Alkaline water?

[Optimist]

What is the effect of Alkaline water on orchid roots. Would adding citric acid help. Would someone go through this on a newbie level? Thanks! Katy

[billc]

This might help you Katy.
Comprehensive Culture Guide—Watering orchids

Bill

[MrHappyRotter]

Depends on the pH and if the pH is high, what's causing it to be high.

High pH is usually caused by minerals in the water, such as calcium. If the water is very hard, you probably want to dilute it with very pure water (RO, distilled, rain, etc), which may not have a huge effect on the pH, but will definitely reduce TDS to more appropriate levels. If you have high pH, but otherwise low TDS / mineral content, then there's really no need to use any additives to reduce your pH, except in very specific cases when you're dealing with plants that are highly pH sensitive.

For the average home grower, however, as long as you've got a reasonable pH your plants will be fine.

[ALToronto]

pH alone is not the whole story - this point is not well emphasized in the article referenced by Bill. If you are serious about water quality, you need to get both a pH and a TDS (or EC) meters. Then you will find that at a high TDS, pH plays a much bigger role than at low TDS.

If you're using tap or well water, you will likely find that it's alkaline. Depending on the fertilizer you use, it alone may bring the pH down to an acceptable level.

However, if you use RO water and find that it's alkaline as well (mine reads over 8, at 10 ppm TDS), and you use an acidifying fertilizer, you may find the pH plummets to 5, because the water is so pure that the smallest shift in H and OH ions will have a major effect on the pH.

When the water is very pure, the actual pH reading is not very important. By the time you add fertilizer (and you should be keeping it to below 50 ppm of Nitrogen, I keep it at 20), you may find that instead of adding acid, you need to add some dolomite lime to bring the pH up.

Get the meters and play with the water and additives - see how the same quantities of fertilizer, acid and lime affect the TDS and pH readings of both pure and tap water.