What we are attempting to construct is the perfect conditions for producing
new dahlia plants from
our stock of tubers from the previous season. For this reason I have broken
the growing room into
four separate areas of equal size.
The area for maintaining stock tubers.
The area for potting and striking cuttings.
The area for rooting cuttings.
The area for growing on plants.
Each area for ease of construction is 4 foot square.
The most important factor to be aware of at the start is whether the growing
room is inside a sealed building,
ie. house or whether the growing room is to be constructed in a green house,
this will affect the lighting,
heating and ventilation requirements of the growing room.
In a house, the growing room will need forced vantilation (fans) high light
levels (more lights) but less heating.
In a greenhouse we need fewer fans and less light but may require more heating.
For growth plants requre Light, Heat, Carbon Dioxide and Moisture + Nutrients.
Lighting.
There are a huge number of Light fittings available for the amateur gardener.
From Sodium ballast lamps and
Mercury flourescent fittings to Incandescent light bulbs and ordinary Flourescent
strip lights. The best option
for a small growth room for dahlias is an Ordinary flourescent light of about
36 watts. This light is both
inexpensive and highly suitable for use in a growing room. Wherever possible
always use waterproof light units
in green houses and where humidity is high such as in the growing and propagating
areas.
Sodium lights are relatively expensive use far more energy Typically 200-400
watts and need far more headroom
than a Flourescent strip light. Mercury flourescent lamps are similar to sodium
lamps but produce more light in
the blue end of the spectrum. Warm white flourescent lamps have a similar spectral
range to natural daylight.
My favoured method of lighting a growing area is to use Polycarbonate cased
flouresent lights fitted with warm
white tubes. These are resonably inexpensive (£35 each), energy efficient
at 35 watts apeice and waterproof
so minimizing risk of electrocution if they get wet. where possible check that
the lights are rated to IP55 or
above. Control of the lighting is via a domestic central heating timer wired
to a relay for switching purposes.
It is advisable to use a timer with battery backup to negate the need for reprogramming
the timer should the power
fail. Both timer, relay and lights should be fitted with fuses of a suitable
rating 3-5 Amp is advisable depending upon the loading.
It is recommended that control systems should be fitted away from the damp areas
within the growing room.
Heating.
There are also a number of options for heatind a growing room, electric, gas,
oil or biomass.
Electric heating uses either a fan assisted heater or heating tubes for air
heating combined with either
heatwave panels or soil warming cables for bench heating. Both should be thermostatically
controlled
to control the temprature of the air and bench and prevent cooking of the plants.
Gas heating of a growing room can be by a number of different methods. Forced
air gas heating or fan assisted
direct fired boilers rapidly raise the temprature and are economic due to their
automatic ignition negating
the need for a pilot light. Non electric heaters have a mechanical thermostat
and a pilot light, these are cheaper
and less prone to mains electric power failure.