Very good answer Al, I love reading your 'stuff' (for lack of a better
work), you should retire & write books.
But Gannet has a hard covered roof so wouldn't he have a period of time with
no rays?
Now I have another question, could you use mirrors to deflect the sunlight?
Cheers Wendy
"Al" wrote in message
...
My horticulture teacher told me that 'full sun' was defined as 5 hours a
day
or more of direct sunlight. Maybe this was just an 'off the cuff'
definition but it helps one to keep in mind that the light requirement to
flower a plant is more than just intensity (foot candles) it is also
duration. A single foot candle measurement gives you only part of the
story.

Direct sunlight for 5 hours in Florida may be essential to some very high
light level plants, like Vanda if you want them to bloom. Direct sunlight
on Vandas may not be enough to get them to bloom if this sun light falls
on
them at the north pole for 24 hours a day. :-)

Direct sunlight on a Phal in my growing environment only works in the
winter
when intensity is off by 30% of the summer high and then only in the early
or late parts of the day when the angle is very great and then only for a
matter of minutes rather than hours. Air temperature and relative
humidity
also plays a role in how much direct light can fall on their leaves
without
causing them to burn, I think.

Light, direct or indirect, must be of a certain intensity and wave length
to
excite the chlorophyll molecules to do their job. And this intensity and
correct wave length has to occur for a certain amount of uninterrupted
time
in a 24 hour cycle. If you are using the sun light, the wave length is
not
going to be a problem. Low intensity can be somewhat offset by increased
duration. This is why people using artificial lights which are typically
lower in intensity than natural lights use increased duration. Decreased
duration can allow increased intensity. Think of sunlight filtered
through
gently moving leaves from the tree branches above an orchid plant. Here
very direct light falls on the orchid but only briefly and never for so
long
as to cause the leaves to overheat and burn before the shadow of the
filtering leaves causes the intensity to decrease.

"Indirect vs. direct" may be just your friend's way of looking at the
gestalt in his growing environment to help him make sense of his
observations and to communicate them to you.

Eventually, as you progress in this hobby, you will learn to let the
plants
themselves tell you what light levels they want. And they are all
individuals in their needs. You are already well on your way to this
realization because you are watching the leaf color. Also watch for
relative tissue thickness, relative strength of new growths, stem length,
flower color intensity, etc...

There are a lot of factors involved in blooming too, obviously. Not just
light intensity. If your plants are mature and all other aspects of your
culture are correct for them, you should see blooming over the course of a
year or so sufficient for you to determine if the light levels and
duration
are good. A few months of observation is probably not enough time for you
to know yet if you are on the right track.

The assumption here is also that if the plant flowers it must be grown
correctly, with the 'right' light levels, proper temperature, etc... :-)
In addition to flowering on a regular schedule, also look for proper light
levels to help the whole plant to increase itself. A plant which gets
good
enough light to bloom every year but still limps along without making side
shoots or multiple leads may not be really getting the light levels it
wants. Of course this is all relative to the vigor of the individual
plant
in question.

Wendy" wrote in message
news:Uv21b.28917$kP.21191@fed1read03...
Hi Gannet, If you walk into a forest & a tree falls,........will you see
the
light? *G*
I am not that savvy when it comes to foot candles but I would say the
guy
is
correct!
In order to grow the higher light requiring plants you would need an
open
roof with shade cloth.
I was told to hold your hand about 18" above the plant & you should see
a
slight shadow.
I would think you need direct shaded sun 'rays' the entire day.
Having said all this, I have Vandas (high lighters) that face south
east,
that bloom. They are
shaded by the house from about 3pm onwards?
Cheers Wendy....Just my tickies worth.
wrote in message
...
YANQ - Yet Another Newbie Question

Is direct light essential?

It's a little hard for me to find growing info appropriate to my
situation (South-facing open, hard-roofed, second-floor balcony right
on Tampa Bay in St. Petersburg, Florida), so I thought I'd go talk to
one of the local purveyors. This particular place (Art Stone Company,
for any locals) has been there for years and is clearly the result of
hobby-gone-wild. Point is just that I assume the guy is fairly
knowledgeable.

Light levels in the shade are 500-2000 footcandles, depending on how
close you are to the front. Light levels out by the railing are, of
course, Florida-level, at 12-16000 footcandles. I also took
measurements in his greenhouse and the numbers were similar. His
brightest areas were a bit brighter than my brightest, and his darkest
were darker than mine, but all-in-all, quite comparable.

And yet, when I described my growing situation, which is this
hard-roof balcony, he seemed fairly pessimistic. I didn't have the
numbers in footcandles at that point, but I said the numbers were
about the same as home. He said that the indirect light didn't count
as much, and that my light levels were quite low. He advised Phals,
and said that while other orchids would grow, they would be unlikely
to bloom.

I've had a few orchids growing here for some months now and the leaves
have not gone dark green. No blooming, but that's as likely due to
other aspects of newbie husbandry.

So, what's the scoop? Is the guy right? I'll tell ya, for a
roofed-over porch, it's pretty bright! I actually had to move one
Phal back towards the back wall, as the leaves lightened up a lot.

Is direct light essential? As long as I get the light levels required
on the meter, is that "good enough" or not?

TIA

Gannet
St. Petersburg, Florida