Phalaenopsis Journal Third Quarter 21(1), 2011 | Page 19

Two simple methods of judging light intensity are described
in the literature. First, hold your hand above your plants. A
distinct outline will indicate the need for shading. Second, if a
leaf feels warm to the touch, then more shade is required. The
alternate is to use a hand-held light meter or the light meter in
a camera. Because cameras are designed to read reflectance, it
is mandatory that the proper reflectance be viewed. Correct
measuring requires filling the entire field of view with a gray
card having 18% reflectance. The camera reading is converted
to foot candles (fc) using the formula found in U.S. Gov. pub-
lication No.125 as follows: foot candles = (f-stop) 2 x 20 ÷ ISO
speed x shutter speed.
Windowsill growers generally need all
the light available from the sun. The lit-
erature indicates that a bright window
provides about 1000 FC. When the sun
is bright and the window receives full
light, it is suggested that sheer curtains
be placed in front of the plants. Before
adding curtains, make certain your
plants will not tolerate more light. If
you increase your light you may need
to increase watering and the rate of air
circulation.
in a greenhouse. Under-light growers can control their light
by changing the number and type of lamps, light distances,
day length, and by building an enclosure.
Both light intensity and humidity are improved by enclosing
your growing area. Basements are ideal with the room located
near a floor drain to conveniently dispose of excess water. In
planning don’t forget the heat generated by any lighting sys-
tem. Your plant room should include an outside vent for the
heated air. The amount of air that must be vented is small. My
large plant room is vented through a small diameter vent. The
room is cooled by drawing replacement air through a small
wet-pad cooling system, similar to the one used to cool my
greenhouses.
Windowsill growers frequently move
orchids outside after the last frost.
When plants are moved outside expo-
sure should be increased slowly over
a period of about three weeks. Some
growers construct a lath house using
slats running north and south which
causes the shadow to move across the
plants.
Outside growers need to increase wa- Basement wall painted to reflect light.
tering because the high light and air movement will dry your
plants quickly. It’s possible but difficult to overwater when
growing outside. Orchids are normally left out until the first
frost is forecast.
If you intend to grow under lights, de-
cide how much light you are willing to
provide. The tendency is to skimp on
fixtures. For example if your choose
T12 lights (1 ½ inch diameter): con-
sider a minimum of 2 light units with
4 tubes each for a total of 8 tubes sus-
pended 4 inches (10cm) above the
foliage. I use Philips Cool White, 48-
inch, 40 watt bulbs with a color temp
of 4100K, and light output of 3200 lu-
mens. I have also mixed cool and warm
bulbs, 4100K and 6500 K. Phals are
placed with the leaves about 6 inches
below the lights for 200-250 fc of light
for 14 hours.
In summary provide your plants with
all the light they can use, which is con-
siderably more than generally recom-
mended. I think you will be pleased
with the results.
Thinking of building a greenhouse? As you calculate costs
don’t forget to include accessory equipment. Include in the
costs a standby generator, generator fuel, a transfer switch, a
backup heating system and a method of shading.
Before committing yourself to moving plants outside or
building a greenhouse consider becoming a light grower. You Fred J. Bergman
may spend less for electricity than heating a greenhouse. With 9401 East 103rd Street • Kansas City, MO 64134-2206 USA
sufficient light fixtures you can grow as well as or better than Fred Bergman passed away, Sunday August 28, 2011.
Phalaenopsis - Vol. 21(1), Third Quarter 2011
19