contagious rot in Cattleya new growth

[Oranagra]

it takes nearly 2 hours to soak my 40 orchids for 20 minutes each (in decorative post, in groups). so i water once a week (weekend, morning), or once in two weeks in winter.
and then i supplement the ones that dry faster, or need to be kept moist by spraying water on the top dressing every couple of days, when needed.

but since i started using the bamboo stick method, i notice that the stick seem to feel moist, even though the media looks dry (light brown), so i may have been watering too much.

anyway, regarding calcium, i can try to add some supplements, or change my fertilizer.
but i wonder, maybe it's a mistake to use rain water and air-conditioner condensation water?

[camille1585]

Some one else here had posted about using air conditioner water, and although I don't remember the details of the discussion, the answer was that it was generally fine to use that water.

There is no problem with using pure sources of water, but fertilization has to be adapted to it, since it contains few to no nutrients. Using a complete fertilizer with also calcium, magnesium and trace elements is a good idea to avoid deficiencies. Standard fertilizers which supplement only NPK are fine with tap water, since tap water usually contains enough of the other (trace) elements.

In Israel are you able to find any fertilizers specificially designed for pure water? They're easy to find in North America and Europe, but not sure about everywhere else. Otherwise try to find a supplement of Ca and Mg, and you can consider periodically watering with tap water to give the plants any other missing nutrients.

[Ray]

I am going to be a "nay-sayer" again on the calcium deficiency.

As it grows, all plant tissue needs a steady supply of calcium. Unlike most other nutrients, calcium is not well transported within the plant - once absorbed and used, it is "locked down" - so old tissues cannot supply it to newly-growing ones.

That being the case, the classic symptom of calcium deficiency is the blackening (death) of new growths as they emerge from the plant. In these photos, it is apparently that they grew fine and then contracted an issue. This could only be a calcium deficiency if it had been adequately supplied, and then stopped altogether when the growths were partially mature.

[SundayGardener]

I also have this problem with my cattleyas. Or perhaps two problems. One is that the new growths have new leaves coming out that are black. The other is overall blackening of leaves.

There should be plenty of calcium in my water, since I switched to tap water for the catts and we have hard water with a lot of lime. I also added oyster shell as a top dressing to the pots. In two cases, adding additional calcium did resolve the issue, and the leaves went back to a normal color.

I really doubt that I am overwatering in the sense of watering too frequently, since typically I am advised that I am underwatering. However, I may be overwatering in the sense of providing too much water at the times when I do water. Depending on a given plant's schedule, like the original poster, I will water once a week, and I might let the plant soak. I tend not to do this in the winter because it doesn't work well, especially not for catts, which I don't let sit in water for longer than 10 minutes. It is convenient for me though, because it takes longer to repeatedly drench a plant one by one. With soaking, I can have multiple plants in their respective private tubs, then drain them and it's usually more efficient (for me, maybe not great for the plants). When I don't soak, I drench, which is what is usually recommended--to imitate rainfall. But I find it hard to water from the top without spashing and getting leaves wet. In any case, I have noticed that I have symptoms of plants getting too much water at one time--a variation of overwatering?

Then there is what looks like brown spot, but it doesn't respond to the recommended treatments. So it is frustrating, for sure. I cleared and wiped down an entire shelf with Physan to disinfect the growing area, but it's about guaranteed that any plant that I put on that shelf will develop spots, typically on the youngest growths.

Not to derail, just saying that I have tried bumping calcium with some success, have switched water and changed up how I water, and continue to seek answers. Also, I have several catts that receive the same care as the others and are located on the "danger shelf" and have absolutely no problems whatsoever.

[Orchid Whisperer]

Originally Posted by Ray

I am going to be a "nay-sayer" again on the calcium deficiency.

As it grows, all plant tissue needs a steady supply of calcium. Unlike most other nutrients, calcium is not well transported within the plant - once absorbed and used, it is "locked down" - so old tissues cannot supply it to newly-growing ones.

That being the case, the classic symptom of calcium deficiency is the blackening (death) of new growths as they emerge from the plant. In these photos, it is apparently that they grew fine and then contracted an issue. This could only be a calcium deficiency if it had been adequately supplied, and then stopped altogether when the growths were partially mature.

Wrong again.

This evening I will post a presentation given this past weekend at the Northeast Georgia Orchid Society. Not my presentation, but one developed by one of our members (professional horticulturalist, master's degree). A part of his presentation focused on Ca deficiency, the symptoms look like the OPs problem. Could easily be caused by very high puriity water, lacking Ca. Easily corrected.

Before we go there . . . not caused by too much K either.

[Ray]

Originally Posted by Orchid Whisperer

Wrong again.

Now THAT made me laugh out loud!

