Nitrogen ppm for different genera

[terryros]

I know that most growers, particularly with larger mixed collections, like to use one fertilizer strength that is probably a compromise for different genera.

However, if you could optimize the fertilizer strength for each of the major genera do we have any good information on what that might be? Would Phrags be really low (50-75) and Phals really high (300)? Where would the others sit or do we mostly guess?

[Ray]

Aside from "vandas are heavy feeders" and "phrags being wary of high fertilizer concentrations", there's not a lot of guidance that I'm aware of, and actual data is even more sparse.

About the only actual study I've seen was by Dr. Yin-Tung Wang at Texas A&M, who found that about 250 ppm N was about the best for phals in his College Station greenhouse.

We do have to keep in mind that while 250 ppm N was fine there, a windowsill grower in New England will probably damage plants' roots if they fed it at that rate under those conditions.

Once again..... it depends!

[terryros]

In my basement plant room with fluorescent lights I have pretty close control of temperature (I have heat and air conditioning to it) and day length. It would not be a pain for me to create several different strengths of feeding solution for my s/h system. I have Catts, Phals, Paphs, Phrags, and a couple of Oncidium alliance. What is your guess about 2 or 3 different solutions that might optimize the feeding?

[orchids3]

Hi,
Maybe the plants should be telling you what they want - are you listening? If you are getting too much soft new growth then you are using too much fertilizer. If you are not getting growth then too little. Light levels make the differance. My fertilizer solution is baselined at 100 ppm for most plants and 125 ppm for cymbidiums and vandas. Corrections are made by what I see. Dont forget pH. If the pH is wrong the plants dont use the nutrients effeciently. You waste expensive fertilizer when pH is wrong because the plants cant use it. Not a simple answer but maybe it helps.

[orchids3]

Dont agree with you about the pH. You should be checking it even with RO water. Not only should you be checking what you put in to the plant but also the pH of
the media. Do that by checking the pH of the water in the resevoir after it has been ther for a few hours. In fact rain and RO water tend to be too acid. (Low pH). A cheap test kit from a hydroponics store is about $3.

[terryros]

Thanks. I think my problem is that I had about 10 years experience growing Phals in bark under lights a number of years ago. Now I am starting up again with a broader mix of things and using s/h. So, with new genera and new media I am not yet sure of what I should expect with some things right now. I am using 125 ppm N using Green Jungle 1-0-1 complete fertilizer (I support my local orchid green hourse) in RO water so the pH is good. I just thought that instead of waiting a year or so to see how things grew that I would try and optimize what I could right now. I guess I had just better keep doing what I am and see what happens.

[Ross]

Originally Posted by terryros

Thanks. I think my problem is that I had about 10 years experience growing Phals in bark under lights a number of years ago. Now I am starting up again with a broader mix of things and using s/h. So, with new genera and new media I am not yet sure of what I should expect with some things right now. I am using 125 ppm N using Green Jungle 1-0-1 complete fertilizer (I support my local orchid green hourse) in RO water so the pH is good. I just thought that instead of waiting a year or so to see how things grew that I would try and optimize what I could right now. I guess I had just better keep doing what I am and see what happens.

Good idea, when switching regimes. It sometimes takes a while for the plant to aclimate to the new regime.

[AaronM]

Try feeding them whatever you can afford and tell them "you'll eat what I give you and you'll like it , Mister/Missy!" That's what my folks did and I'm 6'4".
Seriously, I've tried finding a magic mix but it all seems to be coming down to me watching the plants and seeing what they need (like someone said earlier). Vandas seem to be one of the easiest to manipulate. When I want more roots I use a high phosphorus mix and when I want leaves it's high nitrogen. I think Vandas are the only orchids who bother to read all the orchid books.
I do recommend that you keep some kind of journal until you work out a good system. Without any records it's really hard to keep track of who got how much of what when and where. (Wow, my journalism teach from highschool would be so proud of that sentence.) If you don't keep track you'll never know what works best for your situation.

Good luck,

AaronM

[terryros]

I tested some fertilizer solution that was kept in my pump sprayer for two days and the same solution two days old in the saucer reservoir for a pot. They are not perfect, but my pool/spa test strips show that the pH is slightly lower in the saucer and the total alkalinity is also slightly lower. Neither is a dramatic color change but they are different. The total alkalinity is pretty low with each, which is not the case with our city water. Leaves me a little stuck. I knew we wanted acidic solutions rather than alkaline. Is your point that we want to be refreshing the fertilizer solution regularly because of the changes in the fluid or that we need to be doing something different at the start if pH is too low?

[Ross]

I wonder why we are discussing this? In the end the production of the plant matters. I have a very accurate pH meter that measure to hundreths. I used it a few times and you know what? Nothing I did made any matter to the plants. Whatever my regime is, they do just fine. Not to dis this discussion, but I really wonder about how important this stuff really is?