The adequate climate for growth of Phalaenopsis
is high temperature, high range of humidity and low light intensity. The
adequate climate for flowering is low temperature and high light
intensity than that at growth stage. No natural climate fits for the
Phalaenopsis culture in the United States. Therefore, a greenhouse
with environmental control equipments is essential for Phalaenopsis
industry in this country.
The major production area for orchids is California,
Florida and the northeastern region. Each region has special climate
characteristics. The weather conditions for the four regions are as
1. Southern California:
This subtropical zone is dry in summer, with little
rain. Summers are very hot and winter is mild.
2. Northern California:
This temperate region has an oceanic pattern. The
temperature of the coldest month is >
3. Northeastern region:
This temperate region has hot summers and temperature
of the coldest in winter is < 0℃.
The climate is subtropical humid, usually on the east
side of the continents. The summer rainfall is high, with rainfall
throughout the year. There is no drought in summer.
No universal greenhouse design can be applied to all
orchid production regions. The greenhouse design and its devices for the
four regions are as follows:
The possible layout for a Phalaenopsis nursery
includes hot and cold sections. The hot section is used for growing and
the cold section for spiking and flowering. The setting temperatures of
the hot and cold section are affected by the variety. The setting values
of environmental control system are very important for a Phalaenopsis
The typical weather for Riverside, Los Angeles is in
Figures 1 and 2. Light intensity and period are stable in this region.
The light environment is good for Phalaenopsis.
The average and maximal temperature distribution is
sin Figure1. In summer, the average day temperature is about 35℃ and the
average night temperature is 18℃. In winter, the day and night average
temperatures are 20℃ and 5℃. The night temperature is < 20℃ throughout
the year. Inducing and flowering of Phalaenopsis is easy in this
region. However, the high day temperature could affect the flower
quality in summer.
The absolute temperatures are in Figure1. The highest
temperature is > 40℃ from March to October. The evaporative cooling
equipment is the basic equipment for the Phalaenopsis greenhouse.
The absolute low temperature pattern indicates the lowest temperature
was < 0℃. To maintain the flower quality, heating devices need to be
installed in the greenhouse. The heating capacity needs to be increased
20℃ in the greenhouse.
The advantage of this region is the low humidity. The
day temperature is high in the summer. However, the low air humidity
helps the cooling ability of the evaporative cooling technique. The
evaporative efficiency is nearly to 80%; the cooling temperature in the
greenhouse is shown in Figure 2. The air temperature during the day for
greenhouse is < 22℃. Thus, inducing spiking for Phalaenopsis is
Greenhouse structure and equipment
The specifications of Phalaenopsis greenhouse
are as follows,
1. Exhaust fans with the ventilation rate is 1.25-1.5
Vol/min. If the volume of the greenhouse in 7200㎥,
the required ventilation rate is 9000-10800m3/min (CMM). The
ventilation capacity for the exhaust fan is 550 CMM. The required number
of fans is 17-20.
2. Pad thickness
The traditional thickness of pad materials in this
region is 5 cm, but too narrow for cooling. The adequate thickness of
pad is from 10 to 15 cm.
3. Roof covering
Because of sand accumulation, the light transmittance
of the cover materials is low. The roof materials need to be cleaned
4. External shading nets
The external shading net is basic equipment to reduce
the light intensity into the greenhouse.
5. Wall materials
Double-layered plastic is the best for
Phalaenopsis. It can reduce the heat transfer between the inside and
6. Internal circulation fans
This ventilation device is important to keep the air
circulating in the greenhouse.
7. Humidifying devices
Because air humidity is low, a humidifying device is
necessary to increase the humidity level in the greenhouse. However, air
circulation is necessary with the humidifying operation.
A. Weather conditions
The weather conditions of the Salinas, San Francisco
are presented in Figures 3-4. The solar hours (Figure 3) is > 10 hours
all over the entire year. In the rainy season (Oct.-Dec.), the number of
solar hours may be too low. However, average light hours are 13.5 in
other months. The solar energy helps the accumulation of dry materials
The high /low temperature distribution (Figure 4)
indicated the highest temperature is 22℃ in September. The low night
temperature is 10℃ from November to the next May.
The natural air temperature is San Francisco is good
for inducing and flowering of Phalaenopsis.
The absolute high and low temperature is shown in
Figure 4. The lowest absolute temperature is below 0℃ and the highest is
40℃. Control equipment is needed to install with these extreme
Greenhouse structure and equipment
External shading nets: to be prepared to reduce the entering
solar energy in summer. Internal shading nets or energy-saving curtains
2. Double-layered wall: could isolate the heat
transfer capacity between the inside and outside environment.
3. Ventilation rate: from 1.2-1.3 Vol/min.
4. Pad material > 10cm thick.
5. Typical humidifying: misting in the air or spraying on the
ground. Humidification and internal air circulation needs to be
6. Heating systems: recommended the hot-air heater and hot-water
The temperature and relative humidity distribution of
Brewster, NY and Ringoes, NJ, are in Figures 5 and 6.
There are four environmental control stages of
1. April and May: ventilation during the day and
heating at night.
