# Potting method for Cypripediums in a hot climate



## KyushuCalanthe (Jan 25, 2014)

A tutorial vid focusing on using the "double pot method" (AKA "pot in pot cooler method") to grow Cyps. Most Cyps are native to cool to cold temperate regions and require root temperatures below ~ 25 C (77 F) to remain viable. In this video you'll see how I push their tolerance to even warmer areas - right up to nearly the subtropics of southern Japan, a climate similar to say Charleston, South Carolina. Not a barn burner, but informative (I hope!).

The pot in pot cooler

And the companion article is here.


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## SlipperFan (Jan 25, 2014)

Clever!


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## monocotman (Jan 26, 2014)

*potting cyps*

Tom,

great video!
Do you repot every plant every year?
It is amazing to see decent increase in a species when the summer weather is so hot.
I know that the conventional wisdom is that cyps do not enjoy temperatures over 25 degrees but it is apparent that with care they can do well.
We had a decent summer in the UK in 2013, the best for several years with plenty of days over 25 degrees.
Most of my plants did not suffer at all as they were kept out of the sun completely and watered every day.The couple of plants that received morning sun (reginae and reginae alba) showed stress with some leaf tissue loss.
So another question - did you keep these plants in the shade all summer?

Regards,

David


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## Linus_Cello (Jan 26, 2014)

Thanks!

Can you tell us more about:
There are less strenuous variations on this method, for instance placing a plastic pot inside a larger clay pot with sphagnum moss filling the void between the plastic and clay pots. This not only keeps the inner pot cooler, it also adds to the humidity level near the plants.

Do you use the wicking tape with the plastic pots? What is the disadvantage of using a plastic pot rather than the clay pot?
I've been using clay pots to help with evaporative cooling. But the disadvantage with clay is that it can crack and break, especially after the winter.

Also, what do you do in the winter for these cyps?


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## eteson (Jan 26, 2014)

I think your method could work for phrags also. Let's try it...


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## KyushuCalanthe (Jan 26, 2014)

*LONG response (sorry)*

Gosh folks, I could write a book about this. This technique is offered as a relatively simple, low-tech, and yet effect method to keep pots cool enough to grow Cyps where you have no business trying to do so. I'm sure lots of other plants could be grown this way.

David,

Yes, I repot every winter when the plants are in full dormancy. It is necessary in this climate since older roots are stressed badly and tend to die quicker than they should. Under cooler conditions this is OK since the dying tissues will simply compost into the growing medium. In the heat here they tend to simply harbor disease - bacteria and fungi - and have to be removed.

The plants are in the shade all summer, but very bright shade, under azaleas and tucking amongst ferns. I have no choice but to keep the plants out of the sun and away from concrete structures (they radiate heat throughout the night and tend to dry the air). When I first starting trying this technique the plants were grown in more controlled conditions - under a covered porch with a fan blowing on the pots to increase evaporation. The plants did OK, but suffered once the true heat of summer hit in August. So I put them under the shrubs the next year and they did much better.

Linus,

Indeed there are less difficult ways of doing this idea, and more strenuous too. I've used the sphagnum method to grow seedlings of C. macranthos in a plastic pot for a few seasons and it seemed to work OK. Humidity isn't usually a problem here (averaging above 70% most of the time), however near hot walls sphagnum works wonders for small plants.

The purpose of the two clay pots is to get the inner pot to wick water outwards, thus cooling the medium. Plastic of course doesn't allow this. In a true "zeer refrigerator" set up there would be moist sand between the inner and outer pot, increasing the evaporation much more. I started to try this technique as well, but honestly ran out of patience since it required maintaining water constantly in the outer pot, made it a pain to water the plant, etc., so I gave up. I can't say that a plastic pot would be worse or better, though it would probably cause problems during heavy rains, since pots could remain truly water logged. The summer monsoon in Japan is intense.


This year I may try putting sphagnum between the inner and outer pots to get even more wicking power from the inner to the outer pot surface. The idea is to maximize circulation of water through the system, and the added sphagnum might just do that. That will require a slightly larger outer pot for the sphagnum, and longer tape at the base to reach the water reservoir. The Cryptomoss also is a wicking material, hence it as well is important to make this system work - typical composts probably would be less effective. 

A note about summer time temps here - they are blistering, averaging 30-34 C (86-93 F) daily without a break and only going down to 25 C (77 F) at night from mid July through September. In the worst of the heat (late July through mid August) air temperatures don't fall below 27-28 C (80 F+) ever, and day time highs are commonly 35 C (95 F) or more. Now you can see why I have to find a way to keep these poor plants from cooking to death!

Note about winter temperatures here - using the USDA cold hardiness zone scale I live in zone 9b, but in truth winters here are more in line with Atlanta, Georgia rather than Daytona Beach, Florida. The reason is we don't get the extreme cold events of Atlanta, however the average temperatures are in line with more northernly climates. So winters here are just barely cold enough to vernalize Cyps. For that reason I leave them out all winter in the shade.


