Greenhouse culture

[Kmac]

So, with nearly 300 orchids in the house, it was time to get a greenhouse. Mine went up in November, and I have a question: Do you run the fan only when its hot? Only when the mist system is on? All the time?

Any other tips for a new GH owner?

[jeffrey6115]

I have 2 fans that run 24 - 7. Another I have another in a hot corner that comes on by thermostat and of course the main exhaust fan that comes on when the temperature hits 80 degrees. This is in a 12 x 16 greenhouse. You should have some type of continuous air movement.

[raybark]

What you do is dependent, to some degree, by the details of the greenhouse operation, but I agree with Jeff - keep air circulating 24/7.

Then there's exhaust, swamp cooler or wet wall, shade cloth, etc.

Tell us more about the greenhouse itself, it's location, etc., and maybe we can make some intelligent, specific suggestions.

[Kmac]

Thanks, guys. It is 12x16, with concrete footings, and a decomposed granite floor, which holds moisture well. Walls are twin-wall polycarb. It has an automatic mist system, automatic vent/fan to pull hot air out, and a swamp cooler that comes on if temp reaches a set point.

The orientation of the greenhouse prpbably isn't ideal, since I had to deal with the only spot I had. The door end faces south, and the other end faces north. 60% aluminet shade cloth.

I grow a bunch of catts, and oncids, plus a bit of this and that...

Thanks for any suggestions.

[jeffrey6115]

You will learn as you go along that there are microclimates even in a greenhouse that size. You will also learn which plants like those climates and move them around till they're happiest.

[Brutal_Dreamer]

I agree with the others. Keep the air moving all the time - warm or cool temperatures. We have four large fans that blow down in the greenhouse and one that spins the air around. We have two exhaust fans - the one normal one in the highest part of the front for the kool cell and an extra one (twice as large) for pulling more hot air out at bench level. The leaves on the plants in our green house constantly bounce and/or move. This means we have to water a bit more often since we do not have a mist system, but we do not get fungus issues from plants being wet too long.

cheers,
BD

[raybark]

I'll say this - it sounds like your setup is well-planned. I actually think your north-south orientation is ideal, as that offers maximum exposure to the sun's rays dawn 'til dusk.

At this point, I don't know what else to add, but we can certainly take a stab at specific questions you may have.

[Kmac]

Thanks, guys. Ray, I appreciate your comment about the planning...it did take me a while to plan & save for it; glad it sounds like a good setup. Bruce, I have wondered if that one exhaust fan will be enough, as it does get a mite warm here in the summer. But people say it should; we'll see. Jeff, I am indeed finding "microclimates, and experimenting.

The only real probelm I have found is that the south end gets enough late afternoon sun coming thru the end to burn the fitst few plants a bit. That is the one wall I had made of glass, not polycarb (as it is the one I see, and wanted to be able to see in & out). I may need to adjust as the light gets stronger during the summer.

[raybark]

1) You might consider moving brighter-light plants to that south end, as it will always get more light, morning to evening, summer to winter. Up here in PA, with my local geography and trees, I don't use shade cloth, but actually have vandas hung high in the greenhouse to provide the shade to those below.

2) Your vent fan and swamp cooler should work together. For example, the swamp cooler should come on at one temperature, and the fan at a higher one. However, if the fan shutter doesn't open until the fan comes on, you might be restricting the air flow and limiting the effect of the swamp cooler. In my greenhouse, for example, the vent shutters and the fan work independently. The former are on "wax motor" solar openers, so start to open when the interior temperature reaches 65°, and are full open by 75°. That allows free air flow through the greenhouse all by itself, but if the temps continue to rise, at 85°, the exhaust fan kicks in.

[Brutal_Dreamer]

In addition to what Ray adds, our exhaust fan has two speeds. Ours kicks on at the lower temperature on the low speed and goes into high speed when the temp rises to a predetermined amount. The flaps on the kool cell are motorized and open when temps reach the lowest setting, the water pumps turn on when the exhaust fan is triggered on the lowest setting.

As for shade cloth. Since we have no trees around the greenhouse, we have shade cloth wrapped around the west side and over the full top. Not very pretty compared to the design of the greenhouse we built, but necessary to keep plants from burning. And like Ray, we hang vandas and cattleyas high in the greenhouse over the benches where we grow most everything else.

cheers,
BD