Suggested Greenhouse min and maxs for mixed species?

[scottfar]

Hey all! Been growing in a greenhouse for about six months now... we're getting into the summer here (northern California.. 2 hrs inland from San Francisco.. in Sacramnto (home to Arnold) (has hit 90 plus twice already this year).

Just wondering what everyone's thoughts are as to min and max temps. I know, I know.. theres cool, intermediate and warm.. and know the min and max for these... I have MOSTLY cats, but a little bit o everything, esp cats and oncidiums (some warm growing ones and others intermediate). have a few phal and paphs and other stuff, too.

We get VERY HOT summers here... over 100 is very common.

Greenhouse is 8x8 with 9' roof. Solexx panels. This is my first greenhouse..but I've already outgrown it. I'm in the process of saving up for a 16x20. Then I'll make my 8x8 a cool growing.

Struggled through the winter till I found what temps I wanted at night... (you might recall a drop to near freezing for my plants.. with no deaths! I'm pleased to say that 100% lived and even those REALLY stressed (loss of roots, leathery leaves) all show new growth of leaves/shoots and roots).

anyhow... back to temps. I've read all the mins and maxs and differ. temps... but any experienced greenhouse grower want to comment on what my TARGET temps should be?

Currently I keep it above 55f at night.. usually closer to 60-62 and have a powered exhaust fan that comes on at 75 and my swamp cooler set to 78 (which usually keeps it around 82 THUS FAR ...with temps in the upper 80s to low 90's... not sure when it gets to 115 outside what it'll keep it!).

I've been experimenting with shade cloth.. currently have just over top and east/west sides and partial South 78% (that's what was available at local box stores).. but find that even at midday it drops the footcandles wayyy lower than I'd like... so just ordered (and received but haven't installed) a 50%. My greenhouse is solexx panels (white).

WHERE should I put the temps, if at all possible, max, during the day? Should I aim for 75? 78? 80? 85? knowing that at some point when its 110 it might be 95?

have the fan coming on before the swamp cooler... but it seems to blow a lot of cool air out.. swamp cooler is near floor and 12" powered exhaust fan is at peak (about 7.5 off ground). Fan shutters open when swamp cooler is on even if fan motor isn't running. Should the fan come on at a higher temp to just let air escape and not be forced out?

The swamp cooler is set to a thermostat (man that was a nightmare. Got it hooked up correctly the first time.. then realized I hadn't put it in a waterproof box.. carefully drew diagram showing the 15 different colors of wires... and coded each nut... only to spend 3 hours trying to figure out why it didn't work when I put it back together--- heads up, it was a broken wire that stuck out of the plastic coating...but had broken a fraction of an inch back.. sometime it'd work and sometimes not...) The swamp cooler has a 2min prewet cycle then comes on. When it was in the low 80's low fan was enough.. but in upper 80's it needed high fan to bring it down to 82.

I've installed a misting system, too.. but haven't fully hooked it up. Have thermostat I'll plug a cycling timer on... nozzles are about 24" above MOST plants. What temp should I have this come on? How often should I have it mist (every 15 min, 30 min, hour? ...???) and for how long? 30 seconds? I usually mist each morning and notice it drops temp FAST.. but don't want plants soaked and getting fungus or molds.


ok ok, lots of questions... too many I guess for ONE thread. THANKS in advance!


--Scott

[Lizgeo]

I live in Houston area. We have long and hot summer, many days above 100. Once I visited a local orchid greenhouse and asked them if the heat was a factor. They handle the heat by providing more shade duing hot summer months.

[wetfeet101b]

Hi Scott,

I grow orchids in a greenhouse here in Southern California and although our winters are milder compared to you guys up north, our summers can be more brutal in the inland regions where I live.

In the winter, I have a heater that is set to keep the greenhouse above 55F. I dont have any plants that require warmer nights than that.
Without the heater, the GH interior could drop down to 40F.
Winter days are not a problem as outside temps rarely exceed 65F and the GH stays under 75F without supplemental cooling.

In the summer, we get very high temperatures and low humidity.
I can only apply so much shading to the greenhouse before I start losing valuable sunlight spectrum.

This is what I use for shading:
Single layer of Aluminet 50% shade fabric on the exterior of the greenhouse.
Single layer of generic 50% shade fabric at select locations on the west side of the greenhouse to protect some of the plants who do not like very bright light.

I also have an exhaust fan that is connected to a thermostat to activate it once the GH hits 80F.

I chose to use the low humidity to my advantage.
I set up an automatic mister with a programmable timer to help cool down the greenhouse and add some humidity.

So in terms of results, this is what I get with the current greenhouse setup.
If at noon, the outside temperature is 100F:
*Shade materials reduce the interior temperature to 95F.
*Exhaust fan and interior circulation fans help further reduce the temperatures down to around 90F.
*When the misters activate, they drop the GH temperature down to around 85F. After the misters stop, the temperature slowly climbs back up to around 90F.
* In the summer, I have the misters scheduled to run for 10 minutes every 30 minutes. So during the day the GH temperature would go through the 85F-90F cycle as the misters activate every 30 minutes.

On very hot days, I go to the greenhouse in the morning and soak everything with a garden hose. This gives the plants extra water and moisture to make it through the heatwave.

The orchids are doing well under this setup, it just needs periodic adjustments and intervention with a garden hose when a heatwave strikes.
However, this greenhouse is not meant for any "cool growing" orchids.

I hope this helps,
John

[Ron-NY]

I am growing in an intermediate greenhouse. the low is 60 and high is 80

[scottfar]

Thanks, everyone.