Paph Sanderianum Culture?

[The Orchid Boy]

I got my sanderianum today and my free Paph. gratrixianum seedling.
There has been a discussion on Slippertalk about Paph. sanderianum culture, and a lot of people have reccomended higher humidity for me. What kind of humidity do you all grow your sanderianums in? Some say high humidity not just for blooming but for the overall health and longetivity of the plant. The thread can be found here: Fertlizing and watering Paph. sanderianum - Slippertalk Orchid Forum- The best slipper orchid forum for paph, phrag and other lady slipper orchid discussion!

[naoki]

Orchid Boy, maintaining high humidity is beneficial for many orchids. Here is the (simplified) reason.

During the photosynthesis, H2O get broken down, and O2 is generated as the byproduct. The problem is that an important enzyme for photosynthesis (rubisco) can bind O2 or CO2. Carbon gets fixed if it binds to CO2 (good thing for plant growth). However, if the concentration of O2 is high in the leaf, rubisco binds to O2 and produces an useless product. Subsequently, to convert the useless product to more useful product, plants have to spend a lot of energy, and also it will lose a carbon (bad thing for plant growth). This problematic reaction is called photo respiration. In order to reduce the O2 concentration in the leave, plants need to open stomata. But if the relative humidity is low, the plant leaves loose too much moisture, so they have to close the stomata (therefore, carbon fixation rate goes lower due to photo respiration). Plants which has adapted to humid environments grow slower if you can't maintain high humidity.

Most orchids can tolerate lower/moderate humidity, but they may not be growing at the optimal speed.

I try to target 70-80%RH in the grow tent (mostly species Phals and Paphs, including P. sanderianum), but it could dip down to 60% during the day time. As a side note, for Phals, night time humidity is most relevant (they are CAM plants which open stomata at night).

[Susie11]

Originally Posted by naoki

Orchid Boy, maintaining high humidity is beneficial for many orchids. Here is the (simplified) reason.

During the photosynthesis, H2O get broken down, and O2 is generated as the byproduct. The problem is that an important enzyme for photosynthesis (rubisco) can bind O2 or CO2. Carbon gets fixed if it binds to CO2 (good thing for plant growth). However, if the concentration of O2 is high in the leaf, rubisco binds to O2 and produces an useless product. Subsequently, to convert the useless product to more useful product, plants have to spend a lot of energy, and also it will lose a carbon (bad thing for plant growth). This problematic reaction is called photo respiration. In order to reduce the O2 concentration in the leave, plants need to open stomata. But if the relative humidity is low, the plant leaves loose too much moisture, so they have to close the stomata (therefore, carbon fixation rate goes lower due to photo respiration). Plants which has adapted to humid environments grow slower if you can't maintain high humidity.

Most orchids can tolerate lower/moderate humidity, but they may not be growing at the optimal speed.

I try to target 70-80%RH in the grow tent (mostly species Phals and Paphs, including P. sanderianum), but it could dip down to 60% during the day time. As a side note, for Phals, night time humidity is most relevant (they are CAM plants which open stomata at night).

^^Simplified???

I get the basic drift though. Thanks for the explaination.

[The Orchid Boy]

Thanks for the explanation. Do humidity trays really work? I have a flat that seedlings go in and a heat mat. I might try filling the flat with water and put the heat mat under it and see how that works.

[naoki]

Originally Posted by The Orchid Boy

Thanks for the explanation. Do humidity trays really work? I have a flat that seedlings go in and a heat mat. I might try filling the flat with water and put the heat mat under it and see how that works.

I used to use them when I was in a more humid region because they made me feel better. But I don't think that they are effective. Is Nebraska pretty dry? If your room is small, an ultrasonic humidifier may work well to bring the RH up to 50-60%R (fairly low cost to operate). I prefer to use a simple humidifier without build-in humidistat (which seems to be inaccurate sometimes), and maintain the humidity with Amazon.com: Zoo Med HygroTherm Humidity and Temperature Controller: Pet Supplies

If your room is big, then you need some kinds of enclosure. This is what I use:
Amazon.com: LEDwholesalers GYO1009 60-Inch x 48-Inch x 24-Inch Mylar Reflective Hydroponic Grow Tent: Patio, Lawn & Garden

But if your area isn't extremely dry (e.g. < 40%RH), the grow tent isn't probably worth it.

