wet one. So water in the morning (giving them all day to dry out) and skip it if the forecast is for particularly cold. But I can't think of anything that would be happy with every 2 weeks, except for those that go dormant in the winter and want little water at all.

I totally agree with FairOrchids with regard to geography... elevation is also an important piece of the puzzle. I live in a frost-free area (coastal southern California, USA) and grow lots of orchids from equatorial regions outdoors in my yard (I mostly grow species) - For equatorial orchids I have found that those that come from elevations above around 1200 m, do fine through winters that get fairly close to freezing. At higher latitudes, lower elevations have the same effect. But even when nights are cold, days typically are warmer. Winter daytime highs below 18 deg C are pretty rare
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Old 08-03-2020, 09:27 AM
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Thanks for the advice, yes you're right I'm probably not factoring the subsequent day time temperatures. Sadly with the fortnightly watering, I'd rather have a plant with a period of dehydration than the overnight rot I encounter, especially on plants in sphagnum as media, I find media just doesn't dry when days are 12 and nights are 3c, quite often I have to squeeze the waterlogged roots or find black fungus within a few days when I notice they're still wet.

This will change when the temps go back to the 30c - 40c we get in Summer and need multi waterings every day. Elevation is my judgement on if I should buy the plant, I try and avoid any plant that is below 800m habitat, the fear in some cases (Mediocalcar and Ceratostylis) is that the heat will wreak havoc with the cooler tolerant plants.

I must've had a mental blank when I made this post, I can safely say Aganesia, Phalanthe Den's, Spathoglottis, Gramatophyllum and even supermarket Phal's haven't tolerated 10c even with a couple of season's to acclimatize, and promptly tell me so with yellow leaf drop.

I had hope for Cattleya's but around 50% of them have very purple leaves and are now indoors until September, I haven't been able to determine which Catt's can deal with cold and which don't.

Oh how nice it would be to live in the tropics and not be restricted to Cymbidiums.

Last edited by Fredmax; 08-03-2020 at 09:33 AM..
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