Water Quality: Hardness, pH, TDS. Where to draw the line?

[Roberta]

Originally Posted by emmajs243

I was pondering it tonight and decided that since I'm not positive, I'll check C&H's website to see if they specify and if not, I'll probably do like I would do with changing a dog food and bring it down to a more common range to start by mixing my well and RO water and try easing them up once they become acclimated to their new environment! That way, if I start seeing them not doing so well I can more easily pinpoint if it was the water or not. Or at least that's my hope!

I like the "dog food" analogy. I'm guessing that they either have very good local water or use RO, but they are a commercial nursery, giving their plants as close to optimal conditions as possible to optimize production, minimize losses, and provide aesthetic perfection to make happy customers.(They have been growing orchids for decades and are experts at the types in which they specialize) As a hobbyist, you would make yourself crazy and spend a lot of money trying to do that, and it's not necessary starting out. Orchids will adapt to less-than-ideal conditions (within limits... part of the fun of the hobby is finding out where those limits are)

[Optimist]

If you live in an area with lots of rain, you could think about gathering rain water. Rain water has 7.0 ph and TDS of 10 to 20 which gets lower the longer rain continues to pour. Many people collect rainwater in a rain barrel. I live in the desert and the tap water here comes from the Ogallala aquifer, but I use rain barrels to collect rainwater although I am able to use the rainwater for only a short time during the monsoon seasons, it certainly lowers the yearly cost of water for orchids.

[King_of_orchid_growing:)]

TDS of the water will usually not be a significant factor until you start getting into orchids that are more sensitive to high amounts of calcium carbonate in the water such as Pleurothallids or Disa. Even then, TDS in and of itself as a parameter is kind of useless. It is too broad of a parameter. It only tells you the amount of dissolved solids present in the water, it does not tell you what kinds of dissolved solids are in there and in what concentrations those specific minerals are at. People usually assume it is mostly calcium carbonate or calcium bicarbonate, but the TDS reading can capture pretty much other minerals dissolved in the water as well.

Many of the commercially available orchids that are sold to the majority of orchid growers are generally very tolerant of less than ideal water quality.

I would stay away from using water conditioners though.

RO/DI and rainwater will usually fit the bill just fine. TDS does not have to be 0 ppm even for the sensitive orchids. The plants still need the nutrients present in water in trace amounts to metabolize.

Of particular importance are the nutrients calcium, magnesium, iron, and zinc among some. Again, trace amounts are fine, excessive amounts can be highly toxic to the plants.

[Orchid Whisperer]

Originally Posted by King_of_orchid_growing:)

TDS of the water will usually not be a significant factor until you start getting into orchids that are more sensitive to high amounts of calcium carbonate in the water such as Pleurothallids or Disa.

I would agree, if you have a good idea what constituents make up the dissolved solids. If you are in a coastal region, or in the gulf coast area where salt domes are common and can affect well water quality, then sodium may be a significant problem, and more of an issue for orchid health. If I lived in northwest Georgia, or parts of up-state North Carolina where limestone is common, then the TDS could be elevated due to calcium carbonate, but not be a concern for most orchids.