pH and fertilizers

[Sugar Magnolia]

After waiting forever to get a pH meter that works... then finding that the buffer solution wasn't included, then getting that too and calibrating my meter, I have come up with all sorts of numbers....

I am reading that orchids are good with 4.0-7.5, but the optimum levels are 5.5-6.5, so I'm shooting for 5.5-6.5. I got the meter because Ray (Thanks bunches!!) thought my fert may be too acidic. Here's what I got:
pH 6.2 - Distilled water (which I always use)
pH 8.3 - my tap water (yuck)

pH 4.3 - My fert in the distilled water.
pH 3.1 - (supposed to be 2.8) for Coke... had to try a known liquid that I had around.

So, here are my two questions...
1. Does 4.3 seem so low that that would be why one of my orchids looks like chemical burn?
and 2. Worm Tea... can you over fert with it? I feel like you can't, but that may just be why I am in this predicament in the first place. I have a couple gallons "brewing" now so I can't check it yet.

Thanksss!!
......aaaand now I read more on worm tea. Yea, not a fert. I always assume things are ferts. In that case, better alternative than fert, I guess??? I think I'm just so hung up on this pH issue now.

[Ron]

Hi.
The PH factor. AAAAAAAAHHHHHHHH.
It can drive you mad.
For a start what types of orchids are you growing.
The only plant I have ever had trouble with because of low PH was my Cymbidiums.
Causes by chemical fertilizers. they were 4.5.
In 8 inch pots I just threw 1/2 hand full of common garden lime of the top of the pot and watered in.
Solved the problem, they plants then grew on like a house on fire.

1. Does 4.3 seem so low that that would be why one of my orchids looks like chemical burn?

My chemical friend said it was far too low for the roots to react and take up the fertilizer, (Gues Ray B. perhaps could answer this better)

2. Worm Tea... can you over fert with it?

It is basically a tonic to me, I suppose used straight it could stuff up the Ph. and the plants ability to take up the food.!

Basically for my orchids, PH never seems a problem, unless fertilizer is used in excess
Cheerio
Ron

[rcb]

It's been a long time since I've done water chemistry, but if I'm remembering correctly distilled water is the "purest" water. It should be really close to 7 pH. So I would be a little suspect of the numbers you are receiving.

But if you are worried about the fertilized water being too low, an option is to blend in a little of the tap water to your fertilized water. Two reasons, the tap water has chemicals in it that will help buffer your fertilizer. And secondly tap water has minerals in it that are good for the plants ie Ca, Mg etc.

Maybe try a 9:1 and see what you get. If you are worried about Cl, just let the tap water sit a day in an open pot and the majority of the Cl will evaporate out.

[Andrew]

Originally Posted by rcb

It's been a long time since I've done water chemistry, but if I'm remembering correctly distilled water is the "purest" water. It should be really close to 7 pH. So I would be a little suspect of the numbers you are receiving.

Theoretically distilled water should have a pH of 7.0. In reality water dissolves gases, such as CO2, from the atmosphere until equilibrium is reached with the surrounding air. As distilled water has a low buffering capacity, the dissolved CO2 makes the water slightly acidic. pH 6.2 is around the range I'd expect for distilled water.

[rcb]

Andrew - yes that makes sense. Thanks for reminding me. We had our own closed distillation unit, so our water was extremely close to 7. For what we were doing, it had to be 7 in order for us to use it.

[Ray]

Actually, pure water, having absorbed CO2 from the air, can go as low as the mid-to low 5's. Fortunately, carbonic acid is a very weak acid, so its effect is completely overcome by anything else you put in the solution, so it's not worth worrying about.

As to the fertilizer solution, 4.3 is entirely too low; you should definitely adjust it to your 5.5-6.5 target range.

Sugar - what fertilizer are you using? Most "off-the-shelf" brands count on the buffering effect of dissolved solids in water supplies, so use the cheapest raw materials possible for their formulations, knowing that the pH will be OK. When those materials are added to pure, unbuffered water however, the pH typically plunges, just as you have seen. There are fertilizers available that are formulated specifically for use with pure water, so give you a good pH with no adjustment.

