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 This is a continuously updated archive of the Aroid-L mailing list in a forum format - not an actual Forum. If you want to post, you will still need to register for the Aroid-L mailing list and send your postings by e-mail for moderation in the normal way.

  leaf burn causes?
From: Ferenc Lengyel <feri.lengyel at gmail.com> on 2014.11.09 at 19:40:17(23155)
Dear Aroiders,

I know that this question is not aroid specific but I know
no other forums where I could ask it (and it incudes aroids).

Does anybody know what physiological difference might cause leaf
tip in some aroids, but not in others? I have some Philodendrons, a Dieffenbachia
cultivar, two different Syngoniums, a
Spathiphyllum cultivar, Epipremnum aureum, an Aglaonema and Monstera deliciosa (I had another Monstera with small leaves, but it has died). Of these genera, Monstera, Spathiphyllum and Epipremnum
aureum shows leaf tip burn (the tip of the leaves becomes necrotic)
followed by necrosis of the whole leaf. Monstera
deliciosa is a hard plant to kill, but here in my appartment it can not develop
normally, the leaves become necrotic. It applies to Epipremnum aureum, another easy houseplant too. The same might be
the situation with Spathiphyllum, but
I bought it recently and I mainly watered it with deionized water. Lately I
gave it tap water and it started to exhibit leaf tip burn too. I had another Monstera which has perished after
necrosis of all of its leaves. On the other hand my Philodendrons, Dieffenbachia,
Aglaonema and Syngoniums are not affected at all.

In my aquarium I had Anubias
plants which suffered from nercosis of their leaves too. They perished (I used
1:1 mixture of tap water and deionized water).

My non-aroid plants suffering from leaf tip burn include Dracaenea fragrans (necrosis is limited
to leaf tips) and Chlorophytums. I
have Chlorophytum comosum (again a
plant nearly impossible to kill) and a Chlorophytum
orchidastrum cultivar (’fireflash’). Both suffer of severe necrosis and loose
all of their leaves and die when watered with tap water. When I water Chlorophytum with deionized water (once
a month or so with citric acid dissolved in it to lower pH) my Chlorophytums do much better. It is
interesting as I read that Chlorophytum
comosum is sensitive to fluoride and raising the pH of the water (that is
the opposite what I do) helps by decreasing solubility of fluoride ions.

My non-aroids not affected include a Vriesea cultivar (I know that bromeliads should not be watered with
tap water but recently I started to do so with no problems) and a Schefflera.

Th pH of our tap water is around 8.0 and that of deionized
water is around 5.5. Light levels are low but Monstera deliciosa must not die where Philodenrdons live and grow.

The plants do not suffer from a „bad gardener” as at my
workplace my Mosteras florished. There lives the motherplant of my M.
deliciosa and it is huge, without any leafburns and the small leafed
species (which I lost here at home) grew well without any blackening of the
leaves too. Sunburn, under- or overwatering, too heavy soil mix should be excluded (maybe it is not the right word... I mean, do not consider them).

Maybe it is not the water, but I can not think of anything
else. Monstera deliciosa and Chlorophytum comosum are so easy plants
to grow and make thrive that it is really strange that I can not even keep them
alive here at home.

Do you have any idea?

Ferenc

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From: Theodore Held <oppenhauser2001 at gmail.com> on 2014.11.11 at 17:41:30(23162)
Ferenc,

I am probably not the best person to answer your inquiry. But seeing no responses as yet, maybe my words will induce the more knowledgeable members to chime in.

I stopped my Spathes from experiencing leaf tip burn by taking the advice of the late Steve Lucas who indicated to me that he grew his in an almost swamp-like aquatic planting, with the roots continuously wet (that is, soaking in a puddle of standing water). Once I tried his technique all my new leaves stopped having tip burn and they continue to be fully green to this day (five years now). My water is pretty good, being relatively low in conductivity and moderately alkaline pH (in accord with desired municipal practice). I do not fuss with mixtures with DI water or trying to modify the pH.

One factor you might consider would be the relative humidity of the surrounding air. Assuming that wet feet would not be desired for many species, having a low relative humidity might put stress on leaf tips on those varieties with more normal water likes. This might also account for your seeming success at work with problems at home. Just a suggestion.

I also grow Anubias, but mainly in a submerged state. I never have any sign of abnormal necrosis with these. When I have grown them with leaves emergent I have also never had and tip burn or abnormal necrosis. This one is a mystery to me. I also would not exclude the possibility of disease.

Other factors that might be in play are those involved with horticulture taken as a whole: light level, air movement, temperature, environmental variables such as day-night fluctuations. My advice would be to take notes on anything you might think about and compare the environment where you are successful to where you are not.

Ted Held

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From: "derek burch" <dburch23 at bellsouth.net> on 2014.11.26 at 00:52:00(23170)
Definitely keep thinking of Fluoride in
your city water. It has ruined many crops of the leafy aroids for nurserymen all
over the place. And the person who mentioned the raising pH to help the
situation is definitely right. I used to find in nurseries that the plants that
remained in one size pot would show symptoms as the media gradually acidified.

Derek

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From: Ferenc Lengyel <feri.lengyel at gmail.com> on 2014.11.27 at 09:27:52(23171)
Dear Derek,

I have read about the fluoride issue, but our tap water has a pH somewhere between 8.0 and 9.0 and I have not tried to raise the pH any further. What is more, using distilled water and sometimes acidifying it seems to eliminate the problem. So I am really confused.

