I need help with fertilizers - Don't know how to use them

[RosieC]

I flush with normal water arround once a month and I use fertiliser every watering between that. When flushing make sure you run lots of water through the pot, the idea is to flush out any build of of the fertiliser salts.

[LuizaG]

Hi Rosie, Tony (Britbloke) and Frostedeyes

Under thread called "How much MSU fertilizer to use (Repotme)" I have been advised that I should aim for 125 ppm N everytime I water. They say you find out how much fertiliser to use in order to get to 125 ppm N by dividing 10 to the value on N given by the label and it results in number on teaspoons of fertlizer per gallon (3.78 liter)

Orchid focus Grow has 2.2 N therefor
10/2.2= 4.55 (about 22.72 ml) teaspoons per 3.78 liters
or 6 ml per 1 liter

Given that information and the advice I got from you I am back in confusion. I really don't know what to do or what question to ask next...

[camille1585]

Originally Posted by britbloke

I would fertilize just as Rosie describes, about 1/2 the recommended rate. Most people fertilize weekly, the saying is "weakly (1/2 strength), weekly".

1/2 recommended rate (or 1/4 or other) means strictly nothing without knowing what fertilizer is used. When you're using a fertilizer dosed for 'normal' plants (such as a 15-15-15 for example), then saying to use 1/2 strength on orchids is somewhat accurate, but if you're using a fertilizer which is for orchids to begin with (like the one in question, 2.2-1.2-2.1) feeding 1/2 the recommended rate is basically like feeding them nothing.

[camille1585]

Originally Posted by LuizaG

Hi Rosie, Tony (Britbloke) and Frostedeyes

Under thread called "How much MSU fertilizer to use (Repotme)" I have been advised that I should aim for 125 ppm N everytime I water. They say you find out how much fertiliser to use in order to get to 125 ppm N by dividing 10 to the value on N given by the label and it results in number on teaspoons of fertlizer per gallon (3.78 liter)

Orchid focus Grow has 2.2 N therefor
10/2.2= 4.55 (about 22.72 ml) teaspoons per 3.78 liters
or 6 ml per 1 liter

Given that information and the advice I got from you I am back in confusion. I really don't know what to do or what question to ask next...

Yes, that calculation is absolutely correct if you are shooting for 125ppm N. A lot of people use that as their target value (as I do) while fertilizing at most waterings. Like I mentioned in the other thread, I use the same fert at 6ml/L on my orchids and they are doing wonderfully.

If you feed the 5ml per 2L like you mention earlier, then you are feeding them less than 60ppm N, which is less than even what people give fertilizer intolerant orchids like Masdevallias.

[britbloke]

We all pot,water & fertilize according to our needs and results.
I use MSU fertilizer (specially formulated for orchids using RO water). At 13-3-15 the grower (with many years of successful growing) recommends 1/4 tsp/gal once a week, which gives 44ppm of N using the calculator.
I'm not disputing that 125ppm is a commonly held target.
I can tell you my plants do wonderfully on that diet...

[Call_Me_Bob]

i shoot for 115 ppm N. because its always better to under fertilize than to over fertilize, not saying that 125 ppm N isnt a good number. i have some sensitive plants, so i just fertilize to the lowest common denominator

[RosieC]

Originally Posted by camille1585

1/2 recommended rate (or 1/4 or other) means strictly nothing without knowing what fertilizer is used. When you're using a fertilizer dosed for 'normal' plants (such as a 15-15-15 for example), then saying to use 1/2 strength on orchids is somewhat accurate, but if you're using a fertilizer which is for orchids to begin with (like the one in question, 2.2-1.2-2.1) feeding 1/2 the recommended rate is basically like feeding them nothing.

I agree. Mine is a rather unscientific measurement. If someone else has calculated the figures then I would go with that.

[camille1585]

Originally Posted by help

i shoot for 115 ppm N. because its always better to under fertilize than to over fertilize, not saying that 125 ppm N isnt a good number. i have some sensitive plants, so i just fertilize to the lowest common denominator

125ppm is far from overfertilizing, unless you are only dealing with masdies and other salt intolerant orchids. 125 is meant to be an average that will work for a collection with orchids having varying food needs. On French forums, growers have recommended shooting for 100- 150ppm (the high end having no ill effects) and only 90 during the winter when plant growth is extremely slowed down for most people. Professional growers who have optimal cultural conditions,( so optimal growth) push it as far as 250ppm N. We dont have those conditions so that amount would burn roots. Just goes to show how much influence culture and environment has on the plants, and how it affects the way we should feed them.

[Call_Me_Bob]

that is a big difference! but i have some salt intolerant 'chids, so its just easier for me. to make it lower

[camille1585]

Originally Posted by help

that is a big difference! but i have some salt intolerant 'chids, so its just easier for me. to make it lower

I agree. If you have a collection of mainly salt intolerant orchids, then it makes more sense and is easier to use less. You can always give the others more once in a while. But for me 99% of my plants are in the intermediate range of salt tolerance/need, so it makes more sense to use a higher amount for everyone. Once in a while during the growth season I give my food hogging cyms up to 160ppm N.