Does anyone have a quatitative description of 'good' air circulation?

[spiders_r_us]

I have a question about air circulation. I just got my first orchids and I want to house them in my terrarium with ferns.

How much circulation is considered as 'good' circulation? Is it quantifiable? Can one create too much circulation?

I see photos where there are one or two 12V CPU fans for a 1.5'x1'x1' set up. My terrarium is 4'x2'x2' and I would like to find out how feasible is it to house these wonderful orchids in the terrarium.

Cheers.

[King_of_orchid_growing:)]

No it's not quantifiable. Most people judge visually.

If the leaves or spikes are moving about gently to a slight breeze that's good enough. Any more is too much.

However...

I do know the two orchids you have are native to your homeland of Oz.

They're both lithophytes (which means they grow on rocks).

Here's a pic Dockrilla striolata in the wild:

Dockrillia striolata 041107-2937 on Flickr - Photo Sharing!

I own a Dendrobium kingianum and they are grown in diatomite. But you don't need to grow in diatomite. Small pieces of sandstone or granite will work just fine.

[spiders_r_us]

Hi, thank you very much for your reply and for the photo. Now I can have a mold free terrarium and the orchids can be happy too.

Could I ask another question?

Would S. kingianum grow on granite as well?

Thank you.

edit - Oh, I didn't read the 'granite will work just fine'.
Ta.

[Andrew]

Is there a reason you can't grow them outside? Throughout most of Australia, both kingianum and striolata will perform much better if grown outside rather than in a terrarium. I remember one of my old university departments having a kingianum in a paludarium under MH lights. On the plus side it was alive, on the negative it was probably the poorest example of a kingie I have come across; it never flowered and I can't recall it putting up many new canes in the 6 years I was there. Both species require cool winters and bright light to flower so while you may have better luck in getting it to put out growth than the guys at my university, I suspect it will still be an uphill battle to get them to flower under indoor terrarium conditions even with supplemental lighting. If you're looking for something to go in a terrarium alongside ferns I'd be finding a warm growing orchid with lower light requirements. Maybe you could look through the terrarium section of the forum for ideas.

[spiders_r_us]

Originally Posted by Andrew

Is there a reason you can't grow them outside? Throughout most of Australia, both kingianum and striolata will perform much better if grown outside rather than in a terrarium. I remember one of my old university departments having a kingianum in a paludarium under MH lights. On the plus side it was alive, on the negative it was probably the poorest example of a kingie I have come across; it never flowered and I can't recall it putting up many new canes in the 6 years I was there. Both species require cool winters and bright light to flower so while you may have better luck in getting it to put out growth than the guys at my university, I suspect it will still be an uphill battle to get them to flower under indoor terrarium conditions even with supplemental lighting. If you're looking for something to go in a terrarium alongside ferns I'd be finding a warm growing orchid with lower light requirements. Maybe you could look through the terrarium section of the forum for ideas.

Thank you for your suggestion. It's gonna be pretty hot and dry outside and they are so small (<5cm), would they stand a chance? I am frequently away so I can't always water them. I can keep them on the kitchen window sill but due to health reasons its best not to.

My terrarium gets natural light all day (most in the evening) plus I have a 40vtube to supplement light, there is a stream and a pond to help with humidity. All the plants in the enclosure are local so there is no heating.

I don't need to have them in the enclosure but just thought it'd be nicer for them. If my terrarium isn't good for them then I will look for an alternative option to put the two orchids.

Thank you for bringing this forward and now I don't have an excuse if they died in the terrarium.

[King_of_orchid_growing:)]

The two species of orchids don't really need to be watered as frequently as ferns do.

1. The Dockrilla striolata has leaves that are succulent looking. They can withstand some drying.

2. Den kingianum has roots that rot easily if they're watered too frequently. Like I said, they don't need to be watered as much as ferns do. They have those thickened canes that store water and food (look at the bottom of the canes they're wider than the top part, that's the storage area).

I'm growing my Den. kingianum outdoors all year round here in Southern California, USA. It can get blistering hot in the summers (occasionally over 100 F/over 38 C during the day - it's usually in the mid 90's F during the day/32 C, however).

It can get pretty cold here too. In the winters at night it can drop down to 36 F to 45 F (2 C to 7 C). Usually it's around 45 F (7 C).

My Den. kingianum gets full sun.

Had it for a couple years. It's real big! Got it at half the size.

Real easy to grow. I often let this guy do it's thing. Don't really look after it as much as some of the other orchids in my collection.

I have the tall variety. There's also a short variant that originates from a different region of Australia.

[Ray]

Back to the original question for a moment - I'm sure that proper air movement can be quantified, but it may not be of practical use.

Under otherwise ideal conditions, what you're shooting for is a gentle, tumbling air movement that eliminates stratification and pockets of stagnation. Too little, and you don't do that. Too much and you risk drying the plants out too rapidly. In less than ideal conditions, air movement can be used to enhance drying or cooling, as needed.

A couple of decades ago, the use of "turbulators" in greenhouses was common. Instead of blowing air linearly down the length of the greenhouse, for example, they had very irregular, horizontally-spinning blades that pushed air around in irregular, tumbling "pockets".

[Andrew]

Originally Posted by spiders_r_us

Thank you for your suggestion. It's gonna be pretty hot and dry outside and they are so small (<5cm), would they stand a chance?

If you're north of Sydney you can probaby get away with full sun in summer but if your in drier areas such as WA, SA or Vic give them the equivalent of around 50% shade. Even adult plants will burn in the hot, dry sun of southern Australia. If you're in Tasmania the cooler temperatures may allow you to give adults full sun in summer but seedlings would probably still do better with some shade. While they're still seedlings, if you're going to be away for more than a few days during the height of summer, give them a good water before you leave and put them in a cool shady spot until you get back. In about 2-3 years when they put on a bit of size they should be OK to leave without giving them additional protection.

[spiders_r_us]

Thanks everyone with the help.

Hi Andy, I'm in Victoria as well. Would the orchids be healthy in the long run if I kept them indoors?

Here are the little orchids. They have been sitting in the house for two weeks now and they seem to be doing well. They have even grown new shoots since I've been away for a week.

[The Orchid man]

i think you should approach this apparant problem from a different perspective. plants grow using carbon dioxide and transpire watervapour and gasses - in my view air circulation should be such that a slight but relatively constant flow of air across a leaf surface would suffuice to take away that which the plant gives off whilst constantly replenishing the carbon dioxide needed to grow. a constant movement of air also helps prevent fungal spores from settleing and causing problems, although i suspect that you have the appliance at a temperature not too conducive to this. just a thought! peterD.