There are two
primary types of lighting used
to grow plants. High Intensity
Discharge (HID) is by far the
most common, and includes Metal
Halide (MH), which is used
primarily for the vegetative
stage of growth, and High
Pressure Sodium (HPS), which is
used during the flowering or
fruiting stage. You can find
more information on HID lighting
further down in this FAQ section.
Another popular type of plant
lighting is Fluorescent lighting.
Fluorescent lighting is used
primarily for starting seedlings
and cuttings, but T-5
fluorescent bulbs are strong
enough to grow short plants from
start to finish. It is important
to note that not all fluorescent
lighting is the same and only
certain types should be used for
growing plants. Most (if not all)
standard fluorescent tubes are
fine for illuminating a garage
or office, but usually lack the
spectrum and intensity needed to
sustain plant growth. It should
also be noted that if you are
growing houseplants that require
very little light to sustain
growth, you can probably get
away with some of the inferior
types of fluorescent lights. But,
if you are growing plants that
need plenty of natural sunlight
in order to thrive (such as
vegetables and flowers), you
will be extremely unhappy with
the results you get from these
bulbs.
There are three types of
fluorescent bulbs that are
considered suitable for plant
growth: Standard tubes with
enhanced spectrum (such as the
Verilux), Compact fluorescents
and T-5 fluorescents.
Verilux
Verilux bulbs look similar to
the bulbs you typically find in
shop lights and offices. The
main difference is that, unlike
standard tubes which lose their
intensity and spectrum in as
little as 6 weeks, Verilux tubes
retain their properties much,
much longer. They also have a
spectrum that is extremely close
to natural sunlight. They can be
used in any standard shop light
fixture. They should only be
used for growing houseplants,
orchids, or for starting
seedlings or cuttings.
Compact Fluorescents
These bulbs are available in a
variety of wattages ranging from
95W up to 200W. They produce a
higher lumen output than regular
fluorescents, and are available
in 6500K (daylight) for
vegetative growth and 3000K (red)
to enhance flowering. Unlike
regular fluorescents, compact
fluorescents do not require a
fixture, since the ballast is
built in to the base of the bulb.
They require a socket (the same
type of socket you would use for
an HID bulb) and a power cord,
and can be used with or without
a reflector. Using a reflector,
however, will direct more of the
light down onto the plants.
Another common use for compact
fluorescents is to hang them
vertically, usually without a
reflector, in between large
plants to provide supplemental
side lighting. Compact
Fluorescents can be used for
growing houseplants, orchids, or
for starting seedlings or
cuttings. For plants that do not
require full sunlight, or for
varieties that tend not to
stretch under weaker light,
these bulbs can be used for the
entire vegetative stage, and in
some cases flowering as well.
T-5 Systems
T-5's are the best
fluorescent light bulbs
available. They are similar to
standard fluorescent tubes, only
much smaller in diameter. They
put out far more light then
standard fluorescents, and have
a much better spectrum as well.
T-5's must be used in a T-5
fixture; they will not work with
standard fixtures. They are
available in different sizes and
configurations, ranging from 2'
two bulb fixtures up to 4' eight
bulb fixtures. The eight bulb
fixture is approximately
equivalent to a 600W HPS
lighting system. T-5 bulbs are
available in 6500K (daylight)
for vegetative growth and 3000K
(red) to enhance flowering. T-5
systems are excellent for
starting seedlings and cuttings,
and in many cases take plants
from start to finish, provided
you keep the plants on the short
side.
The rest
of this lighting FAQ pertains
mainly to HID lighting systems.
What size (wattage) lighting
system do I need?
There are two things to
consider when deciding what size
lighting system to use: the
actual area in which the plants
will be taking up, and how tall
you want your plants to grow.
150-175 watt lights are
primarily used for seedlings or
cuttings, though they can be
used for growing plants to
maturity if the plants are kept
short. 250 watt systems are good
for areas up to 2.5' square at
the most, as long as the plants
don't get taller than about 2'.
400 watt systems cover a primary
area of about 3' x 3', or up to
4' x 4' max. 600 watt systems
cover a primary area of about 4'
x 4', or up to 5' x 5' max. 1000
watt systems cover from 4' x 6'
up to 5' x 7'. The taller you
plan to grow your plants, the
higher the wattage needed. This
is because the light intensity
diminishes by 50% for every foot
you move away from the bulb. So,
if your plants reach 4' tall,
then the leaves at the bottom of
the plant are receiving only
around 12% of the light that the
top of the plant is getting!
