IMHO the mix needs to be adjusted for each type of plant as no two plant groups are alike. The one size fits all method just doesn't work.
Yes, your method should work, as long as you do it every time. Vinegar breaks down in a week, and PH will be back to where it was. Mix gypsum or nothing (nothing is better) in the future with 5-1-1 instead of lime for acid plants. Research a new (to you) plant group in the future before you mix the soil for it.
I also disagree with the statement; "it is not such much the soil, but what you feed it with."
You can make adjustments sure, but vinegar is far from the ideal solution. Your plants are still going to suffer between feedings.
If the soil was right, they would not. No doubt you will see a difference in growth between a proper mix and the current mix. Even in a proper mix, you should not be using tap water without acid adjusting, so don't stop the vinegar once soil is adjusted. Or use rainwater. I myself store rainwater for the winter.

This post was edited by Drew51 on Sun, Dec 1, 13 at 11:34

Very sound advice. Thanks drew. I mixed without thinking it threw properly. Silly me...
I tested my rainwater (i'm in New Zealand) and it has a pH of 6.4. Still a bit high so I have to add the vinegar to that to. Is there a better acidifier to add than vinegar?

There are special plant foods for evergreens, hollies, and acid loving plants that can help lower the pH.

White vinegar might not be exactly 5% as it states on the bottle, which may mess with your precision from bottle to bottle. You can also use citric acid if you can find it.

Be careful with adding vinegar to water. A little of it can go a long way. If you add one liter of household vinegar (with a pH of 2.4) to 100 liters of neutral water(pH =7) it will result in a pH of around 4.

Wow, New Zealand! Hello from the great white north! I'm in Michigan, well not quite the great white north, but a lot closer than you!
What everybody else said is true too.
Ammonium sulfate is a super acidic fertilizer. But it may actually be too much! I would only use it 4 times a year a month apart, and only with active growth, 1 teaspoon to 2.5 gallons. You could put that in straight tap water.It will add sulfur to the soil, which will be converted to sulfuric acid by bacteria. Although not that well in pots. Even if not converted ammonium sulfate itself is super acidic and will lower PH immediately.
I guess our rainwater here is more acidic due to the factories. Tap water varies from region to region. Mine is 7.8.
The best thing to use for tap water is sulfuric acid. But it's dangerous, and you have to even be more cautious your PH reading is correct. Here it is available everywhere. You can buy it from Amazon. Same with ammonium sulfate and citric acid, Amazon sells all three.
Citric acid is a lot safer to use but expensive. It is also used in making preserves, so small amounts can be found where they sell pectin for jam.

In the orchards forum we had a long discussion about acidifying water and we found the research and all. And the only thing that worked to permanently lower ph was sulfuric acid. The problem with citric and vinegar (acetic acid) Is it will bind with bicarbonate, but bacteria will break down these acids and the bicarbonate is released and so the PH is only lowered temporarily. This does not happen with sulfuric acid. When this acid breaks down the sulfur is converted back to sulfuric acid by bacteria. So once the sulfur is there, it stays mostly as an acid. It can be flushed out, as can bicarbs.
You can easily obtain sulfuric acid, a weak solution is used for car batteries. So car battery acid is sulfuric acid, and most car parts places sell it. But the laboratory grade is stronger, and best to use. Well it is cheaper, and stronger. Battery acid is pure, and can be used.
Wear gloves and eye protection when mixing, and it is extremely poisonous . It must be treated as such. If it get's in your eye, you will lose your eye. Start by adding one drop or two, and measuring PH, it is a very strong acid, and a little goes a very long way.

This post was edited by Drew51 on Mon, Dec 2, 13 at 3:41

Thanks for the input everybody.
Drew. Interesting you talk about bacteria breaking down the acids. That's another thing I'm pondering on frequently. I don't think there is much bacteria in the 5-1-1 mix and even less if any in the gritty mix. I might be wrong but it just seems to me like a less than perfect environment for a little organism to make a living in. Another unknown that puzzles me is how does the use of chemical fertilizer, impact on the biological ecosystem in a container or in the ground for that matter? Any thoughts on that?

Bacteria do have a harder time living in pots but they are there. Ironic they seem to be everywhere we don't want them to be. If we removed everything from the world except bacteria, we would have an outline of everything still. Your body has 10 to the 6th power of cells, but it also has 10 to the 7th power of bacteria. Yes you carry more bacteria than you have cells in your body. Of course we could not live without them. So it's a good thing, they protect us actually.
Chemical fertilizers leave many salts in the soil. I don't know much about it as it is not my field of study in chemistry. I'm more a biochemistry guy. I do know it's not a good thing. Some do not just from looking at basic chemical structure. Both chemical and organic fertilizers deliver the same thing to the plants. In chemical it's pretty much already in a form that is useable. Organics need bacteria to break them down. They will break down in pots, but just not as fast as in ground. I like organic because they in general provide a constant stream of nutrients that can be used when needed. But it doesn't work well in pots. I use mostly chemical in pots. I'm still experimenting myself.
Most of my gardening is not in pots though. I have fruit trees, and grow blackberries, blueberries, currants, raspberries, and many other bush fruits in ground, or in raised beds. The raised beds are the very best with in ground action but yet like container culture. The best of both worlds. I can easily control PH, soil content, and moisture level in raised beds.
I feel each plant group is different and still experimenting with PH, soil content, and moisture levels for each group depending on what I want to achieve.
Of course I will always be experimenting it never ends. My oldest plants in pots are 39 years old.

