fertilizing regimen question

[frostedeyes]

I know each of us have our own feeding regimen. Some does it weakly weekly, while others fertilize twice a week. and to some including me or maybe just me! haha! feed their orchids everyday. I add less than 1/2 teaspoon per gallon everyday.

So question is... why should it be weakly weekly and not daily? whats the diff on it? I hope Ray would post an answer lol!

[camille1585]

I think weakly weekly essentially means weakly at each watering. That's how I understand it and that's what I do. It just so happens that I water weekly at this time of year.
While watering daily may be necessary where you live, in temperate climates we water much less. The only ones that I do water daily are the mounted orchids, and even they don't get fertilizer everyday. I fertilize them every 2-3 days and use plain water otherwise. Be careful about fertilizing everyday, all the time. You should flush the pots fairly regularily to stop excessive salt buildup. I flush them every 4-5 waterings.

[Ray]

First of all, we should understand that the "weakly, weekly" concept was not created as a way to space out ffedings, but as an alternative to what was the norm of feeding a strong fertilizer solution, but at fairly long intervals - monthly being common 20- or 30 years ago.

I don't water daily, but I do feed every time.

Where the caveat comes in is with the mass of nutrient applied. Unfortunately, that creates an interface between a calculation and a wild estimate.

Let's say I feed at 125 ppm N (125 mg/1000g), three times a week, and that all of my pots of plants plus medium retain 250 ml of solution at every watering. I don't know the actual density of my solution, so let's assume it's 5% greater than that of water alone. That means that when I water, the pot is retaining 250 ml x 1.05 = 262.5 g of solution. The mass of nitrogen, therefore, is 125 mg/1000g x 262.5g = just under 33 milligrams. So in a week of feeding, I have provided about 100mg of nitrogen to each of the plants.

Of course, such a calculation of the mass isn't really applicable, as the pots are different sizes, the retention varies with medium or medium condition, pot drainage, etc., so I would simply estimate the concentration needed comparing before and after feeding regimes, observe, and adjust as needed.

If I am happy with the growth and flowering of my plants at that 125 ppm N rate applied 3x/week, and want to water daily, I would cut my fertilizer concentration to 3/7 x 125 = about 50 ppm N.

[frostedeyes]

oh all right. coz here in my area i really do need to water my plants daily. anyway im still confused with your numbers. haha! seriously am pretty dumb with the PPM lol! sorry but anyway i hope im doing it okay. thanks ray.

[Ray]

Most folks are used to making recommendations like "use at half strength", but that is meaningless, as you don't know half of what.

By working with an actual concentration of something, it becomes easier to actually control what you're doing. As nitrogen is the biggest nutrient applied, it becomes the convenient measure, so we end up controlling the fertilizer calculation in ppm N.

In reality, if you are seeking a specific maturation date, such as is the case of growers of seasonal crops like food or decorative stuff like poinsettias - the single biggest cash crop in the US - you have to target the mass of nutrition applied over a finite time span. Using poinsettias as an example, the cuttings are usually planted in late August, with a target "harvest" in late November or early December, and in that time period it is the "norm" to apply 0.5g N via the fertilizing regimen.

They have very good knowledge of the holding capacity of their potting medium and the volume ofg it in each pot, so by balancing the watering frequency and solution strength, they can target that mass of nutrition over the time period.

[maitaman]

Whatever regimen you use, remember that nitrogen is generally very highly soluable while phosphorus is generally not, so remember to leach regularly or you will poison your plants. Most people tend to either not fertilize or to fertilize too much. Orchids are adapted to sporatic fertilization, not a regular input. Hybrids have been bred for a steady regimen - which is why they don't tend to do well in "normal" conditions in nature.
Also: those orchids that need a rest period do NOT need fertilizer during that time. Many Dendrobes, for example, will grow wildly with steady fertilizer but will not bloom. They will then die after a couple or three years.
For species it is better to under-fertilize than to over-fertilize. For hybrids you have to consider the types and parents.

[frostedeyes]

YEHEY REY! ok i got my PPM well not exact coz i dont know how to do the math anyway im using peter's 20-20-20 and since i water mine daily (except if its raining) I use 1/2 a teaspoon of fert in a 5 liter of water. well since i dont know the math thing i think its within 100-150 ppm of N, if my calculation is right! anyway i just need to remember that sunday is flushing day! since 6 days of 1/2 teaspoon daily is equal to 1 Tablespoon in a week and i think reading on the instruction it said that it should be fed weekly.. anyway thats all! LOL! btw! i tried the PETER's root and bulb booster well im not happy with the result coz i dont see any dramatic change. anyway but i found out that it does work well with grammatophyllum! after fertilizing the plant it just shoot 4 siblings! anyway just wanna share my observation on the root and bulb boost on peter's.