Click here for a
hydroponic lighting chart
showing the dimensions that each
light system will cover
REFLECTORS:
The reflector is undoubtedly the
single most important factor to
consider when choosing a
lighting system. The reflector
dictates whether the light is
concentrated on the plants, or
splashed up against the walls.
While some bulbs are a little
brighter than others, a quality
reflector can reflect up to 50%
more light straight down onto
the plants than a lower quality
reflector. Here's a common
mistake that first-time growers
make. They see a reflector that
is advertised as covering up to
an 8' x 8' area (with a 1000W
bulb installed). Then they see
another reflector advertised as
covering only a 4' x 6' area,
and for more money, too! Which
would you choose? Well, consider
this: Let's say that a 1000W HPS
bulb puts out 140,000 lumens (lumens
is a measure of light intensity).
Now, let's say that you have a
jar containing 140,000 marbles,
each marble representing one
lumen. You pour this jar into an
area that measures 8' x 8'. You
get a pretty thin layer of
marbles. Now, pour this same jar
into a 4' x 6' area, and you
have a much thicker layer of
marbles, right? Is it starting
to make sense? Stay away from
the reflectors that throw the
light all over the place, unless
you are growing houseplants! The
smaller the area covered, the
brighter it will be, and the
better your plants will grow and
yield. Horizontal hoods are the
best choice for plants that
require a lot of light, such as
most vegetables & flowers.
Horizontal hoods direct the
light straight down on the
plants, throwing more intense
light over a smaller area. This
is by far the most popular
choice among growers. Air-cooled
hoods have flanges that allow
you to hook an exhaust fan to
the hood to suck out the hot air
generated by the bulb, thus
reducing the amount of heat in
the grow room.
BULBS:
How often do I need to replace
my bulbs?
HydroGrown Hydroponics
recommends that HPS bulbs should
be replaced at least every 12
months (8 months or less is
ideal). MH bulbs should be
replaced every 9 months (6
months or less is ideal) for
maximum efficiency. The use of a
light meter would be the best
and most accurate way in which
to measure your bulbs output as
well as to help with bulb
replacement timing.
What is the difference between a
MH and Super Bulb and how do I
know which one I need to buy?
A Metal Halide Super Bulb has a
higher lumen (light) output, and
is almost always position
oriented. These bulbs have a pin
sticking out of the side of the
mogul (base) where the bulb
screws into the socket. These
bulbs require a position
oriented socked that is designed
to catch the pin so that the
bulb is rotated into the correct
position, otherwise the bulb
will not perform as expected. In
addition, these Super MH bulbs
must be burned in a horizontal
position only. All other bulbs (non-position
oriented), including the MH
Regular bulb, can be burned in
either a horizontal or vertical
position (i.e. they are
universal) unless otherwise
noted in the individual bulb
description.
GENERAL:
What is a recommend lighting
schedule for Vegetation and
Flowering?
For Clones/Seedlings and
Vegetative Growth
HydroGrown Hydroponics
recommends using an 18 hours on/6
hours off lighting schedule. In
order to induce your plants to
flower we recommend subjecting
your plants to a 12 hours on/12
hours off lighting schedule.
Is it OK to leave my lights on
24 hours per day?
HydroGrown Hydroponics does not recommend
running lights 24 hours under
any circumstances. Your plants
need a time to "rest" and grow.
This is achieved during the dark
period. Running your lights for
24 hour cycles may have a
detrimental affect on your
lighting system and your plants,
not allowing them to develop
properly. In addition, many
plant species do most of their
feeding during the night,
especially when daytime
temperatures are high or
humidity levels are low.
How do I determine how much my
electric bill will increase by
using a lighting system?
First, find out what your
electricity provider is charging
you per kilowatt hour (KWH). In
Cyprus, it's approximately €0.10/KWH, but this number will
vary depending on the total
power consumed. This number
represents what a 1000W lighting
system will cost you per hour to
run. So, if you have a 400W
system, the number to use in the
following steps would be 0.4,
for a 600W system it would be
.06, and so on. Next, multiply
this number by the number of
hours per day you plan to
operate your lighting system.
This will give you the cost per
day. Finally, multiply this
number by 30 to see
approximately what it will cost
per month.
Power
consumption Cost Example:
€0.10 (KWH cost for a 1000W
lighting system) x 12 (hours per
day) x 30 (days per month) =
€36 per month
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