This post was edited by Drew51 on Tue, Dec 3, 13 at 10:29

I wanted to add that once you start adding acids to your potting soil, you really need to monitor PH. Even though your rainwater is not as acidic as you like it will drive PH down. PH is a little more complex than what we talked about here. Depending on exactly what is making it basic, will determine how quickly and permanently it can be driven down. It's possible to flush bicarbs out of the soil too. Use vinegar to make bicarbs soluble, than leach with rainwater and many of the bicarbs now in soluble form will run out the bottom of the pot. Of course with lime, that will take many leaching sessions. The same can be done if soil is too acidic. Leaching the soil can drive the acid out too. Use tap water to do that.

Very interesting. Thanks Drew. If I want to monitor the pH properly then I need to get myself a more reliable tester. I have two but they are both cheapies that cant really be trusted. I realize pH is much more complicated but a proper tester will give a better indication. The Henna ones stands out above the others. Looks like I have to spend some serious money....!
Can you give me the link to the discussion about acidifying water in the orchids forum. I'm cross eyed from searching but cant seem to find it.

I could not find the thread either! I should have saved it. i did find some good for entertainment value!

Also I take back what I said about potting soil, how you water them, fertilizer, PH control is more important. You can change or influence the mix.
What Al says in general is excellent. It's a great guide, but for me just a starting point. One though I refer to often.

This is not the thread I was referring to, but is interesting all the same.

Here is a link that might be useful: Self taught chemistry

I grow cacti and found this info very useful

Here is a link that might be useful: Ammonium Nitrogen and Acidic Water for Xerophytic Plant Growth

WOW there is some very interesting reading. Thanks again Drew. I borrowed a post for everybody's interest as I think that explains it all.

"The real bad guy in the water is the bicarbonates not the alkalinity as the bicarbonates resist the acidic soils attempt in lowering the PH. If you use an organic acid like vinegar it drops the PH of the water but once the soil bacteria act on that vinegar the PH rises. With an acid like sulfuric it permanently removes the bicarbonates so it's acidifying effect on the soil is permanent. Like I said phosphoric acid will do the same thing, but at 10x the cost.

When I fill my 300 gallon tote I add an inch or so of water then pour in 3 cups of 33% sulfuric to it. 3 cups is what I need for 300 gallons for my well waters bicarbonate load, every water source would be different. It is kind of neat how it works because say I only add 2 cups of acid and fill the tote if I check the PH it would still be 7.2 which is my well waters native PH. It is like the first two cups is doing nothing but in fact it is removing the bicarbonates. You can actually see the process happen as it creates a thick layer of bubbles inside the tote. Once the bicarbonates are neutralized then and only then will the PH start to fall. I am not aiming for a very low PH just 5.5 or even 6 is fine. That is where your point of the blueberries doing fine in soil that is PH 6 comes in. They will do fine in soil of that PH if there is nothing in the soil or in the water used on them that is high in bicarbonates.

Lets look at rain water. Why is rain water so good for blueberries? Rain water has a PH of 7. Now that is way too high for blueberries right? So why is rainwater the best water source for BB with such a high PH? It has 0 bicarbonates. Basically when you use acid you are making your own rain water.....

It comes down to this. You could have PH 7.2 well water that is fine for BB while my PH 7.2 water is horrible for BB. It all depends on the amountg of bicarbonates in that water.

A real plus for me with so many plants is because I will acidify my water I don't have to add pelleted sulfur to the soil anymore and I also do not need to add pine bark. I would only use it at planting time then can mulch with anything I want to as the water will acidify the soil. A good way to view it is those with high bicarbonate water it is like you are pouring lime on your BB plants every time you water. It shows how important it is to not only have your waters PH tested but also the bicarbonate load."

My only concern now is the long-term effect on the container media. I guess the only way to be sure of that is to have it analysed by the laboratory. Its kind off expensive here so I'll do it once in the middle of summer and at the end of the growing cycle again.