[The Orchid Boy]

I NE, in summer all the transpiration(?) from the crops make it so humid you can hardly breathe outside the humidity is always above 75% and in my room around 60%. In winter the humidity outside is usually less than 20% and in my room the humdity stays around 38% to 50%. Does the humidifier leave residue from mist on the orchid leaves? Does it have to mist directly on the orchids?

[naoki]

If you use really hard water with ultrasonic humidifier, you may get white dust. But I use RO water. Evaporative-type humidifier won't create white dust, but you'll need to replace the filter. The humidifier humidifies the room, so don't directly blow on the orchid. With that much of humidity, you'll probably be ok although it is nicer to have a little more in the winter. It is weird why you get higher humidity indoor than outdoor in the winter. Usually it is opposite (warm indoor air CAN contain more water than cold air outside, so indoor RH is lower).

[GirlGoneWild]

With regard to humidity, I read an article once that said that one of the easiest ways to increase the humidity in your growing area is to group your plants close together. Apparently they create a "micro-climate" when put in close proximity, which produces higher humidity around the plants than if one was placed by itself in the corner.

I have mine grouped pretty close together on my landing, which functions as a virtual sunroom, since it has large windows on all sides and sun streams in and heats up the area all day.

I also have coco-liner (used for baskets liners and such) that's cut to fit the shelves of the plant stands. I mist these with water, and of course, when I water the plants the excess drains into the coco-liners, which I imagine helps to do at least something for the humidity in the area, considering there's a lot of shelving with moist coco-liners.

I should probably put my humidity detector in the area to find out what the humidity actually is there, but the plants seem very happy and everything is growing lots of leaves very enthusiastically.

I do, however, have a sulky miltoniopsis that only seems happy outside in the shade during the summer, in 80% humidity. As soon as I brought it inside when the weather got too cold, leaves turned yellow and the new growth turned brown. I have it in a humidity "basket" of sorts, which involves pebbles in water inside a high-walled basket (which I then put the plant pot in), to give it the maximum amount of humidity possible.

But so far, my milt. is the only unhappy plant out of oncidiums, dendrobiums (hard-cane and nobile), paphs, phals, catts, vandas (in vase culture), and a weird inobulbon-something that I got for free. So perhaps there is something to the "grouping" thing.

Especially since I live in Pennsylvania, and we get winters that are particularly dry. Oh, and I've heard that putting ferns in your growing area is GREAT for humidity. I have, unfortunately, run out of space for anything besides all the orchids I have stuffed in that small space, so I haven't had a chance to test out the "fern" theory. But anyway, grouping plants together seems less complicated that building/buying humidity trays and installing humidifiers, so hey, I figure it can't hurt to give it a try!

And my Sandie seems quite happy with the arrangement too! Of course, it will be a couple of years before it would bloom anyway, but it's enthusiastically putting out new, shiny leaves, so I guess that means it's happy!

I've heard many different opinions on the humidity issue...some say it's of great importance, others say it's not that big a deal...but I know my legs get itchy and dry in the winter, so I feel like I should do something to help my orchids out a bit, since I obviously can't slather them with Vaseline!

Anyone else have any thoughts on the "grouping of plants" or "adding ferns" suggestions?

[naoki]

I'm not completely confident about this "micro-climate" argument, but I may be wrong. You can easily measure with hygrometer (which is pretty cheap). I like the ones which displays min max as well as the current RH + temp simultaneously. I like this one: Amazon.com: Acu Rite Indoor Humidity Monitor: Home & Kitchen
The min max gets automatically reset every day, which is convenient, too.

If the transpiration rate (rate of water loss through leaf holes) of your plants are really high relative to the room volume, plants increase the room humidity. I happened to have 4 large gourd plants (and other plants) in 12x12' room, and the humidity can be 10-20% higher than the other room. I just checked RH: gourd room 62% and other rooms 39%. Then I measured RH in the middle of gourd jungle: 65%. So the "micro-climate" effect is only 3% increase. This is with leaky plants like gourds (these are called C3 plants).

It sounds like that your "sunroom" is really nice! If it is a relatively small, enclosed area, you probably are getting humidity benefits from putting lots of plants in there.

[The Orchid Boy]

I do have my plants packed fairly tightly under my T5 light. The RH near my plants is currently 43%, five feet away the RH is 37%. The RH outside my room is around 20% to 30%. I have a nepenthes (tropical pitcher plant) and they usually like very high humidity and cooler temperatures than I have. I've had it for quite a while and I saw it adapt over time. It made leaves that were waxier and a little thicker so the Paph. sanderianum may adapt too.