Can I use my tap water for daily watering and fertilizing?

[Ray]

Originally Posted by MateoinLosAngeles

Using RO or not is really location dependent.

Actually, it is, as your NY versus LA examples demonstrated.

Many orchids evolved living off of extremely pure water into which minuscule amounts of nutrients were dissolved. Their diet is supplemented by microbial-, and host tree exudates and the occasional bird dropping or the like. Rupicolous species, whose roots grow into the organic-rich cracks and fissures in the rocks, may benefit from addition minerals from them, but most rock isn't all that water soluble, so that isn't much.

"Purity" of the water (how much is dissolved in it) goes hand-in-hand with "what" is in it, and its other chemical properties.

NYC water is typically no more than about 50 ppm TDS, which is certainly pure enough for essentially any orchid.
I think it is doubtful that you have any noticeable difference in you plants from those using totally pure water.

My water here in coastal North Carolina contains only slightly more mineral than that - mostly sulfur - and then is "sweetened" with lime, adding about 50 ppm Ca. I can discern no difference between plants grown with that and plants grown with RO.

When I lived in KY, mt water was almost "liquid cement", and while plants like phals and paphs tolerated it well, their leaves were very dull in appearance.

The bottom line is that you should get you water analyzed before making any decisions about using your tap water.

[MateoinLosAngeles]

Attachment 161136[/QUOTE]

Originally Posted by Ray

Actually, it is, as your NY versus LA examples demonstrated.

I probably should've used commas for a clearer read. I meant to say that "Using RO, or not, is location dependent"

[itilien]

Thank you all very much for the replies.

There is one question left unanswered. Since I don't grow in semi hydroponic, and my plants dry out between two waterings, will there be a build up of minerals if I add fertilizer to the daily water, no matter RO or tap?

And some others - If I decide to try to make my own fertilizer, what can I use to increase the N without increasing K and Ca? Maybe ammonium nitrate? What can be used for a source of P? And are the micro and trace elements in my tap water enough, or they need to be bumped too?

[Clawhammer]

I fertilize with every watering. When my fert reservoir empties I flush with plain water for a week before refilling. I also don't fertilize in Nov-Dec. No buildup.

[itilien]

Clawhammer what concentration do you use and what are the orchids?

[Clawhammer]

Originally Posted by itilien

Clawhammer what concentration do you use and what are the orchids?

25ppm nitrogen. My water is similar to yours.

I have like 600+ orchids across most genera. I've never encountered an issue because of water purity.

If you are extremely buildup adverse maybe avoid clay/terra cotta pots, but otherwise you will be fine.

[Ray]

Originally Posted by itilien

There is one question left unanswered. Since I don't grow in semi hydroponic, and my plants dry out between two waterings, will there be a build up of minerals if I add fertilizer to the daily water, no matter RO or tap?

100% of the time, if the solvent (water) evaporates from a solution, the solute (dissolved minerals) will precipitate, becoming "mineral buildup". Once deposited they are very slow to redissolve. The greater the concentration of dissolved mineral, the more buildup will occur.

Originally Posted by itilien

If I decide to try to make my own fertilizer, what can I use to increase the N without increasing K and Ca? Maybe ammonium nitrate? What can be used for a source of P? And are the micro and trace elements in my tap water enough, or they need to be bumped too?

I suggest that you just buy a decent commercial fertilizer and use it regularly and sparingly. With a formula like Akerne's Rain Mix, the plants will get everything they need and any elemental excesses are not enough to cause any harm.

Fertilizer is very low in orchids' "Maslow's Hierarchy of Needs". Your growing efforts will be far better rewarded by focusing your efforts on the many other cultural parameters.

[itilien]

At the moment I have Orchid Focus Grow, which is formulated for soft/rain water and has 1.8:1.2:2.1: 1,72 Ca, magnesium is not specified. I use it with concentration 1.5ml/L of water once per 10-15 days. Maybe I can modify my misting system to use water with fertilizer every second or third day, and to use pure water in the rest.

I know that fertilizing is not the most important part and I don't put my effort only on it.

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[Ray]

Originally Posted by itilien

At the moment I have Orchid Focus Grow, which is formulated for soft/rain water and has 1.8:1.2:2.1: 1,72 Ca, magnesium is not specified. I use it with concentration 1.5ml/L of water once per 10-15 days. Maybe I can modify my misting system to use water with fertilizer every second or third day, and to use pure water in the rest.

I recommend using a 100 ppm N solution weekly. At 1.5 ml/L, you're only applying a 32 ppm N solution far less frequently. I recommend "upping" it.

As it is not listed, it may not contain magnesium, but that's easy enough to remedy - once a month, irrigate your plants with an Epsom Salt (MgSO4-7H2O) solution of about 1.5-2 ml/L. The plants will store it and move it to newly-growing tissues as needed.

[MateoinLosAngeles]

Originally Posted by itilien

I know that fertilizing is not the most important part and I don't put my effort only on it.

Based on the quality of your water and everything you've described about your watering habits, I think you might be a good candidate for slow release fertilizers and don't worry about mixing when watering. If you do have access to RO water or Distilled, then you can use that for the misting system only, which will prevent most deposit from forming, and keep watering with your good quality tap water.

You can use the slow release as a "baseline," assuming that your water analysis works in a range and is not necessarily going to be ever consistent. If you want to be safe you can aim for 75ppm N a week with a slow release and then adjust from there based on observation.

Ray has some good stuff on the topic:
Slow Release Fertilizer › First Rays LLC
Osmocote Pro Controlled-Release Fertilizer - 2 Lb › First Rays LLC

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