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This clinic is an example of the pour through method of pH testing for orchid media. We
have some Phalaenopsis
which have been in their mix through the growing season, roughly for about 8 months. Their bloom spikes are
nearing maturity and the plant will soon be in bloom. Two of these Phals are in Phal
Monterey Imperial Orchid Mix and one is in Phalaenopsis Gold
Classic Orchid Mix.
We know that the pH of orchid mixes changes over time. We would like to have our Phals
in media with a pH that is
between 5.5 and 6.0 which allows the plants to best use fertilizer for
strong root development, plant strength, and healthy spikes with good flowering. Since we won't repot these
Phals until they go out of bloom we want to test the media now.
First we gather together the supplies that we need. We have a small glass of RO water
(bottled water), pH test strips, a
clean clear plastic saucer, and an orchid which was watered a little while ago so its media is nice and damp. We
want to be especially careful not to throw off our test by using a collection container that has any kind of
residue in it.
We measure the pH of the water by dipping a piece of pH test strip into it. We then
tape the strip to the
orchid's ceramic pot just to hold it while we perform the other steps. We don't want to set it down on our
counter top because we don't want the damp strip to pick up any residue from soap, etc that may be on that
Next we pour a small amount (2-3 ounces) of the water through the pot and allow it to
drip out the bottom holes
into the saucer. This water, called the leachate, is what we will measure the pH of. Its pH will have been
affected by contact with the media in the pot.
We measure the pH of the leachate with another new strip of pH test paper. We then hang
that piece on the ceramic
orchid pot next to the other one.
After orchid mix has been in a pot with an orchid for a while there is a lot happening
that can have an effect on
the pH of the orchid mix. The orchid mix breaks down over time and that causes changes in pH. That is one reason
repotting is so important for these beautiful plants. Additionally, as fertilizer and water are regularly added
to the mix, they have their own pH and will interact with the media which alters the pH.
For comparison we take another strip of pH test paper and use it to test our tap water.
We prefer to use pure
water, either RO or distilled, for leachate testing as it has less buffering and will provide us with a better
estimation of pH when poured through the pot.
The RO water by itself tests at about 4.5.
The tap water tests between 5.5 and 6.0
The leachate tests at about 5.0
Since we want our Phals to be in media that is between 5.5 and 6.0 we are going to top
dress this plant with some
pellets of dolomitic lime. If the pH
had been too high we would consider using Citric Acid in our
For more information on pH and testing see our pH Test Strips.
“This fall I religiously followed your advice, creating an environment of shortened
days and lower temps in order to encourage blooming...I was successful. FINALLY!! Thank you, thank you!!
Both of my plants decided to bloom and they look beautiful. I wanted to share the good news and
my gratitude with you. Thanks again!”Laurie J.
“The potting medium you sent is gorgeous!! It's superior to the bark I've been
buying at Lowe's. I can't imagine what (my orchids) will do when I put them in your potting mix. It even
smells fresh!! Many, many thanks. I'll be ordering from you again.”
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