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## monocotman (Jan 27, 2014)

*repotting cyps*

Tom,

repotting every year seems such a laborious task - you must really enjoy growing your plants.
Growing them under shrubs with the increase in RH and reduction in wind sounds like a good idea.
I did the same in the UK one year when there was nowhere else to grow them and they did fine.
If you can increase species with this system have you had any success with hybrids?
The fact that the old roots die fairly quickly in these conditions must be one of the biggest differences between culture in the UK and Japan.
I see few dead roots when I repot plants, even those several years old.
This is especially so in hybrids. Some roots must be at least 5 years old.

On another note we are having a bit of a non winter here in the UK with lots of wind, rain, floods etc but precious little frost and sub zero temperatures.
A 9 bud plant of cyp formosanum has decided to send up a single growth to about an inch above the compost. It seems to have stopped growing for the moment - I'm not sure what I'd do if it starts to extend,

Regards,

David


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## KyushuCalanthe (Jan 27, 2014)

David,

Madness drives me on... 

The only hybrids I've tried so far have been Aki, Gisela, Philipp, Sabine, Lothar Pinkepank, Victoria, and Michael. Most of those were put in the outdoor bed and a couple years back suffered badly by a wave of leaf rot that took all of them to the ground by early June. Some recovered, but have struggled to regain strength. Only Aki, Gisela and Philipp have provided repeat flowering.

Time and effort willing, I'm going to take the remaining plants out of the bed and pot them up and see if they do better this year. C. japonicum and C. formosanum can grow in outdoor beds here, the latter being the most heat resistant Cyp I've ever grown. Your formosanum should be OK if you can keep it frost free. These can be in growth much longer than most Cyps - from February to December won't kill them. Mine begin growth in late March, flower by mid April, and go down sometime in mid November.

Strange warm weather coming here this week too with forecast highs in the high teens, but nights remaining below 10 C. Odd weather to be sure. Thankfully no flooding!


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## JPMC (Jan 27, 2014)

Tom, thank you for the information. Recently, after a disaster with disas I think that I have a viable variation on this theme. I read online that a grower in Tennessee was able to grow disas using an old freezer chest with the lid removed and a constant circulation of cold water produced by the freezer. Since I am in an apartment, I cannot do as elaborate a job as he I scaled it down to removing the lid of the chest and replacing it with a copper insert that covered the whole top of the chest but was 1 foot deep into the cool part of the chest. The disas withered in the 90F summer temps. so I was about to throw the freezer out but before I did I tried some of my cypripediums in it and they seemed much more vigorous. I have yet to see the results this spring, but I'm hopeful. For example, my segawai which had only one growth for the last few years has two visible buds just below the surface of the growing medium when it went into dormancy last fall. I think that like your method, this one keeps the roots cool while the leaves are subjected to summer temps. It seems that the cypripediums are not as wimpy as the disas I tried.


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## KyushuCalanthe (Jan 29, 2014)

Hey JMPC,

That's funny that you tried that technique. I remember having similar thoughts. A Warden case is another option, and would probabaly work for Disas. Without a doubt Cyps like cooler roots (below 20 C is optimal for most, and necessary for the true northern species). 

The double pot method is offered as an easy to use, relatively cheap way of growing Cyps al fresco with little intervention, except fertilizing. I have to admit though its longterm viability is questionable without using some kind of fungicide to keep nasties at bay. If I had a larger collection I'd try keeping plants in the same pot for more than one season, but not with out a periodic fungicide bath. My babies are just too precious to me and so I've not had the gumption to try this out yet.


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## Ray (Jan 30, 2014)

Another alternative is the use of an unglazed clay pot for semi-hydro culture. The evaporation from the medium alone will do some cooling, and if you add the pot sidewalls to that, it's pretty significant.


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## Stone (Feb 11, 2014)

Here's another variation on a theme. 2 clay pots with sphag in between. The outer pot sits in a saucer and keeps the moss wet. The inner sits on the moss but is below the water level. The saucer is not particularly important as the moss is very easy to re-wet by pouring water between the 2 pots. However I have found that it dries out very slowly. The outer pot is always moist and cold to the touch even on hot days but I've had to keep them in the greenhouse with a fan on them as the weather outside is way to dry and hot at the moment. Still feeling my way with these things


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## Dido (Feb 11, 2014)

Stone it is not good to use bark in cyp mixes, I had very often problems with that. Dont remove it now. 
It look like the formosanum need soem help in opening. 
the calceolus looks great, but no flower if I see right....


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## Stone (Feb 11, 2014)

Dido said:


> Stone it is not good to use bark in cyp mixes, I had very often problems with that. Dont remove it now.
> It look like the formosanum need soem help in opening.
> the calceolus looks great, but no flower if I see right....



