Water pH levels suitable for orchids

[Guillaume]

Hi, the revers osmosis water that I use on my orchids has a pH of 8.4. I was under the impression that water with a low concetration of disolved salts should be closer to 7. Is this high pH a problem?

[DavidCampen]

Originally Posted by Guillaume

Hi, the revers osmosis water that I use on my orchids has a pH of 8.4. I was under the impression that water with a low concetration of disolved salts should be closer to 7. Is this high pH a problem?

The pH of purified water is a meaningless metric. If you don't like the pH of a sample of purified water then add a _tiny_ amount of acid or base and change the pH to some other value.

Do you water your plants with pure RO water and if so, why?

Edit:
If you want to change the pH of your RO water from 8 to 5 then add a drop or two of vineger to each liter. But again, this would be meaningless since just a tiny bit of bicarbonate would bring it back to pH 8.

You should measure the pH after you have added the nutrients that you normally use when you water then the pH value will have some significance.

[Guillaume]

I have been using tap water, but our municipal water is not very "safe". I find that a lot of new root growth end in the growing tip dying off, and so recently started using RO water. It has not been long enough for me to see if this helps though. I'm happy to hear that the pH has no real baring on the 'orchid friendliness" of the water. Could there be another reason for the growth tips dying off?

[DavidCampen]

Originally Posted by Guillaume

I have been using tap water, but our municipal water is not very "safe". I find that a lot of new root growth end in the growing tip dying off, and so recently started using RO water. It has not been long enough for me to see if this helps though. I'm happy to hear that the pH has no real baring on the 'orchid friendliness" of the water. Could there be another reason for the growth tips dying off?

You should post photos.

[PaphMadMan]

Originally Posted by Guillaume

I have been using tap water, but our municipal water is not very "safe". I find that a lot of new root growth end in the growing tip dying off, and so recently started using RO water. It has not been long enough for me to see if this helps though. I'm happy to hear that the pH has no real baring on the 'orchid friendliness" of the water. Could there be another reason for the growth tips dying off?

Your tap water could be the cause of the root tip problem you describe. Build up of salts from hard water can make a harsh environment for sensitive root tips.

pH of very pure water, like RO water, is of little concern. It changes easily and quickly when you add fertlizer or it comes into contact with naturally acidic organic media. In hard tap water pH is a big concern because it does not change easily, and you do want slightly acidic conditions for most orchids, for best availablility of most nutrients.

[Guillaume]

I'm in South Africa and our water is hard and alkaline. Our town water is of poor quality and I think the municipality adds a lot of chemicals to improve the safety of the water. Our spesialist orchid nurseries use bore hole water, which would also be hard, with no serious effects. I will post a few pics when I get back this afternoon.