pH level of water

[BillC]

Is it an essential requirement that water should have a pH level of 5.5 / 6.0 for orchids? I know it is recommended, but if one has only tap water should acid be added to the water to lower the pH value before use?

[Cynthia, Prescott, AZ]

No, this is not required. If you have a PH of around 8 or higher, you would need to leach the mix very often to prevent calcium salt build up in the pot. I sometimes added phosphoric acid to my water with a siphon to reach about 6 to 6.5 PH, to help leach out the salts. But in 25 years of growing, this was only done regularly for a couple of years. The rest of the time, I just made sure that a lot of water was used(~8 PH), and the plants did just fine. Much more important for me now is that I am using Canadian peat in my mix which gets quite acid, sometimes down to 4.5 PH. I have seen a bit of stunting in some of my plants, and am working on an additive to bring the PH up to about 6.5. I suspect that in general, the mix has a bigger PH effect than the water. Cynthia

You should test the ph of your water before and after adding fertilizer as it can change the ph.

[BillC]

Cynthia, thanks for the advice; I shall not bother to be too concerned about the pH value of the water in future.

[Cynthia, Prescott, AZ]

126 is right about fetilizer. Most fertilizer manufacturers assume the average person will be using moderately hard water with a slightly basic (7+) PH, so they formulate the fertilizer to bring the PH down. This can represent a problem for people using RO water, as it can go very low in PH when the fertilizer is added. I use RO water, and always add about 20 to 30% of my tap water when I use a fertilizer that is not manufactured specifically for pure water. Cynthia