Decisions on Tap Water vs Rain and fertilizer

[shade131]

So I’ve been reading a good bit about all of the factors involved in nutrients and water chemistry, and more I dive into it the more confused I become! Some advice would be very much appreciated! What I am after is a fertilizer and water regimen that I can apply to all of my paphs and phrags - if possible. These range from maudiaes to brachy/parvi hybrids to multifloral. And a few phrags. parvi hybrids are largest groups. All are grown in a mix of half small bark and perlite, charcoal, Leac in equal amounts.

I am basically debating between using MSU and rainwater, or tap and MSU or some other as yet to be identified fertilizer.

Here is the analysis of my tap water for Atlanta, ga.

pH 7.5
Total Dissolved Solids (TDS) Est, ppm 91
Electrical Conductivity, mmho/cm 0.15
Cations / Anions, me/L 1.3 / 1.2

ppm
Sodium, Na 11
Potassium, K 3
Calcium, Ca 10
Magnesium, Mg 2
Total Hardness, CaCO3 33
Nitrate, NO3-N 0.7 (SAFE)
Sulfate, SO4-S 6
Chloride, Cl 12
Carbonate, CO3 < 1
Bicarbonate, HCO3 26
Total Alkalinity, CaCO3 22

Based on these variables, do any of you have any thoughts or recommendations? I’ve been using a quarter strength 20-10-20 urea free fert with tap with decent but not great results....

Thanks!

 

[tomkalina]

Ray Barkalow can help with this. Good questions.

 

[Ray]

I think Tom is giving me too much credit for my knowledge in this arena.

First and foremost, fertilizer, in my opinion, is VERY low in orchids' "Maslow's hierarchy" of needs. I believe that water (quality AND volume given), light, and temperature play far more significant roles in plant health. Fertilizer will rarely, if ever, fix a problem, and "more" is never better.

When diagnosing plant growth issues, fertilizer is one of my last considerations.

Based upon that analysis, your water is pretty good. The pH is a shade high, but nothing to be overly concerned about, and it will probably drop upon the addition of most fertilizers. That said, if you have the capability of collecting rainwater, I always default to using purer water, if possible, recognizing that you'll need to add everything back in via your fertilizer. I also recommend doing that with a tiny amount of fertilizer in every watering, using one that contains adequate levels of both calcium and magnesium. Personally, I like K-Lite (12-1-1-10Ca-3Mg), but you'll find lots of pro and con opinion on the use of that formula here on this forum, and I'll repeat my comment about fertilizer's relative lack of importance...

You hit my "hot button" with the "1/4-strength" comment. Even with the formula, that tells us nothing about how much you're giving the plants, and you didn't say how often, either.

Tell us more, as well as what potting medium you're using, how often you water and feed, and more about your growing conditions, and I'm sure we can be of more help.

 

[shade131]

Hey Ray - thanks for the response. I definitely agree with you regarding the relative importance of fertilizer. I learned that long ago with gardening and other tropicals. If you get the other elements right fertilizing becomes a matter of just not screwing it up.

Your questions - I grow all of my orchids under LED's in a garage that luckily has the seasonal variations in temperature that help induce flowering. 70-55F in winter, 65-80 summer. 12hrs late fall-early spring, 16 hours rest of the year. In addition to the LED fans, I have a couple small ones that constantly move air over the top of the plants. A lot of humidity trays and I splash water on the ground daily.. 50-60% in winter, 70%+ rest of year.

I'm currently using repotme's Imperial Phrag/Paph mix. I don't know the ratios, but it's roughly half small orchiata pine, the rest equal parts small lava, medium perlite, and .5in hydroton ( clay balls). It's ok but I might switch to something with bigger pieces for more air flow since I tend to over water.

Watering - mostly I try to water when they need it. Been using tap except for my two phrags. I let the parvis and multis dry out a bit more in winter. I fertilize at the aforementioned quarter strength every third watering. When not fertilizing I first give them a good soaking, and then go back through a couple minutes later and do it again to leach.
I use the Grow More urea free 20-10-20 with .05%copper, .1% iron, .05 manganese, .0005 molybdenum, .05 zinc.

Hope that's enough information. Thanks again for your thoughts and advice!

-Brandon

 

[Ray]

I fertilize at the aforementioned quarter strength every third watering. When not fertilizing I first give them a good soaking, and then go back through a couple minutes later and do it again to leach.
I use the Grow More urea free 20-10-20 with .05%copper, .1% iron, .05 manganese, .0005 molybdenum, .05 zinc.

Hope that's enough information.

No, it's not. "Quarter strength" of what? What we need to know is the mass of fertilizer per gallon, or the volume per gallon if you must, or even what the Grow More recommendation is so we can determine that for ourselves. Saying "it's a fraction" would be like going to a lumber yard and asking for a "short board".

 

[shade131]

Sorry, Ray. Thanks for your patience. They recommend one teaspoon per gallon. So, I use 1/4 tsp. every third watering. So that should be volume per gallon at least? The only other thing maybe worth mentioning is that the 20N is comprised of 8% ammoniacal nitrogen, 12% nitrate nitrogen.

That's all the information on the bottle. Hopefully that's sufficient, and thanks again.

 

[Ray]

WOW! Yet another example of how fertilizer manufacturers are trying to sell fertilizer, not help you grow better plants! And to think this one is also approved by the AOS (in return for financial consideration, no doubt).

A teaspoon per gallon of that formula would give you a 250-260 ppm N solution, ten times what I feed my plants. Your choice to use 1/4 of that was a good one, but at that concentration, I think your plants would do fine at being fed once per week.

 

[shade131]

That’s very helpful, thanks man! I’m moving to rain water, so if I understand correctly, this fertilizer lacks the calcium and magnesium usually found in tap water, so that’ll result in deficiencies, eventually. I’m either going to switch to k-lite or MSU. I may actually do both since I have a lot of duplicates, and try to otherwise control conditions and see where I’m at after a year.
Thanks again!

 

[Ray]

You can save yourself some money by mixing up the Grow More 50/50 with calcium nitrate, giving you a 17-5-10-9Ca blend.

Use that at 0.25-0.3 tsp/gal and add a teaspoon of Epsom Salt per gallon, and you're good.

 

[shade131]

Great idea. More money for plants!