Thank you Helpful1. I have spent quite a bit of time mulling over your
post. It contained a lot of information that I am not very familiar
with. I've had to do a lot of checking into things elsewhere. I'm
still left with many questions on points I still don't fully
understand.

I have a pH testing kit that only covers a pH range from 6.0 to 7.6. I
am looking into acquiring one of the electronic pH meters, probably
next week, after the holiday weekend. I'm finding it hard to justify
the need to quantify EC and TDS in my situation as a hobbyist
windowsill grower using city water. I am open to argument here.

I have flushed all my orchids both potted and mounted several times
now. I've noted that the water used for the flushes becomes more
acidic. After soaking as few as 6 pots in the 7 gal tub, the pH can
move from 7.6 to 7.0 and will continue to drop as more plants are
soaked in the tub. This may be due, in part, to the fact that I use a
lot of sphagnum moss in both my potting mix and on the mounted plants.
My assumption is that the moss should tend to acidify the water run
through it. I also wonder about the possibility of residual Phosphoric
Acid.

I have acquired a 20-20-20 fertilizer. I have applied it one time to
about 1/2 of my plants so far at a concentration of 1 tsp in 7 gal of
water, about 1/2 the recommended concentration.

Now, my water from the tap has a pH of 7.6 or more. I believe it is
published as 7.5. After adding the new fertilizer it jumps to 7.0,
neutral. Then after sitting several hours, it goes back to 7.6 or
higher. As the plants are soaked in the fertilizer solution the pH of
the solution drops and continues to drop off my presently limited
scale of 6.0.

From your post, I understand that the target pH for the fertilizer
solution is about 5.7. My first reaction was to question whether that
was too acid. Even though I cannot yet fully measure the pH, I am now
willing to accept that as a reasonable number from what trends I have
been able to see so far. Can anyone confirm or add an argument to
this?

Other things noted:

I've found more information concerning some of the symptoms I've noted
with my plants. I had assumed they were signs of fungal or bacterial
problems and treated them as such with little to no success.

My D.'s amethystoglossum, dearei, schuetzii and a few others were
plagued with blackening leaf tips that had a yellow band preceding it
as it progressed up the leaf. This also seems to be a classic symptom
of excessive Chlorine. These plants had not done as well for me as I
had expected.

Learning that in the D. amethystoglossum's habitat it grew on
limestone cliffs, I began adding dolomite a pinch at a time to the
surface of it's potting mix last fall and this spring. This season's
new growth is the largest and most vigorous growing shoot it has ever
put out for me. I am atributing that to the addition of the dolomite,
now to remove the Chlorine from it's diet by no longer using the fish
fertilizer.

Several others that I have treated continually for fungal and
bacterial problems over the last few years, and had come to the
conclusion that they were just "weak plants", are now candidates for
being helped to be better performers by adjusting their feeding. I was
almost ready to throw them out and acquire replacements. They've just
been reprieved for a while to see if this will help them do better.
Thx
S V





(Helpful 1) wrote in message . com...
Hello



High P is famous for inducing at least a severe Zn deficiency,
sometimes a triple Zn/Mn/Fe deficiency, very difficult to diagnose
visually. Zinc is essential to orchids, and most genus have Zn amounts
( foliar analysis) much higher than iron. Mn is usually pretty high
too.


The newer fertilizers with Calcium and Magnesium, usually coupled with
an high NO3 content induce a lot of micronutrient deficiencies. I can
see them in the analysis but they are not yet ver obvious visually...
Expect surprises similar to the CHC story, haydite, rockwhool and the
like in the coming years with those fertilizers.


Crystalline fertilizers are very difficult to store properly.
Micronutrients are usually gone by 3/4 to whole after only a year of
storage... Try to make a 30 x concentrate of your powdered fertilizer.
Usually there will be a lot of various crystals that will not
dissolve, easy to spot.



Quite common too... I have many orchid growers customers, not in the
USA.
Many of them are at a prehistoric age of growing orchids. I am sure
they would win at the lottery with the luck they have ! Most are still
trying to "improve" the growth of their plants, sometimes it works
sometimes not. Last people to talk is right. Sometimes it is possible
to undo their changes, sometimes not...

Substrate and macronutrient fertilizers needs at least a year, more
commonly 2 years to show any large problem. This group includes iron
too.

Micronutrients... it depends. Zinc and manganese is common today,
because many growers abandoned the old mancozeb fungicide several
years ago. Orchids have a quite high Zn content usually, and this
content slowly drops over the years if not properly supplied. Count
between 2 and 6 years for a plant to start funny yellow striping on
the leaves, and many new small growths on the plant.

Molybdenum deficiency is very common with the use of high NO3
fertilizers, but not yet a lot of obvious symptoms. Some plants here
and there in a crop are grayish, dull green, or yellowish. Usually
classified by the grower as "weak plants"...
It is translocatable, so expect a burst of weird looking plants in the
years to come. It is hard to diagnose, as the levels can be higher
than the recommended standard and still be deficient. NO3 (not total
N) foliar analysis is the only way to assess molybdenum deficiency.

Many growers are incredibly lucky. They will treat "leaf spot" with
mancozeb, and provide an additionnal Zn/Mn shot valid for a couple of
months or more, saving their plants. Sometimes they will forget to
correct the pH of the fertilizer once. Enough for the plant to restore
a part of its boron supply in an alkaline substrate. And so on...

Now, ask most growers. "Can you show me your foliar analysis ?" Have
you done any substrate analysis". A geranium grower will tell you
"yes". An orchid grower usually "wazzat ?"

Even a chlorosis of the new growth must be diagnosed by a lab... iron
deficiency exists, still many orchids suffer from iron toxicity, with
levels over 800-1000. This is what killed many plants grown in
haydite.

Iron-EDTA will sometimes exchange the iron against manganese (ans
zinc), and plants may improve with its use. This does not means that
iron was the culprit.


If you underfeed and use fish emulsion with an high Na content, you
may have a sodium toxicity. Dendrobiums have proven to be able to
replace a part of their potassium by sodium, during a potassium
shortage...

Basic :

- Mix 1 part of substrate to 1 and an half part of water, by weight.
Let stand overnight. Test the pH and EC. Optimum pH (according to
foliar analysis, and comprising all possible deficiencies and
toxicities of micronutrients) for SPENT medium is 5.7 for most hybrids
of most common orchid genus... Optimupm extract EC is over 400 and
under 1000 ( depending on the genus).
- Add some dolomitic limestone to raise the pH up to 6.

- Use a 20-20-20 (best one is the "20-20-20 Florida Special" from
Peters/Scotts) at the microsiemens rates given above, pH 5.7, no
more...
- pH of the substrate will drop using this fertilizer. Check the water
running out of the pot after a watering every other month. Too low,
add lime. Too high, use epsom salts once.

- Use from time to time a 15-5-15 CalMag or similar, but do not overdo
it. Once every moth to once every other month is more than enough.
Correct the pH to 5.7 too.

- You may use calcium nitrate and magnesium sulfate monthly , but I
have to know that those are more in excess than deficiency amonghst
the several dozen foliar and substrate samples I am doing yearly.
Magnesium sulfate - epsom salts - serves to supply SO4-, lacking in
many culture, and lowering the pH, therefore making micronutrients
available. Otherwise, the magnesium itself has no effet. IF you do not
believe it, use magnesium nitrate instead...

Good luck with your plants.