The only thing I sort of disagree about is that vinegar or citric acid does make bicarbs soluble. So if you water a 2nd time very deeply maybe a few hours after the first watering, you can flush the bicarbs out of the pot. In other words remove them. At least this is my understanding of what happens when the bicarbs are neutralized they become soluble. I may be wrong, but I think that is correct.
Tap water is basic because of the bicarbs. Often it is added as acid corrodes pipes, so best to move alkaline water for long life pipes.
Eventually you should leach out all the lime in your pots. As long as you water deeply, some is flushed out each time. Of course how many your adding matters too!
In the other thread we found some data about aquariums, and they use phosphoric acid. The articles clearly states in a closed system vinegar and citric acid are useless. We though are not in a closed system. but was proof at least as far as us on the Orchard forum were concerned that acetic or citric acid did not really remove bicarbs long term.
This is more important in raised beds, or in ground, we need to remove them, as they cannot be leached out very well.
I just collected some more rainwater today. I will melt snow in the winter for my potted plants. I have enough now to get me through the winter with some supplements from snow. Luckily I try to limit water in the winter. Most of my plants are dormant. Only a few actually grow in the winter.
antidotal evidence but when I switched to rain water a few years ago, my plants grew like crazy, the deposits on the pots disappeared too. The difference was obvious.
If I run out of rainwater, I do have sulfuric acid. In the middle of summer, I cannot collect enough and use the acid on tap water.

This post was edited by Drew51 on Wed, Dec 4, 13 at 15:22

If you live in a dry place like I do and don't have too many pots inside, just use store-bought distilled water during winter (or any time of year I guess). This is what I do. I think I pay like .75/gal. Every time somebody in the family goes to the store (1x or 2x a week say), just automatically pick up a few bottles. This way you don't have to worry about adding acids, guessing amounts, pH readings, excessive flushing, bicarb build up etc etc.

The nominal cost is EASILY justified in my opinion. You can even make 50/50 mixtures with tap to stretch it out but then you'll get the bicarb/pH creep.

If it works for you, don't change it. It's a good option. I was a Medical Technologist and it beats working with the HIV virus, or super bugs resistant to antibiotics, or slide mounting human feces to see what worms you have, so for me it's just another day..

This post was edited by Drew51 on Wed, Dec 4, 13 at 18:55

Distilled water has a pH of 7.0 which puts me back to square one. My Azaleas shows chlorosis from a lack of nutrients (iron mostly) because of a basic pH I believe.
Most plants do good at a neutral pH but not Azaleas. I can see they are unhappy and I can only put that down to the pH.
I'm looking for sulphuric acid which is not easy to find in NZ. It all makes perfect sense and I have to say I'm very excited with this newly found knowledge and the following experiments. I will keep you updated Drew. A big thanks you to everybody involved.

It's not the pH of distilled water that matters, it's the zero alkalinity. Zero alkalinity means zero bicarbs/dissolved solids added (barring addition of liquid fert). Zero bicarbs mean lower pot medium pH (be careful of too low). Lower pot medium pH means happier azaleas.

And most potted plants do NOT do good (sic) at a neutral pH. The sweet spot for potted plants is around 5.8-6.4 pH.

Thanks for that Oxboy. We have a natural spring water station here in our town. The counsel made a beautiful landscaping feature of it. Its in the main street. About 10 water taps. People bring their buckets and plastic bottles and fill their drinking water for the week. In lean times I will take my 16gal containers and fill them there. (hope your hick ups is under control now)

That's cool.

Here in the states, "natural spring water" can be very different than distilled water. We embarrassingly have a million different types of water -- both naturally occuring and purchasable. The salt and mineral content can vary greatly so it always behooves the pot gardener to "know" as best they can the pH, alkalinity, TDS/EC and nutrient content of their irrigation water.

er..maybe 'pot gardener' wasn't the best way to put it. :)

Let's try 'potting enthusiast'...

The thing is in winter (when its not needed so much) we have an abundance of water. Last summer we had a drought. We weren't allowed to irrigate outside for 3mnths. That's very strange for NZ. Things are definitely changing. Its summer here now and the rain is slowing down again. I haven't got adequate storing tanks yet so I'll have to rely on tap water again. I don't really want to do that to my plants. I HAVE to find a way to improve this tap water as best I can so they don't suffer. Last summer they did not grow any and I can only put it down to that.
The counsel says the water ph is 8.0 and alkalinity is 25 CaCO3m3. To convert that to PPM is not that easy. Can you do that? Is that good or bad?
I have about 75 containers (mostly pre bonsai) in different sizes and the growth period here in NZ isn't that long so I have to get maximum growth while I can.

I found this in my local counsel's annual report. It just shows what chemicals are added to drinking water for human consumption. What's good for humans isn't necessary for plants.....

"This would mean reducing the alkalinity
and increasing the pH, which would reduce costs
by approximately $100,000, and reduce our
environmental footprint.
The corrosion potential of the water that we supply
is an important aspect of water quality. We adjust
alkalinity and pH which control the waterâÂÂs
corrosion potential using carbon dioxide, calcium
hydroxide and sodium hydroxide. This year, we
sought a better understanding of the effects, if any,
that our treated water has on pipes"