Your plants want bright indirect light. They sunburn,
just like we do. I would keep them in the shade, but with some sort of semireflective
surface nearby that reflects sunlight to them without the direct burning rays
touching their fair skin. I do this with many of my hardier plants.
Invertebrate Ecologist/ Taxonomist
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From: firstname.lastname@example.org [mailto:email@example.com] On
Behalf Of Theodore Held
Sent: Tuesday, June 16, 2009 11:42 AM
Subject: [Aroid-l] Chlorophyll and Sunlight
I am always tempted to move certain of my plants outdoors
summer. My wife refers to this as having my plants go to
Here in the North (Michigan) many plants weaken if they
live for years
on a window ledge. My typical thinking is that a short
in sunlight in a natural setting will re-invigorate a
theory is sort of correct. The plants do derive a dose of
they overcome the shock of the change.
The problem comes with the transition from one to another
especially going from indoors to out. I see this
described as “sun scald”, which entails a kind of
coupled with desiccation. What this means in practice is
a loss in
appearance, often including the functional killing of the
foliage. While this is usually overcome by the growth of
leaves, there is no doubt that sun scald is a setback.
Some experimentation will show that sun scald is more
overexposure to intense sun. It will also happen if the
plants are set
out in shady areas, even in what is known as “deep”
shade. One can
also mitigate water loss as a cause by sheltering and
frequent mist. Scalding still occurs.
What is it about the outdoors that causes sun scald?
Here is an example of one of the most severe cases. For
the past few
years I have rejuvenated my Pistia (aroids) with a summer
every year. By September, helped by additions of
fertilizer, my Pistia
are big and bountiful, harboring an abundance of small
indicate horticultural contentment. Over the winter the
individuals regress anew and are ready for summer camp once
When the plants are moved outside, they turn white within
a day or two
of the new harshness. This is sun scald with a vengeance.
To be sure,
tiny kernels of life remain at the plants’ centers and
starts at once. But the bulk of the leaves have not only
they have been bleached white. Within a week the former
have been converted to a minor remnant of white mush. The
color indicates to me that the chlorophyll has been
destroyed. It is
always surprising that the plants are not killed and that
bigger and more vigorous than ever within a month.
I have heard the theory that summer leaves grown outdoors
tougher “cuticle”, referring to a transparent layer that
inner goodies from harshness. I have also heard the
theory that the
leaves arising in outdoor conditions have fewer stomata
on the leaf
undersides. It seems there are hardened leaves produced
“hothouse” leaves produced under protected conditions, presumably
allowing readier access to what little light there is
with what is received from nature directly.
But is also seems as though the hardened leaves also have
a degree of
screening power against ultraviolet (UV) rays. I assume
here that UV
is what attacks the chlorophyll.
Do we have any authorities on these maters tuning into
the list that
could comment and clear up these matters for me? I hold
out hope that
there are one or two.
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