What concentration of fertilizer for daily watering of mounted orchids?
 

Some people, like Fred Clarke for instance, fertilize with every watering and do a monthly flush of pure water.

This both makes sense as it matches what happens in nature, and it's nice to not have to remember a fertilizing schedule.

I think he recommends like 1/4 tsp/gallon of MSU or around there for potted plants, but what about for mounted plants which get watered everyday?

mine get 1/3 to 1/2 in the daily waterings and the s/h

You need to specify what kinds of orchids.

People use is a huge range. If conditions are good for growth, some orchids do best with heavy feeding, and others will not tolerate it. You need to learn about individual genera.

Orchids may grow in climates cooler or warmer than they prefer, but not as fast as in an ideal climate. The same plant can use more fertilizer when growing rapidly in a good climate than slowly in a less-than-ideal climate.

For Cattleya seedlings in warm weather, Fred actually recommends 1/2 teaspoon of MSU per gallon of water / 5ml fertilizer powder in 3.78 liters of water. He lives in Vista, California, where it is very warm all summer long, and winters days are likewise usually quite warm. He is closer to the equator than most of the US, Canada and Europe, so he gets more intense light. His plants in his greenhouses grow much faster than his plants would in more northerly greenhouses, so it makes sense to give them more food.

I guess my question is: how do I adjust fertilizer recommendations for potted culture, to mounted culture?

Fred says he waters his Catts like three times a week, how does his fertilizer recommendation change for mounted orchids which are watered at least once a day, assuming the same weather conditions?

Oh... I don't think Fred has many, if any mounted plants. Fred waters so his plants don't go completely dry during growing season. Depending on your temperatures and humidity, you might need to water mounted Cattleyas 1-2 times a day. Mounted Catts hardly grow at all if they don't get enough water. I would fertilize on the same schedule as plants in pots. You're in Canada. If you have a nice warm greenhouse you can fertilizer 2-3 times a week. If it's not so warm I would cut back to every 1-2 weeks.

Many growers recommend fertilizing every watering as this is what occurs in nature... that was the whole point of this post, to figure out how much fertilizer I should use if "every watering" = everyday

That will depend on how fast they're growing. Orchids need very little fertilizer. Look at the fertilizer calculator in the Free Information section of the First Ray's Web site. It will help you figure out concentrations. You could fertilize at 5-20 parts per million nitrogen every day in the growing season.

Personally, for daily watering, I'd go no more than 25 ppm N; possibly as low as half that.

Divide 2 by the %N on the label for teaspoons/gallon for 25 ppm N. Divide 2.3 by %N for ml/L.