[11Orchid126]

I know mostly everybody raves about worm tea, but a friend in Missouri and I have both had bad experiences with it. My plants started looking poorly and she was losing plants left and right. Also, worm tea killed three of my most beautiful heucheras outdoors. We both stopped using it on a regular basis, and our plants slowly came back to normal. We only use it now once in a while as a tonic.

[Sugar Magnolia]

Originally Posted by Ron

Hi.
The PH factor. AAAAAAAAHHHHHHHH.
It can drive you mad.
For a start what types of orchids are you growing.
The only plant I have ever had trouble with because of low PH was my Cymbidiums.
Causes by chemical fertilizers. they were 4.5.
In 8 inch pots I just threw 1/2 hand full of common garden lime of the top of the pot and watered in.
Solved the problem, they plants then grew on like a house on fire.

My chemical friend said it was far too low for the roots to react and take up the fertilizer, (Gues Ray B. perhaps could answer this better)

It is basically a tonic to me, I suppose used straight it could stuff up the Ph. and the plants ability to take up the food.!

Basically for my orchids, PH never seems a problem, unless fertilizer is used in excess
Cheerio
Ron

Originally Posted by Ray

Actually, pure water, having absorbed CO2 from the air, can go as low as the mid-to low 5's. Fortunately, carbonic acid is a very weak acid, so its effect is completely overcome by anything else you put in the solution, so it's not worth worrying about.

As to the fertilizer solution, 4.3 is entirely too low; you should definitely adjust it to your 5.5-6.5 target range.

Sugar - what fertilizer are you using? Most "off-the-shelf" brands count on the buffering effect of dissolved solids in water supplies, so use the cheapest raw materials possible for their formulations, knowing that the pH will be OK. When those materials are added to pure, unbuffered water however, the pH typically plunges, just as you have seen. There are fertilizers available that are formulated specifically for use with pure water, so give you a good pH with no adjustment.

Geez...I've been MIA for quite a while, dunno if anyone will see this now.. anyhoo, my problem child is an Encyclia Cordigera and the fert is Better-Gro 20-14-13. I've since just diluted it further (what I had left in the gallon) and fed it to my hibiscus trees. I wonder now, if I use tap water, let it sit out a day, then add the fert, if the number would be about right. Maybe I'll try this weekend.
Ugh! Can I just hire someone to come over and set me straight with my orchids??!! Beer and pizza!! lol
Thanks for all the info!

[kmarch]

Originally Posted by Sugar Magnolia

Can I just hire someone to come over and set me straight with my orchids??!! Beer and pizza!! lol
Thanks for all the info!

Ok, I'll put in my 2 cents. Please don't take this the wrong way, I am genuinely trying to be helpful. I think you're way over thinking and analyzing this, making it much more complex and difficult than it is.

I have grown orchids for more than 13 years, have both fertilized regularly and not at all, have used tap water (3 different cities/2 different countries!!!) and rain water, and never once have I ever taken a pH measurement or even given any thought to it at all. Over the course of those years I have grown and flowered dozens of genera, have shown my orchids and have even won an AOS award for cultural excellence. All of this without paying the slightest bit of attention to pH. I also know growers both in the US and here in Australia who have been growing a lot longer than I have without ever taking a pH measurement.

I would recommend focusing on excellent culture/conditions and completely stop worrying about pH. Unless you're growing very picky, unusual orchids where such concerns become important, I'd put it out of your mind. Encyclia cordigera (NOTE: use a small "C" on the species name - species names are not capitalized) is not one of these unusual, picky orchids. I'd fertilize or not fertilize depending on how effective one seems to be over the other and enjoy the growing and flowering.

PS - As neither the beer nor the pizza will make it through customs, enjoy it in my absence.

[Ron]

Ok, I'll put in my 2 cents. Please don't take this the wrong way, I genuinely am trying to be helpful. I think you're way over thinking and analyzing this, making it much more complex and difficult than it is.

I have only once in the last 10 years checked my PH, that was for Cymbidiums and mainly because I had changed to a much stronger fertilizer.
I agree with Kevin, stop worrying and get on with enjoying growing orchids.
Make it a stress free enjoyable hobby.
Happy growing
Ron

[cym 1972]

i done an experiment with my meter yesterday out of curuoisity on worm liquid from worm farm.my ec meter came up between 6 and 7 on worm liquid in concentrated form.i hope this helps!