There is a lot of cultural information available on The American Orchid Society site - aos.org.  Below is how I grow.  It is the result of over 25 years of observation and reading about orchids.

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GENERAL

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Our greenhouse is outside Phila., PA.  Some of the information below may have to be adjusted to better suit your location.  On 6/21 the sun rises and sets almost directly over the middle of the greenhouse.  During the fall its arc slowly falls and the sun shines more and more into one side.  The importance of this is it creates microclimates that allow me to grow several types of orchids with different cultural requirements.

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We have a 32 x 75 greenhouse.  During winter, the minimum temperature goes down to about 60F.  During the summer, the max temps during the day are over 100F.  This extreme high temperature during the summer calls for some measures that you may not have to take if your temps stay in the 90 - 95F range.   There is a period in the fall when we allow the temperature at night to get down to 50F for a couple of weeks to help the Phals spike.

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LIGHT

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Year round there is 30% shading down the middle 20 feet (lengthwise).  At the beginning of March, I add another 30% on top of that which covers the whole greenhouse until it is removed at the end of October,    

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The foot candles in the middle of the house are about 1,000 - 1500, year round.  Along the sides (uncovered during winter and covered during summer as described above) run from 2,000 - 3000 depending on time of year and angle of the sun.

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You are much better off giving too little light.  The orchids won't die.  You may have to provide more light to make the orchids bloom.

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WATER QUALITY

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Without a doubt, water is the most important factor leading to good orchid growth. 

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We use about 90% RO water combined with 10% well water.  It is stored in a large tank so the water we actually use is about greenhouse temperature. There was a noticeable improvement subsequent to our putting in a RO system.

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FERTILIZER

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 Invest in a ph meter and a ms meter.   You should be able to find them on the internet for about $40 each.  Get some calibrating solution and calibrate them.

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Ph measures the acidity of your water.  Proper ph levels are necessary for orchids to be able to absorb the nutrition you are providing them.  We grow a mixed collection of orchids and try to get the ph of our water to around 6 - 6.5. There are products that can bring the ph of your water up or down to get to this level.  Many growers suggest measuring the ph of the water that flows through the pot.  I never did this.  

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An ms meter measures the electrical conductivity (alkalinity) by measuring of the water. (Very basically it calculates the  strength of what's in the water.)

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We have two distinct growing periods during the year.

1.  From about Feb. 15 - July 1 AND Sept. 1 - NOV. 15.  During this period the orchids put on new growth.

2.  All the other parts of the year.  During this period the orchids do not put on new growth.  

It is too hot in the summers and the orchids shut down.  In the winter, they bloom (in theory).

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During period 1. we us an ms of about .67 at every watering.  Very rarely, no fertilizer is used. (when I'm too lazy to make a new batch).  Ph is always adjusted to 6 - 6.5.

During period 2. we just use the well + RO water.  No fertilizer.  PH is adjusted to 6 - 6.5.  

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It is sometimes recommended that during the winter certain orchids be given a dry period.  We have found that in our greenhouse orchids will die due to dehydration if not watered during the winter.  They need to be watered less using NO fertilizer.

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We currently use Jacks 15-5-15 Cal Mag formula.  If your water, before adding fertilizer, has a low ms reading (under .2) this is a good choice.  If your water has a high ms reading (.7 or above) a good choice is probably Peters Pro 20-10-20 Peat Lite.  If your water reads between .2 and .7 Peters Excel Multi Purpose is a good choice.  There are a lot of good fertilizers out there.  

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WATERING SCHEDULE

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We are always asked "How often am I supposed to water my orchids?"  The answer is "It depends".  Most orchids can be safely watered when the potting medium has just dried out.  Others, like some Phrags, can sit in water.  Mounted orchids can be watered daily.  Orchids in New Zealand Sphagnum Moss need to be watered less than orchids in bark.  Small pots need to be watered more frequently than larger pots.  It's an art not a science.

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We water when the orchids are dry.  When you water, water heavily.  Then wait until the orchid is dry, then rewater heavily.  Watering too heavily will never kill your orchid.  Watering too frequently will.

 

 

POTTING MEDIUM

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We use New Zealand Sphagnum Moss for Phals, Oncids (and intergenerics), and as a backing for mounted orchids.

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All other orchids, except Phrags, are potted in a bark (Currently Orchiata) based mix.  It consists of 3 parts bark, one part perite, .5 parts charcoal and 1 part clay aggregate or lava rock.  For the fine root orchids the bark is the 1/4-1/2 inch size.  For the thicker rooted orchids it's 1/2-3/4 size.  This keeps it simple.

 

For the Phrags we use a coconut husk mix.  The CH is soaked overnight three times with our RO water.  The mix we use is 3 parts CH, one part clay aggregate, and one part charcoal.

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REPOTTING

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You should repot at least every two years.  We try.

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AIR MOVEMENT

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Air movement is very important.  Within reason provide as much as you can.  Not only will it help keep fungus and bacteria down, it also makes the orchids uptake more water through the root system.  It helps compensate for the humidity that's being blown off the leaves.  The water around the root system is where all the goodies are that we provide.