When to use what media?

[King_of_orchid_growing:)]

I really appreciate your enthusiasm for rice hulls John. And I'm sure it works. Actually this is a much more ecologically sustainable practice than using fir bark...Not sure why it hasn't caught on.

But for "kaitala" (aka Stephi) to understand, I'll start a little "slower"...

She has to understand the principles at work in order to understand why so many growing methods and potting media works.

[King_of_orchid_growing:)]

First thing's first...

Phalaenopsis.

If you've been digging in old posts, I'm sure you've come across many of my postings with links to photos of Phalaenopsis growing in the wild.

If not, here's a link to photos showing how they grow in the wild:

Phalaenopsis in situ - Flickr: Search

Notice what is going on.

They're growing in an Asiatic tropical swamp forest on wet tree trunks with little to no moss on them.

1. The moisture is consistent.

2. The roots are exposed to air.

3. The humidity should be rather high in this environment.

With this in mind, when growing them you must take these principles into consideration:


1. Proper humidity levels. Which would be 50% - 100%.

Why?

A. They grow in tropical Asian swamp forests. Which means that because of the tropical heat, the water from the swamp will evaporate filling the air with moisture, thus creating a humid environment.

B. Most of tropical Asia, especially places such as the Philippines, Malaysia, and Indonesia, are surrounded by large bodies of water (namely, the South China Sea, the Philippine Sea, the Celebes Sea, the Java Sea, the Andaman Sea, etc.). This means these bodies of water are also contributing to the humidity.

Here's a map of Asia:

http://mabryonline.org/blogs/howard/...heast_asia.jpg

C. Humidity plays a role in preventing water loss through plant respiration. Keep in mind, I'm only giving you a ridiculously simplified idea of plant respiration. It's actually much more complex. If you wanna know about it, I recommend taking a class in botany.

D. Because humidity is moisture in the air, the Phalaenopsis is provided with a source of consistent moisture when it is not raining.



2. In principle you must imitate a Phalaenopsis's habit of growing on wet tree trunks with little to no moss.

Yeah...yeah...They grow on wet tree trunks, what's the big deal?!

A. Very big deal. Without knowing this you won't understand the basic principles of what's happening. Therefore you can't imitate it.

B. The tree trunks are in the swamp water. They're wicking up the water from the swamp water. But they're being kept wet by the humidity. Without the humidity, even if the tree trunks are wicking up the water from the swamp water, it won't be kept wet for very long, and the water would not make it up so high.

Here's a scientific term for you...the above mentioned principle deals with something called:

capillary action



3. What's the big deal about the "little to no moss" thing. Why emphasize it so much?

A. Living moss secrets acids. Dead moss retains it's acidity. The pH of moss is very, very low (around a 3 or 4 on the pH scale - if you remember your chemistry, the pH scale is on a logarithmic function of base 10).

B. Not all plants grow in such acidic conditions. While Phalaenopsis do grow in an acidic environment, it is only slightly acidic (it's tolerance of acidity probably lies around the high 5's to mid 6's, and it can even handle a neutral pH).



4. Now to address the issue of air exchange.

A. Plants respire. There needs to be proper gas exchange for proper photosynthesis to occur. Without it, there'll be complications.

B. Many people are aware of a plant's leaves needing air. Not many people understand that a plant's roots need air too. This goes for all plants, not just orchids. That's why if you own a lawn, you really should be aerating it every now and then. This is why burrowing animals and insects are important for terrestrial plants.

C. If you're paying attention to the photos of the Phals in the wild, you'll notice that the roots are totally exposed to a large amount of air. But because it's growing on a wet tree trunk and it's humid, the air is not saturated with high levels of oxygen (remember this, it's important).



5. Air.

A. The air in certain non-tropical areas are usually not quite as humid as that of a tropical swamp forest, especially if they're not around adequate amounts of water or significant bodies of water. Which means other gases are more abundant in the air. While this is important to the grower, it's not quite as important to quantify it.

B. If the air is drier, then it poses problems for a plant that has adapted to a humid environment that is consistently moist. This is because the drier air is taking up moisture rapidly.

C. When the air is drier, water loss during plant respiration is also greater.



6. Monsoons.

A. Here I'll pull up a definition of what monsoon means.

"A monsoon is traditionally defined as a seasonal reversing wind accompanied by seasonal changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation. The major monsoon systems of the world consist of the West African and Asia-Australian monsoons." - (http://en.wikipedia.org/wiki/Monsoon)

B. Places where Phalaenopsis grows experiences monsoons. Meaning there is a wet season, and a relatively drier season.

[King_of_orchid_growing:)]

I can't help you with Mediocalcar decoratum. I don't quite fully understand it. All I know is that it is from the mountainous tropical rainforests of Papua New Guinea and that it's an epiphyte. Probably growing on moss covered trees.

[King_of_orchid_growing:)]

Dendrobiums...

This is one of the larger group of orchids in the bunch, so I can't give you general information...

Here's an idea of what I'm talking about:

"Dendrobium is a huge genus of orchids. It was established by Olof Swartz in 1799 and today contains about 1,200 species. The genus occurs in diverse habitats throughout much of south, east and southeast Asia, including the Philippines, Borneo, Australia, New Guinea, Solomon Islands and New Zealand. The name is from the Greek dendron ("tree") and bios ("life"); it means "one who lives on trees", or, essentially, "epiphyte"." (http://en.wikipedia.org/wiki/Dendrobium)

However, since I kinda have an idea of what you've got, I can make a guess at it.

It's probably closer in cultivation to this:

Dendrobium sp. on Flickr - Photo Sharing!

Take what you've learned about with the principles outlined in Phalaenopsis, and use what applies for Dendrobium.

The difference being is that Dendrobiums do not necessarily come from swamp forests. I think the multiple species that make up your hybrid are from mountainous rainforests.

[King_of_orchid_growing:)]

So how does all this help determine what media to use?

This is too broad of a topic.

All I'll say is look into the pH of the media.

Then research how the product works.

As a quick example, semi-hydroponic potting media is inert (it won't degrade like organic materials do and has a stable pH that's most likely neutral - pH 7.0). And it works on the same principles described for Phalaenopsis.

[Brookpoint]

Good info, can you tell me where you can buy rice hulls, thanks, Brook

[johnblagg]

I get mine free directly from the rice grainery here where I live ,but they are available online I will look and see if I can find a link for you.Meanwhile just google them and you will surley find a seller.