Do you adjust pH when watering?

[Ray]

A decent, calibrated pH meter is the best thing. Test strips are OK, but not particularly accurate, especially if they are old.

[IdahoOrchid]

Originally Posted by Ray

A decent, calibrated pH meter is the best thing.

Any suggestions on which and where to get one?

[Ross]

Originally Posted by IdahoOrchid

Any suggestions on which and where to get one?

I'd like to know as well. I just ordered this one CHECKER1 pH Meter - CHECKER1 which seemed cheap enough and seems to have pretty good specs, but I'm a real duffer on this stuff.

[IdahoOrchid]

I just saw that one on ebay for $23 plus 6 shipping.

[goodgollymissmolly]

you can buy a pH meter from any hydroponics store or web site. I would skip the cheaper ones sometimes referred to as "Pens". Get one with a pH probe wired to the meter. Milwaukee makes one for about $100. I've had mine for several years and it works well. It is best to store the tip of the probe in pure water or storage solution made for the purpose. It is not good to let the probe dry out. You can also buy an electrical conductance meter to match if you wish.

Now for a question...I know that the solubility of ions that plants need is optimized at about 6.0 pH. My collected rainwater is 6.9 which makes sense since it should be 7, but it dissolves some C02 which forms a weak acid (carbonic) while falling through the atmosphere.

It does not make sense to me that epiphytes need a pH of 6 (5.8 to 6.2) since the only water they get is fresh rain that certainly is closer to 7 than to 6. Where am I wrong here?

[Ross]

Originally Posted by goodgollymissmolly

It does not make sense to me that epiphytes need a pH of 6 (5.8 to 6.2) since the only water they get is fresh rain that certainly is closer to 7 than to 6. Where am I wrong here?

Same question I have - and where does RO water fall in here? What should be the pH of "pure water"?

[goodgollymissmolly]

Ross, the pH of "pure" water is 7.0. You can get that by distilling the water which is exactly what happens in the atmosphere. The water evaporates which removes all impurities including dissolved solids and dissolved gases. Then it condenses and rains pure water. Unfortunately it does not stay that way. It dissolves gases as it falls. One of them is CO2 which forms carbonic acid a weakly ionized acid. So the pH of rain is slightly below 7. If you live in the northeast where us rednecks send our smoke from coal fired electric plants then the rain also has dissolved SO2 and various nitrogen oxides that form strong acids. Rain in the NE can have a pH in the 5's. Not good.

If you distill water yourself the same thing happens unless you store it under an inert gas.

RO water is different. RO removes dissolved solids but not dissolved gases so its had to say what the pH of RO water is going to be. Depends on whats in it to start with.

The problem I have is that where orchids grow...at least the South American ones...the rain should be in the upper 6's so why do we think epiphytes need 6. I'm lost here somewhere.

[Ross]

Originally Posted by goodgollymissmolly

The problem I have is that where orchids grow...at least the South American ones...the rain should be in the upper 6's so why do we think epiphytes need 6. I'm lost here somewhere.

That's where I'm headed. What exactly is the target pH? I fully understand what happens with low vs high pH. That's not my question. My question may be same as yours - where are we with pH when we want to replicate "nature" for the spp involved?

[flhiker]

I collect the water from my window unit A/C and have tested the Ph at about 6.7 with a rapidtest meter. And my plants seem to be doing well.

[IdahoOrchid]

Originally Posted by goodgollymissmolly

The problem I have is that where orchids grow...at least the South American ones...the rain should be in the upper 6's so why do we think epiphytes need 6. I'm lost here somewhere.

That premise assumes that nature is perfect and maintains that pristine solution in the water. Just because the water is ph 7 (or very close) when it hits the branch does not mean that the nutrients are perfectly available to the plants it comes in contact with.

Also consider that the water must run along the branches and through the lichen, mosses and debris that exist on there as well. Water is absorbed and stored by these medium and I would bet the ph is affected to the acid side of the scale. Since the "pure" water is not totally absorbed immediately by the plant, I am willing to bet that the epiphytes see more of an acid environment that one would initially suspect.

Hey, maybe nature IS more perfect than I initially suspected!?!?!?!?!?