Brown aerial root tips on Brassavola

[j_orchids]

Originally Posted by estación seca

You water TDS are great for almost all orchids. You can use small amounts of fertilizer intended for pure water with your tap water when fertilizing. ....

If you use a fertilizer with Ca and Mg and correct your pH you probably will not need to supplement.

Are you suggesting the my TDS may still be a little but too low to provide the needed Ca and Mg, and I should suppliment with a little "pure water" fertilizer that contains these elements? Are you suggesting a mix of "pure water" fert. with the "tapwater" fert. that I have now and mixing that with my tapwater or are you suggesting a switch to 100% pure water fert. and mixing that with my tapwater?

Thanks!

~ Jon

Oh, PS - I'll check and adjust the pH. is pH 6.0 considered ideal?

[estación seca]

Fertilizing isn't that critical, so worry more about providing proper light, water, humidity and temperature.

If you want me to be specific... because there are a lot of ways to do things....

Unless you grow Phrags and cloud forest miniatures, I would use your tap water with a fertilizer formulated for pure water. I wouldn't bother with distilled nor RO water. I don't think it's worth the expense, given your tap water.

If I intended to use a low level of fertilizer with each watering, I would aim for 20-30 ppm of nitrogen in the final solution.

If I intended to water with plain water most of the time, and fertilize every now and then, I would use a higher concentration of fertilizer on the days I do water. How much to use is up to how your plants are growing, so I can't predict.

I would check the pH of the final fertilizer solution and adjust as needed to a pH of about 6.0. That is good enough. Ideal pH is impossible to determine because it will vary with ambient growing conditions, nutrient levels and growth stage.

I would also adjust the pH of your tap water to 6.0 when using it without fertilizer. Any calcium and magnesium in your tap water are unavailable at your pH.

You said your fertilizer lacks calcium and magnesium. In that case I would get a Cal-Mag supplement and use it. I haven't used such a supplement because my fertilizer has Ca and Mg and when I do a flush watering I often add a little tap water to rain water.

You can find out how to dilute fertilizer to target ppm nitrogen, and read a lot more about fertilizing, if you go to the First Rays Web site and click on Free Information.

[j_orchids]

Originally Posted by estación seca

Fertilizing isn't that critical, so worry more about providing proper light, water, humidity and temperature.

If you want me to be specific...

It couldn't be more clear now! I see what you have been driving at all along. I'll adjust my pH and look at getting a Ca-Mg suppliment or switching to a "pure-water" fertilizer. Thank you so much for all your help!!!

~Jon

[Roberta]

The regular fertilizer (not the pure water formulation) should nicely adjust the pH down to the ideal range, especially with your low TDS. You're using it a perfect low level, so it probably isn't over-correcting, but testing would be a good idea (you can make any "tweaks" a lot better if you know what you're working with to start) I'm pretty sure the pure-water formulation does not provide much acidification,, since pure water tends to be on the acid side from dissolved CO2. That is why your regular Peters formulation is probably just fine with the tap water and you then shouldn't have to add calcium or magnesium (don't raise the TDS unless there is is a good reason to do so... knowledge is power)

[j_orchids]

Originally Posted by Roberta

The regular fertilizer (not the pure water formulation) should nicely adjust the pH down to the ideal range, especially with your low TDS.

Right, I'll check and adjust pH of my fert. water after adding the fert., and I'll also check and adjust pH of any water I use for flushing. Thanks!

~Jon

[Roberta]

Originally Posted by j_orchids

Right, I'll check and adjust pH of my fert. water after adding the fert., and I'll also check and adjust pH of any water I use for flushing. Thanks!

~Jon

You may be over-thinking this. Cattleya-tribe orchids are quite tolerant of a range of conditions. Sudden changes are more of a problem than any specific set of conditions. For instance, mine do just fine on tap water with a TDS of about 300 and a pH of about 8. Fertilizer adjusts the pH down a bit (I add a little vinegar, too, to get it down to maybe 6.8 but they get any fertilizer at all maybe once a week or maybe I go two...) Your water out of the tap is MUCH better than mine. You don't have to work hard to improve it.

[bethmarie]

Sometimes it's fun to be more exacting, sometimes simple is good. So for what it's worth, I experienced the same with my brassavola when I was underwatering. If you feel like the potted roots are getting plenty of water, I think estacion's suggestion will solve your problem--just mist the aerial roots in between watering the pot.

[j_orchids]

Originally Posted by Roberta

You may be over-thinking this.

Originally Posted by bethmarie

Sometimes it's fun to be more exacting

I'm sure both are true. I'm a scientist and cartographer, so I am a bit obsessed with data and precision.

I discovered something new today:
My water tested right out of the tap at pH 8.5 as expected by the data published by my utility, but running that water through my filter then testing it yielded pH 7.0. I looked up manufacturer's spec on the filter, thinking it was only certified to remove chlorine along with a few heavy metals, VOCs, and pesticides, and I discovered that it is also certified to reduce Carbonate Hardness (CaCO3). That explains the drop in pH with filtering. I also looked up my utility's 2015 annual report, which reports on more parameters, and discovered that the harness of my water is due almost entirely to carbonate hardness (they reported only 1ppm of sulfate). Based on this, it seems there is probably very little usable Ca or Mg that can be provided to my plants regardless if I filter my tapwater or adjust it's pH.

It sounds like the optimal solution is to add some RO-specific ferilizer to my filtered tapwater, and then adjust it's pH for general use ...and to use filtered tapwater (no pH adjustment probably needed) for periodic flushing.

Again, probably over-thinking, but...

~ Jon

[Roberta]

Another thought... just use your Peters formula (which will probably take care of dropping the pH of the tap water, also making the calcium and magnesium available. If the hardness is calcium carbonate (most likely) then a small pH shift a shade below 7, which the tap water fertilizer will do, takes care of everything in one fell swoop. Your TDS is low enough that you don't need a whole lot of phosphate (the middle fertilizer number) to put the pH right where you want it.

[Prashant]

Is the Brassavola nodosa bloom in specific time of year? If not what will be the light requirements and is it do well in artificial light conditions?