Ferenc

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From: "Weaver, Bill (NorCal DCIS Team Lead)" <bill.weaver at hp.com> on 2014.11.28 at 03:40:53(23172)
Sure sounds like a buildup of salts. What is the Total Dissolved Solids (TDS) of your water sources? What is the TDS of the water in the immersed pots? You can have really good water and still end up with a fatal salt buildup.

------ Original message------

From: Ferenc Lengyel

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From: Theodore Held <oppenhauser2001 at gmail.com> on 2014.11.29 at 20:50:25(23174)
Just for information purposes, I exist on city water here and it is fluoridated. Most municipal waters in the United States have small amounts of soluble fluoride. Large amounts can, indeed, be toxic. But the rules for fluoridation keep the level quite low and it should be safe (see my comment on salt buildup, later). As I mentioned previously, my experience here is that the leaf tip burn goes away with sufficient moisture and my practice to keep them moist uses only plain tap water. Most municipal waters in the U. S. also contain a small amount of chlorine as a disinfectant. The chlorine dissipates quickly upon sitting (overnight). I also have chlorine in my trap water.

Recall also that all (almost all?) municipal water sources are also lightly alkaline, meaning a pH in the range of 8 or 9. The reason for that is to minimize water pipe corrosion. This also applies to my water supply, which originates from the Great Lakes.

One problem that people sometimes have is keeping their plantings for extended periods without refreshing the soil (whatever the composition). If tap water (or well water) is added from time to time (except for deionized or distilled water, from which no salts will originate) salts gradually build and can lead to "burn" phenomena. The kind and extent of dissolved salts in your water can be seen by evaporating some of it in a clean glass vessel. Look for the milky white residuals. These are salts. Water used to keep plants wet will transpire through the leaves and evaporate from the soil, but any salts will be left behind. To some extent excess salts can be purged with leaching and subsequent disposal of the leachate. People often ask me about the "calculus" of whitish salt that appears on pot rims over time. This is mostly calcium sulfate (gypsum). It is diagnostic of an accumulation of salts in the potting medium, although the calc is not soluble in new added water. Fluoride used to treat tap water is a typical salt and is not volatile. It also gets converted in horticulture to a very insoluble form (as calcium fluoride), meaning that it will not be flushed with a leaching. That means fluoride will accumulate as a planting ages without periodic refreshing of the planting mix. (My guess is that since calcium fluoride is so insoluble it must be essentially inert once created.)

Finally, it should go without saying that once tip burn occurs it will not go away. Brown tips are dead tissue. Success with any remedy will need to be noted on new leaves as they appear. If you are successful the new leaves will stay green while the affected leaves will stay with their brown tips. If you have a big display of Spaths, it might take a couple of years or more of better growing conditions to finally have a planting without brown tips, as old leaves die off and are replaced by nice green ones.

Ted Held

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From: Steve Marak <samarak at gizmoworks.com> on 2014.11.30 at 17:33:28(23176)
I'll add a couple of comments to Ted's excellent note on water
quality.

Even with relatively good water - low in dissolved salts - there is
a lot of difference in how salts will build up in medium on a
greenhouse bench, where leaching water can run straight through the
pot and carry salts with it, compared with the same pot in a tray or
saucer or other place where water is held at the bottom of the pot
(and the medium inside) until it evaporates.

I keep a very few plants on a windowsill at my office, so they're in
a tray. Even though I use only deionized water, which has
essentially no dissolved salts, salts that dissolve from the medium
itself, plus salts in the fertilizer I use periodically, have
nowhere to go and so build up in the tray. With the next watering
those deposits will redissolve to whatever extent their solubility
allows and can produce surprisingly high TDS values relatively
quickly, and if the pot sits flush in the tray that solution
permeates the bottom of the medium. Since I'm lazy about repotting,
I wash out the tray every few weeks and periodically flush the pots
in a sink.

Also, some media are widely considered to "hold" salts from water
and fertilizer better than others, and so need replacing more often.
I haven't seen any rigorous measurement, so take this with a grain
of (undissolved) salt, but I know orchid growers who believe that
sphagnum moss must be replaced as often as every six months if you
are feeding regularly.

Some water supplies are switching from chlorine to chloramine as a
disinfectant, because it's more stable and thus is effective longer.
But that also means you can't get rid of it just by letting the
water stand for a day or two - it requires special treatment. As
usual - think fluoride - there is a lot of debate over the safety
and desirability of chloramine. I haven't seen any reports of plant
toxicity, but I know there are aquarium enthusiasts who have had big
losses when their water supply switched to chloramine. (Chlorine is
toxic to fish too, just easier to remove.)

Note also that very pure water, which has a theoretical pH of 7.0
dead on, if left exposed to the air will quickly become somewhat
acidic as gaseous acid anhydrides from the air, mostly carbon
dioxide, dissolve into it. What the value will be when equilibrium
is reached depends on what's in your air, but for typical levels of
carbon dioxide the theoretical pH is 5.6-5.7 - and indeed when I
measure rain water here (northwest Arkansas), it's pretty close to
that. That's 100 to 1000 times as acidic as our tap water, which
like Ted's is adjusted up into the 8-9 range. Surprisingly, to me
anyway, most plants don't seem to mind the higher pH of tap water,
but we switched to reverse osmosis water in the greenhouse, and our
unscientific observation is that the plants grow better.

Steve

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