[Roberta]

Originally Posted by Oranagra

it takes nearly 2 hours to soak my 40 orchids for 20 minutes each (in decorative post, in groups). so i water once a week (weekend, morning), or once in two weeks in winter.
and then i supplement the ones that dry faster, or need to be kept moist by spraying water on the top dressing every couple of days, when needed.

The first thing that jumps out at me is the "soak" part... if multiple plants are soaking in the same water, it it very likely that any infection that one plant has is being spread to the others that share the water. (You don't share your toothbrush, multiple plants shouldn't share the same water) Instead of that long soak you (and your plants) would be much better served by letting water run through the media. This not only flushes out salts, rot, and other crud, but also pulls air into the root zone (something that most orchids, and especially Catts, want and need) Back in the days when I had plants living in the house, I used plastic bins (deep trays) under them, and underneath I used the plastic light-diffuser with holes (we call it "egg crate", holes are around 1 cm square). If that isn't available, any sort of inexpensive wire shelving works well too. (Anything that permits drainage and air exchange) You can't water an orchid too MUCH, you CAN water it too OFTEN.

Where the thin membrane on the outside of the pseudobulbs or the sheath, turns black, you often can gently peel it away (if it is separate from the tissue underneath and comes loose easily - don't remove it if it is firmly attached!) That lets things dry out and especially where there are buds, possibly prevent rot from developing in those)

If you think that you may be using water that is too pure, consider watering with half tap water and half pure (like AC) water mixed together if your tap water is very high in solids. But I have found that Catts are really not very fussy about water quality, especially compared to some of the thin-leaved orchids. Mine are quite happy with water that ranges from 250 - 350 parts per million total dissolved solids (most of that is calcium carbonate) and I have friends who have water that is considerably worse, who still quite successfully grow them.

[Oranagra]

Thanks Roberta.

I actually don't share water.
i put each plastic post in a decorative ceramic pot, fill it with water, let it soak for 20 minutes, and then dump the water, then do the same for another plant (using the same decorative pot, but not the water).

I do the soaking only in the summer, so that the bark chips really absorb the water and stay moist for longer.
I think that (especially with new bark chips, in the first few months after repot), just running water through the media doesn't seem to wet them enough, and they'll be bone dry within hours.

once in a month or two, i flush with clean (non fertilized water), but, in summer i do this flush by soaking, and in winter, i do it by running water through the pot.

also, if i water (or flush) by running water though the pot, then i can't afford to run a lot of water, since i don't have that much A/C / rain water to spare (it would also be wasteful in fertilizer).. i.e. i can't pour 2 liter of water on each plant. soaking is more economical.

I just tested the total dissolved solids of my tap water with a cheap TDS meter from Ebay, and it showed 150 PPM (i seem to remember much higher numbers in the past).
Then i called the person responsible for the water supply in my settlement, and he said that there should be around 250 PPM (my meter is probably off).
so maybe it is better for me to stop playing with rain / A/C water and just use tap water (in which case, maybe my un-rated fertilizer is ok). what do you think?

[Roberta]

Either way, your tap water should be fine for Cattleyas. Then the fertilizer should be fine (half the strength that it says on the package) And Catts really do need to dry out between waterings. I grow mine mostly in baskets (and mostly outside) so they are pretty dry a few hours after they are watered. In the hottest part of summer they get watered every two to three days, in winter more like once a week. So they have a significant period where they are quite dry. But if you use tap water, you can run it through the pot with no worries. (If you need to save the water, you can run it into a bucket and use it on garden plants... ) If you have room to grow outside, those Catts will thank you. (I think your climate is rather similar to mine... depending on exactly where you live, winters may be a little colder and of course you do need to bring them in if there is frost, but outside as much as possible is ideal)

[Oranagra]

I managed to get a hold of an official test result of my tap water.
I'm not sure i'm reading it correctly, but it looks to me that the TDS is about 1000 PPM.
Or am i supposed to look only at Chloride (which is about 300 PPM)?

Anyway, assuming my Catts, Phals, and Den.Pahls can handle it.
I wonder if there are any other orchid groups that will not tolerate that soup?
I have Vandas, Oncidiums, Bulbophyllum, Paphiopedilum, Cycnodes, Den.Nobli. (full list in my profile)

General nitrogen (MERCK) 9 mg/L
Ammoniacal nitrogen (MERCK) 1.9 mg/L
Kjeldahl nitrogen (computed) 1.96 mg/L
Potassium-AA < 5.00 mg/L
calcium* 163 mg/L
magnesium 49 mg/L
Boron 0.07 mg/L
Sodium-AA 93 mg/L
Bicarbonate 390 mg/L
Chloride (Cl in IC) 291 mg/L
Nitrate (N in IC) 6.85 mg/L
Nitrite (N in IC) 0.19 mg/L