FW: Tap Water

From: Malouf, Perry (Perry.Malouf@jhuapl.edu)
Date: Thu Dec 16 1999 - 11:40:55 PST

Date: Thu, 16 Dec 1999 14:40:55 -0500
From: "Malouf, Perry" <Perry.Malouf@jhuapl.edu>
To: cp@opus.hpl.hp.com
Message-Id: <aabcdefg4160$foo@default>
Subject: FW: Tap Water

Michael Catalani wrote:

>....I have used water straight from the tap here in Memphis for
> more than 25 years to water just about every type of cp. ...I dont
> even let the water sit for a few days to burn off the chlorine. I have
> absolutely no problem with salt buildup, chlorine, or other
> minerals. .....I believe there are three types of tap water; the
> type that can be used immediately, the type that needs to sit in a
> open container for a few days before use, and the type that
> just can not be used.

Here are some of my observations on the quality of water that is used
for Nepenthes, in the context of salt/mineral buildup.

First of all, the kinds of minerals I'm talking about are those which
are dissolved in water as ionic salts. I say this, because some Nepenthes
are found in their native habitats growing in soils of high mineral
Soils of high mineral composition are not the same as soils containing
minerals as ionic salts. The former do not affect osmotic balance at
the root/soil interface as much as the latter.

Based on observations of my plants, I can say that the symptoms of
salt-buildup stress in Nepenthes are subtle until the situation gets
bad, and even then the symptoms can be confused with those due to
other causes. At first, the plant growth slows down or stops. Well,
this can be due to a number of causes including seasonal variation
(which is entirely natural). If the condition persists through several
seasons, though, something is wrong. Sometimes the leaf edges
of newer leaves start to get a bit wavy, but again this sort of growth
can be natural for some clones.

The real clue, which shows up when things get pretty bad, is when the
edges of the leaves start to change color from green, to yellow or
red/orange. The yellow or red/orange is not mixed with the green of the
leaf, it is purely yellow or red/orange within a definite boundary. The
leaf tissue in that area is dead. The color change starts at the edges
and then moves inward toward the central leaf vein. To the
inexperienced eye, this color change might be confused with that due
to stronger light conditions. Sunburn can cause this sort of thing, though
that sort of color change is usually superimposed on the green of the leaf.

If the plant has not experienced a sudden increase in light levels, then
cause of color change can be eliminated.

Salt buildup occurs gradually in my growing conditions, over a period
of 9-12 months. That's another reason why it's so insidious. I can repot
a Nepenthes in fresh sphagnum/perlite mix and use tap water and the
plant grows quite well for several months. I feel great because the plant
looks happy. After a year, I begin to wonder why the growth slowed down
and I consider seasonal variation. Then the other symptoms show up....
The rate of salt buildup is related to the water quality, the potting media,
and the watering technique. If the potting media is airy enough (like
media) and if the pots are flushed through during watering then you won't
get much salt buildup even with tap water. If the potting media soaks up
water like sphagnum then you're more apt to get salt buildup since
flushing the pots can't rinse away any salts soaked up by the sphagnum.
If you don't flush the pots through, but only moisten the soil and then let
it dry a bit in between waterings, then salt buildup will occur faster.

Another slow, insidious poisoning unrelated to water quality is the use of
colored styrofoam in the bottom of pots. I repotted several plants this
way and they all grew like gangbusters for months. Then some of them
started to show the leaf color change I just described and I couldn't figure

it out for a long time. I then checked the roots of the affected plants. I

found that each one had finally grown roots into the colored styrofoam.
The repotted plants that were still healthy had NOT yet grown roots down
that far. This was a very sneaky poisoning, because the plants started
growing very well at first and then declined after a few months when the
roots grew into the styrofoam. Luckily I read a posting here which
the phytoxicity of colored styrofoam, otherwise I wouldn't have made the

Nowadays I check the quality of the water I use for my Nepenthes; I employ
a pH/conductivity meter. I also use the Tap Water Purifier from Aquarium
Pharmaceuticals (which is NOT the same as a water softener, as some
people mentioned). If very pure water is used, then you don't have to flush
the pots during watering. You can simply moisten the soil, because
evaporation of
the water won't leave any salts behind.

If I have to repot my plants, I want to do it because they've outgrown their
and NOT because the potting media has accumulated ionic salts.


Perry Malouf

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