Nitrogen ppm for different genera

[terryros]

I think you are probably right but I suspect that some of our temperaments are pretty scientific about this (clinical investigation is part of my career) while others are probably more artistic/intuitive, just watching and doing what seems/feels right. I can't shake the thought that this is biology and there are variables that someone must have studied. I am probably wrong.

[Tropic]

Observing the orchid plants and their growth on a regular basis gives me a good measure of their reaction to the fertilizer and watering regimen that is used in my greenhouse. New growth strength and root tip development, leaf color and resistance to pests will be judged depending upon years of experience and a bit of the old 'green thumb' feeling. With seasonal changes and gradual variations in orchid bench plant associations, there has to be a variety of effects that will seriously influence the desire for a uniform program. It is never cut square and dry ... this is what makes orchid growing such an enjoyment and challenge for me.

[orchids3]

Plants take up nutrients best when the pH suits them but that doesnt mean they wont grow and bloom when the pH is other than perfect. I find that low pH does lead to dead and rotten roots. There is a fine article in the last Cymbidium Society Journal written by and Australian who grow his cymbidiums in shallow pans - a lot like the Semi Hydroponics technique. He states that in his opinion pH adjustment is even more important than fertilizer and from my experience I agree with him. Maybe you local Orchid society will have the CSA journal on file.

[terryros]

I am using RO water and a fertilizer specifically made for RO water, at least equivalent to the MSU formula. Shouldn't the pH be fine. I have only seen things where people are trying to lower the pH. What do people do to add alkalinity/pH?

[Ross]

If you need to add alkaline (pH up) then a product sold at Home Depot called ph Up (Duh) is a good choice. Being for ponds, it's clearly safe for orchids.

[Royal]

Frankly, I kind of agree with Ross on this one. Rain water is acidic. My tap water is not. My plants seem happy with either.

terryros, You can bring pH up with a bit of baking soda. Just make small additions at a time, a little bit can prduce a big swing, especially in RO water (no pH buffers).

[orchids3]

I like the MSU stuff and my water is pure enough that the pH did chech between 5.8 and 6.2 per Dr Argo's articles on the subject I used the RO water mix. Got complacent about checking the pH dropped (My well varies during the year according to rainfall) and I killed a lot of roots before I checked again. Its best to spot check pH every so often. I use 17-5-17 Cal Mag now and do adjust pH slightly. If you feel OK not doing it then thats fine but it is very easy to check and adjust. Orchids are grown in all kinds of water - understand a grower in St Barbera grows with water that has 1800 ppm TDS. Mine checks 300 ppm contaminates but once grew orchids in Calif. A lot depends on what the contaminates are so the discussion that some things can or cant be done is all believeable. It just so easy and so productive to check and control pH.