2. May to September 15: cooling during the day and
ventilation at night. Air is exchanged between outside air and internal
3. September 15 to October: ventilation during the day and heating
4. October to the next April: heating during the day
The environmental control of relative humidify has
1. September to the next May: humidifying during the
2. May to September: cooling with pad and fans to
increase the humidity.
The air humidity in summer is > 50%, and the cooling
capacity of the internal air temperature is > 23℃. The inside
temperature is not low enough to enhance spiking. If the spiking
function is necessary in this region, a mechanical cooling room needs to
be installed inside the greenhouse with cooling ability controlled by
A. Greenhouse structure and equipments
Wind load and snow accumulation weight are the main
factors for the roof strength in this area. Other required equipments is
External shading net
The local wind pressured is strong, so the net
structure needs to be enhanced.
2. Positive pressure fan
installed at both sides to exit the accumulated heat between the roof
and internal shading nets.
3. Internal shading nets or energy saving curtains.
4. Artificial light: minimum light supply is 6,000 lux.
5. Internal circulating fans to provide air movement in the
6. Pad thickness: 10cm or 15cm.
7. Exhaust fan: ventilation rate 1.25 Vol /min.
Two stage curtains at outsider pad structures: In winter, intermittent
air movement is necessary to exchange the inside and outside air.
However, cool air could be cooling stress for plants. A special device
is used to change the cool air direction to react with plants directly.
9. Misting equipment: to humidify the inside air.
heater and hot-air heaters.
Light curtains: at both sides of the greenhouse. The curtains are open
in winter and closed in summer.
The typical weather of Homestead, FL, is in Figures 7
and 8. The average maximum day temperature in summer is > 32℃ and the
average maximum night temperature nearly 25℃. However, the record for
the minimum temperature in winter is < 1℃.
The relative humidity of the air (Figure 8) indicates
that humidity is nearly saturated at night and > 60% during the day. The
higher humidity limits the evaporative efficiency of the pad and fan
The cooling temperature in the greenhouse by the pad
and fan system is > 25℃. It is difficult to induce spiking of
Phalaenopsis. Only in winter can the inside temperature be cooled to
< 25℃. This region is good for growth and inadequate for spiking.
The design of the cooling room for spiking is similar
as in Southern Taiwan and so could be applied in Florida.
Greenhouse structure and equipments
The subtropical greenhouse used in Taiwan could be
applied in this region. The basic requirements of such greenhouses are
Resist the high wind speed and heavy rain.
high ventilation rate.
Shading with external and internal nets.
4. Pest control: more difficult than in other
The required equipments included the following:
Exhaust fan with 1.5-1.8 Vol/min ventilation rate.
2. Hot-air heater to increase the inside air
temperature in time.
3. Mechanical refrigeration for inducting of spikes.
4. Internal and external nets.
The details of these novel technologies are as
Algae prevention technology
The exterior of pad surfaces is covered by shading
nets to reduce light intensity. Before the pumps stop, all the water in
the pad is sucked out to reduce the risk of algae development.
Internal circulation fan
The industrial ventilation fan is adopted to
circulate the internal air without inspiring outside air. With special
criteria of the number and installation angle of these fans, the
temperature and relative humidity of inside air could be uniform to
reduce the risk of disease development.
Internal energy-saving curtains
Moveable systems include plastic curtains, insulating
curtains, a driven mechanism and control devices. Curtains could help
decrease the required internal space for heating or cooling. The
required energy cost could be reduced.
Uniform distribution of hot-air heater or hot water heater
The hot air exited from heaters is distributed by the
perforated-tube air circulation system. To ensure the uniform
distribution of hot air, the size and distance of holes in the
perforated-tube was studied by the fluid theory. A software program was
developed to calculate the required open area and to determine the
position of holes. The air distribution with the hot water heater is
assisted by internal fans to ensure uniform temperature distribution.
Silver shading nets
The silver shading nets are used to replace the black
shading nets. The quality of solar irradiance could be modified by this
The installment of the insect screen is to keep out
the insects entering the greenhouse. However, the air-resistant
characteristics could reduce the ventilation capacity. A special design
for the screen installment can avoid air circulation problems.
Cooling house for flower induction.
The cooling ability of the pad and fan system was
limited by the wet bulb temperature of the outside air. Because of
higher humidity environment, the internal temperature is 7-8℃
lower than the outside air temperature. The air temperature of the
greenhouse is usually 27-28℃
in summer. The required flower-inducing temperature is lower than this
range. To ensure that the inside temperature meets the requirement for
spike induction temperature, a special cooling house is designed and
installed in the greenhouse.
Figure 1. The typical weather information in Riverside, Los Angeles
Figure 2. The cooling ability of greenhouse in Riverside, Los Angeles
Figure 3. The sun hour conditions of the Salinas,
Figure 4. The temperature distribution of the
Salinas, San Francisco
Figure 5. The temperature distribution of the
Brewster, NY and Ringoes, NJ.
Figure 6. The relative humidity distribution of the Brewster, NY and
Figure 7. The temperature distribution of Homestead, FL
Figure 8. The relative humidity distribution of Homestead, FL