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Re: [SHADEGARDENS] Lux in flux

Last year I went outside with one of our second grade classess to the school
forest. Since my husband is an electrical engineer, I had a light meter at
my disposal. I place the kids at certain spots along the path where specific
woodland plants were obvious, ie, geranium. They counted the varieity of
plants in a square meter and took a light meter reading. We then tabulated
the date when we returned. Obviously this would need to be repeated over
time, but the light reading and plant diversity were certainly higher at the
edge than in the woods. It was a good experience for these young ones to
begin to try and correlate these factors. Clearly, the light intensity is
different in Wisconsin than Virginia. We northerners burn to a crisp when we
head south for a winter break. Our plants would respond similarly I assume.
I hadn't given this too much thought, but will now feel free to move my
potted rhodies into more sun and see what happens. I am also looking at my
hostas that I tucked in the deep shade that haven't done as well as I
thought and try them in more light next year. As ha been said here before,
it is a matter of trial and error and a lot of fun.
Heidi
Zone 5b
It's kick-off time


At 12:53 PM 1/25/98 -0800, you wrote:
>Dear Sombreros,
>
>With some of the criticism being directed at how plants do not feel emotion
>most of you may have to admit that the topic was still within one of the
>topics listed as Kosher. We are trying to define what shade is. And unless
>one defines the terms first, how can we plunge into the topic?
>
>The present method of measuring light in units lux (metric) and foot candles
>(the amount of light one candle puts out measured from a l foot surface a
>foot away) is used by theatre lighting people and by movie set designers.
>Most modern hand-held photographic light meters will readily convert from
>f16 or f5.6 to foot candles. For the purposes of light hitting a plant under
>a tree  we would have to create a foot candle unit/time. Plants need a
>certain amount of light over time.
>
>In trying to determine what shade is anywhere there is another factor some
>of us might not know about. This is the Inverse Square Law. The law states
>that at a light intensity s at a distance d if you double the distance from
>your light source you will need 4 TIMES the light not double. What this
>means in lay terms is that plants placed under a tree get a rapid
>deminishing light intensity as you move them closer to the trunk.
>
>I am not smart enough to figure out what would happen to the light under a
>20 foot maple as compared to the light under a 40 foot maple. Would the
>light be the same?
>
>Spanish sherry is Spanish sherry because the grape vines grow in very chalky
>white earth that reflects back the light and heat. The back of Hosta
>hypoleuca leaves are white for an opposite reason to reflect back onto the
>cliffs the light and heat coming down on the mountainside where this hosta
>grows in Japan.
>
>Also not considered in measuring shade is the different types of light
>spectra that hit plants as they go through red leaves, green leaves and
>other types of tree leaves. The light at different latitudes and differing
>pollution levels will also have a fluctuation in quality either toward the
>blue end or the red end if the light is measured in degrees Kelvin by a
>colour meter. Although I know nothing of growing plants under lights I have
>seen different light sources advertised as full-spectrum. What would they
>mean by that?
>
>What is dappled shade? Mottled shade? I think these terms are not accurate
>particularly when you are trying to grow Meconopsis grandis.
>
>Alex
>Vancouver Zone 7/8 but sometimes 6.
>
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