Help, something is blistering my orchid cactus leaves. Picture is
posted on alt.binaries.pictures.gardens. I've got two or three varieties of
something Wife calls "orchid cactus" growing in the greenhouse. One (the
most beautiful when it decides to bloom) has this blight that I can't seem
to slow down. I don't want it to spread into the others until I learn
something about control.
Each little spot seems to start with a little watery blister, and then
dry up into a much harder brown blister. I thought at first it was some kind
of a bug inside the early stage blister. I popped one or two open and using
a 10x glass looked for something squirming or with legs...... nothing I
Is this ailment something anyone knows about? And also I'm sure that
there is a better name for the plant than "orchid cactus"..... maybe some
help there too!
Thanks in advance!
Lynn (really rank amateur greenhouser)
Your plants are epiphyllums, commonly known as orchid cacti. Your condition
is rather common. While it could be caused by sucking insects, the spots are
more commonly caused by either water left on the plants in full sun causing
sunburn (water drops act as lenses magnifying the light to burn small round
patches), or by overwatering at a time of the year when the temps are lower
and the plant cannot use or get rid of excess water. Epiphyllums are rarely
hit by fungi, at least on the "leaves" (stems). And the most common insect
problem is mealybug which is easily seen. Give your plants a winter rest by
reducing water and fertilizer especially if they're not in full sun or
receiving full natural light, depending on your location. Good growing.
Thanks for all that good information. The overwatering and/or too much
fertilizer is a condition that is quite possible. We used a LOT of water to
keep the pot heavy enough to keep from falling off the shelf. Dumb, dumb,
dumb gardening, I know...... perhaps lazy is also a factor.
On Thu, 29 Dec 2005 08:09:48 GMT
] Water drops cannot act as a magnifying glass.
Travis, you seem fond of unequivocal statements... I'm not
sure if you're trolling or what, but a water drop certainly can
act as a magnifying glass. Imagine the geometry of a drop,
it's easy to see how it acts as a lens.
Don't take my word for it, google "water drop magnify physics"
and follow any link, the first will do.
Just wanted to clear that up for anyone without a physics
You can reply to email@example.com
The water droplet myth explained so even those WITH a physics degree can
Still showing up in some popular garden literature is the notion that
"day-watering" or water droplets can burn plants. The notion says that
sunlight is "magnified by the water drop on the leaf to cause a leaf burn.
Anyone who ever burned ants, paper or anything else using a magnifying glass
and the sun knows that the magnifying glass did not burn the ant if it were
placed directly on the ant. Rather, it had to be held a distance (focal
distance) from the ant to concentrate the sun's rays enough to burn the ant,
If this notion were true, all gardeners would cover all their plants prior
to every rainstorm.
Farmers would not be able to prevent widespread "leafburn" after rain clouds
gave way to sunshine. The root of this notion may have come from the
effects of applying poor-quality water high in dissolved salts. As water
drops evaporated from leaves,the salts left behind could cause a leaf burn.
This will often happen if the water is from a tap hooked to a water softener
system........and probably a lot of other reasons there would be high salt
concentrations in the water that I'm sure if those who want to Google the
hell out of the day, will be able to find.
The sun just came here Travis, wait 5 minutes and you'll probably get some
Val in Ballard (just south of Travis) Washington
Sorry, Travis, but I partially disagree with you. While your general
statement is true, there are specifics that can certainly vary.
First, you do not have to be at the focal point for damage to occur,
particularly over time. Heating of the tissue under the droplet can cause
necrosis. Secondly, the water droplet may be almost spherical on hydrophobic
waxy surfaces thus shortening the focal length. And thirdly, the thickness
of the waxy layer can add more distance to the focal distance and in effect
raise the focal point closer to the surface. While it's agreed that this is
probably not the cause of this epiphyllum's problems, it's certainly not out
of the realm of possibility, which you seem so certain of, for other cases.
Thanks to everyone for all the help. This last one about edema, and the
pictures on the "link" seem to fit quite well. I've pretty near stopped
watering the one plant with the problem, and it has grown some new leaves
(is that what they are called?) without the blistering. I'll try to be more
aware in watering when it begins to heat up again here in NW Washington.
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