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There are many different types of lighting systems on sale, and it would be easy to get confused not knowing which lights you need. Each stage of growth requires different lighting and the wrong choice can make a great difference. Here I will briefly describe some lighting types and their functions, but I won't go into all the technical jargon associated with indoor lighting, as space is limited and I don't want to bog you down with too much technical data. (There are plenty of books and web sites out there that can do that). For your benefit we will keep it simple and go over only what's relevant. Then when it comes to the setting up of your indoor garden, you'll understand why you need to use specific light systems and lamps.

Most H.I.D (a generic term, High Intensity Discharge) grow lights are either vertical or horizontal reflector systems which are mounted separately from the remote power boxes (ballasts or control gear) that actually strike the lamp. They are remote because they can be kept away from the growing area, which is a good safety aspect, as well as reducing the heat in the growing area.

Whether you purchase a horizontal or a vertical reflector again depends on the size and shape of the area you wish to use. The horizontal reflector is used in a rectangle shaped area and the vertical reflector generally is used in a square area. All of these reflectors are designed to better focus the light at the plants and are available in numerous designs. Remember, the idea is to create as near as possible the exact light needed for plant growth.


There are many types of lamps used in lighting up indoor plants, from fluorescent tubes through to H.I.D intensity lamps, (H.I.D lamps have an arc tube in the centre of an external glass jacket). The arc tube is filled with either metal halide or high pressure sodium particles. These need to be fired or struck by a very high voltage, and this is done by way of a ballast or control box. In the ballast box is a choke, ignitor and a capacitor all of which work together in starting the lamps. Conventional lamp fittings like we have in our own homes will not do this, so don't try!!

H.I.D lamps come in power ranges from 150W up to 1,500W. Not all similarly powered lights are of the same quality, and beware that some manufacturers claim their lights are the best, (well they would wouldn't they?) Unfortunately there are so many on the market at the moment that knowing which one is right for the job is hard to sort out. All these lights also need to have reflectors, which play an important part in plant development by pushing or directing the light down to the desired area.

There has been considerable debate in the past over whether metal halide or sodiums are better suited to indoor plant growth. A lot of the the data available can be a bit contradictory, but it is my view that results speak for themselves, so I would suggest you stick with what works and is used most widely by the industry.

I will take you through the main types used and what job they are used for in indoor plant growth:

Fluorescent tubes
These have been used for seedlings, tissue culture and cuttings for a great number of years and the most commonly used is the Sylvania Grolux tube. By using fluorescent tubes to achieve mature growth, plants must be grown as close to the tube as possible without touching the tube, as this may cause burning of the plant tissue. The closeness of the tubes is required as each tube only outputs the minimum light required for plant growth and if placed further away from the tube the output of the light diminishes. Always use a reflector housing, as this will direct the light towards the plant rather than away from it. This generally increases the light to the plants by 50%.

The benefits of fluorescents are low initial purchase price of the fixture, and the low running costs, however the negatives are that the plants will have smaller internodal lengths, smaller leaves and smaller flowers. Plant growth may also be slower than expected so as a general rule fluross is they are only used in the propagation stage of a plants growth. You would require a lot of fluorescent tubes to get a good result in the flowering stage.

Metal Halides
These lamps can be used to grow and flower an indoor garden, although most growers use these bulbs to vegetate their indoor garden only. When they decide to initiate flowering they use a high pressure sodium to flower, or a mix of both. Metal halide lamps are available in 400, 600, 1000 and 1100W versions. They emit a blue/whitish light to the eye and are used for increasing the plant's growth rate during vegetation. Metal halides are ideally suited to any indoor application where you want healthy vegetative growth and large bushy plants.

Retro fit lamps

Retros were produced to run on opposing control gear, meaning you could effectively run one light fixture and change from metal halide to high pressure sodium when you wanted to flower. They are available in 150W right through to 1000W, although the 1000W version is extremely power hungry and has a high mortality rate! They are available in both types, either high pressure sodium (HPS) or metal halide (MH).

The HPS retro lamps don't have the intensity or lamp life of the normal HPS lamps. The reason for their use was due to the fact that metal halide control gear is cheaper to produce and runs at a slightly lower amperage than HPS ballasts. The metal halide retros are available in 400 and 600 watt and are used mainly in situations where growers want to mix light but don't have to change control gear to get a little bit more of the blue or vegetative end of the spectrum. Retrofits provide an economical alternative to growers who need a distinct light spectrum when required. Remember, without a retro lamp you must marry up a metal halide lamp with a metal halide ballast and visa versa, high pressure sodium lamps with a high pressure sodium ballast.

High pressure sodium

HPS bulbs are used during the flowering cycle of plants and are rich in the red end of the spectrum and to the eye they emit an orange/yellow light. HPS lamps will give you much tighter and thicker flowers than a metal halide and are available in sizes from 150 to 1000W. There are some manufacturers who have now put more of the halide particles into HPS lamps which increases the blue spectrum slightly, consequently many growers will vegetate as well as flower under these. They are the preferred light source for growers who want to vegetate as well as flower their plants under one light source. It really depends on how you want to run your garden as to what light to use and when.