There is not too much bark in the mix and it is old (composted) and washed. The rest is gravel, diatomite (mostly) and a little hard treefern. I did not really expect a flower on the calceolus - it looks a bit weak to me. The formosanum is opening up ok now. The hot weather is a problem!


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## Dido (Feb 11, 2014)

Calceolus looks fien, this is normal. Maybe add a little lime to it, as she likes it. This type will not get higher....


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## cnycharles (Feb 11, 2014)

When you were describing the two pot method, did you mean to say the inner pot sat above the water level (instead of below which would soak the inner pot)?


Sent from my iPhone using Tapatalk


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## monocotman (Feb 11, 2014)

*cyp culture*

Mike,
your system looks to be working great at the moment but must be 'high risk'.
What is the temperature in the greenhouse?
I'd be inclined to put the pot on the floor in the coolest part of the house.
I find that the easiest way to kill a cyp is to heat stress it so I do hope that the water reservoir does not run out!
If it does, the plant will turn to a crisp in about a hour.
Good luck!
David


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## KyushuCalanthe (Feb 11, 2014)

Mike, I've used a similar set up growing seedling Cyps with mixed results since seedlings can't take too much abuse! Do you use any wicking tape, or just top water the pot?

Charles, I've found that the inner pot can be in the water a bit and there is no problem. 

The real trick is to keep water cycling through the system continuously - not easy with such a low tech approach, but good enough to keep things a bit cooler at least.


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## Stone (Feb 11, 2014)

Dido said:


> Calceolus looks fien, this is normal. Maybe add a little lime to it, as she likes it. This type will not get higher....



I put a little lime in.


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## Stone (Feb 11, 2014)

cnycharles said:


> When you were describing the two pot method, did you mean to say the inner pot sat above the water level (instead of below which would soak the inner pot)?
> 
> 
> Sent from my iPhone using Tapatalk



Yes that's what I meant


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## Stone (Feb 11, 2014)

monocotman said:


> Mike,
> your system looks to be working great at the moment but must be 'high risk'.
> What is the temperature in the greenhouse?
> I'd be inclined to put the pot on the floor in the coolest part of the house.
> ...



The temps lately go from 15C to 35C. Its the coolest spot I can find without keeping it in darkness. The water reservoir has dried up for hours but like I said It didn't make much difference. The moss holds about 1/2 a litre of water by itself and this seems to slowly seep into the inner pot as well as to the outside wall.


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## Stone (Feb 11, 2014)

KyushuCalanthe said:


> > Mike, I've used a similar set up growing seedling Cyps with mixed results since seedlings can't take too much abuse! Do you use any wicking tape, or just top water the pot?
> 
> 
> Tom, No wicking tape. I've just been removing the inner pot and watering that before replacing it in the moss but not because it really needs watering, just because I feel I need to  How much water do they need? They don't really seem to dry out at the moment. ( or very slowly anyway ) A lot of the dish water ends up in the plant pot. Do they like a good flushing with water from above or do they prefer bottom watering. Also, when do roots emerge from the new growths?
> Does your method keep the outer pot damp/wet?


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## KyushuCalanthe (Feb 12, 2014)

Stone said:


> Tom, No wicking tape. I've just been removing the inner pot and watering that before replacing it in the moss but not because it really needs watering, just because I feel I need to  How much water do they need?



Cyps need continuously moist conditions year round. True drying at any time is dangerous, hence David's comments. Most are associated with forest cover of some type so humidities are usually high while in growth.



Stone said:


> They don't really seem to dry out at the moment. ( or very slowly anyway ) A lot of the dish water ends up in the plant pot. Do they like a good flushing with water from above or do they prefer bottom watering. Does your method keep the outer pot damp/wet?



As long as the water in the bottom reservoir is clean, that should be OK. Cyps in general hate wet/soggy conditions despite some being found in wet environments (which doesn't need to be replicated in cultivation). With Cyps it is best to make sure the medium remains clean and well aerated, as with any slipper orchid. Using my method the outer pot never is damp. My plants spend their summers under shrubs where they get frequent rain, and so the pots get flushed often. 

On hot, dry days the wicking tape does the job of keeping the medium moist, and hopefully cooler - assuming I don't forget to keep the reservoir full! The growing medium I use is designed to wick water as well which increases evaporation. I think this is key in making this particular system to work efficiently. I don't know how or if it would work with other substrates.



Stone said:


> Also, when do roots emerge from the new growths?



Once the new growth bud is forming and enlarging (around mid summer) they should be growing new roots. Those can continue to grow on into the fall. A new growth bud that has no new roots, or highly shortened ones, indicates a stressed plant.


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## Stone (Feb 12, 2014)

KyushuCalanthe said:


> > Using my method the outer pot never is damp.
> 
> 
> You will get more efficient cooling if you can keep the outer pot wet. (and well ventilated) But this will not work well in very humid conditions.
> http://www.wikihow.com/Make-a-Pot-in-a-Pot-Refrigerator


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