Sunmaster 1100W metal halides

These lamps are the latest technology in lamp manufacture and in my opinion are the best light source for your indoor plants. I have seen all the of lamps in action in all sorts of different venues with different growing systems and techniques over the years and I believe the 1100W out performs all of them across the board. It has been designed specifically for plant growth to give the grower the best all round quality of light for the intended job. Their high intensity and colour spectrum are second to none in efficiency and they can penetrate the leaves and light up the whole plant more effectively than any other light source. This means thicker and faster growing plants. They are strong in all the colours of the spectrum and they promote strong healthy vegetative growth. In flowering they keep internodal spacing close hence flower formation is at a premium and therefore yields are enhanced due to the broad spectrum of colour and intensity the plant is receiving. Given also that the 1100W light package is the same price if not a bit less than most 1000W kits it would seem the logical choice for the indoor grower who wants to light up more than a square metre.

See our Specification Chart which will give you all the specifications of various lamps and control boxes used for growing indoors. The above dollar values in power consumption are based on N.S.W rates but they would be close to the mark in other states.

In the above chart I have also listed both lumen and par watt ratings of various lamps. Depending on which you adhere to, a brief explanation of both is warranted. Lumens are based on the eye sensitivity curve of human beings not plants, and although it has long been recognised as the standard measurement for plant light intensity, this is not truly correct. PAR (Photosynthetically Active Radiation) watts on the other hand objectively measures the total watts emitted by the lamp which actually accounts for the nutritional value of the light energy available for the photosynthesis process of plants.

The average effective growing life of most horticultural lamps is not necessarily what is stated on the packaging. Manufacturers base lamp life on the total life expectancy, which can be misleading to the indoor grower. A lamp has a natural mortality curve which dips dramatically when it reaches 60% of its life. How do you work it out yourself you say? If you don't have a light meter to test intensity, then the only way is to date each lamp when you put them in. It has been my experience that it will soon show in the plant when your lamps need replacing because they will suddenly start to stretch and have long internodal spacings as a result of trying to absorb more light. Ultimately this will end up giving you very low yields as well as more plant problems like disease and pest infestations. Why you say? Because the plant is not strong enough to deal with them, and this is due to its inability to absorb light needed to produce all the essential sugars. By increasing the light intensity, the ability of the plant to manufacture more of the these sugars is boosted and therefore it is able to repel bug or fungal infestations much more effectively.

The average effective growing life of HPS lamps running on a 12 hour cycle are; 9 months for a 400W hps lamp, 12 months for 600Wt lamps, 16 months for 1000W lamps. If using an 18 hour veg (2 weeks) and a 12 hour flowering (6 week) regime, it would work out at 3 crops for a 400W, 4 crops for a 600W and 6 crops for a 1000W. If running 1100W Sunmaster metal halides I would follow the 1000W path in terms of when to change. For those of you who think they can run lamps longer I suggest you plot yields as well as problems that develop as most drops in yield and problems with bugs occur later in the lamp's life. Change lamps or pay the price in lower yields.


Figuring out what light size you need is closely coupled to the power needed to run them. It's obvious that the larger the garden the more it will cost to run, the reason being that a large garden will need more light. The running costs of a 400 watt light is approximately $0.04 cents for every hour of operation. With HID lighting, if a 12 hour day is used, this will equate to about $3.00 a week. An 18 hour day would be $5.00 per week.

MOUNTING HEIGHTS - we recommend placing your lights at the mounting heights listed below as this will give you the best coverage and light intensity for optimum indoor plant growth rates.

Vertical - 400 watt coverage 900mm x 900mm mounting height 300mm from top of canopy. Horizontal - 400 watt coverage 900mm x 600mm mounting height 500mm from top of canopy.

Vertical - 600 watt coverage 1200mm x 1200mm mounting height 600mm from top of canopy. Horizontal - 600 watt coverage 1200mm x 800mm mounting height 800mm from top of canopy.

Vertical - 1000 watt coverage 1800mm x 1800mm mounting height 900mm from top of canopy. Horizontal -1000 watt coverage 1600mm x 1000mm mounting height 1000mm from top of canopy.

Vertical - 1100 Watt coverage 1800mm x 1800mm mounting height 1000mm from top of canopy. Horizontal - 1100 Watt coverage 1800mm x 1200mm mounting height 1100mm from top of canopy.

You can go closer to the plants if you wish, however be aware of heat problems around the canopy. This will show up on the plant in the form of leaves curling upwards and browning of the leaf tips. If this occurs, move lights away immediately. Monitoring temperature and humidity is also essential. If the temperature (27deg.c) or humidity (70%) is achieved it would be advisable to reduce the stress on the plant by raising the light and lowering the nutrient concentration. If you find it uncomfortable in the grow room I would say your plants do too!

Finally, some important words about lighting. I have mentioned before, and I can't stress this point enough, that during the dark hours the flowering chamber must NEVER be opened allowing outside light to get in. This is especially important during the first two weeks. NEVER, (unless you want to do some real damage), let so much as even a flicker of light get to the plants. Even a lit match or lighter is a major stress to the plant. The reason for this is that plants constantly produce a flowering hormone call PHYTOCHROME which helps the plant develop flowers rather than leaves and exposure to light during the dark period will stop this hormone from working, and supress the development of flowers.