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Lighting Your Greenhouse

By: Dr Gareth Evans - Updated: 26 Sep 2012 | comments*Discuss
Supplementary Lighting Growing Lighting

If you plan on using your greenhouse all year round, sooner or later you will have to think about getting some lighting for it and with the wide array available – not to mention their equally large range of prices – it can sometimes be very difficult to know which to pick. Fortunately, there are a few simple factors to consider which should help to make that choice much more straightforward and the first question to ask is what sort of greenhouse do you have and what do you want to do in it?

Types of Lighting

Greenhouse lighting falls into two general categories – supplementary and growing. Supplementary lighting is designed to provide general illumination to give you enough light to work when it is going dark, as well as contributing a little towards supplementing natural daylight or artificially increasing day length during the winter or spring. Growing lighting, by contrast, is specifically intended to bring on plants – often being used to “force” them to flower out of season. As a result, it is typically more sophisticated and the quality of light produced is much more closely controlled than you need simply to avoid stumbling in the dark.

The type of lighting you need is principally dictated by whether you are simply interested in pottering about in the depths of winter, for instance, or intend to provide the perfect growing conditions for your prize orchids.

Options for supplementary lighting range from domestic incandescent bulbs and fluorescent strips to solar powered units, which can be invaluable for greenhouses on allotments or other sites where there is no mains supply – quite apart from being a very eco-friendly approach.

Growing lights start at fairly modest cost for units such as the 15-watt “Lumino”, intended for a small group of plants, while at the other end of the scale, there are systems aimed at the commercial grower with an impressive specification and an even more impressive price tag. However, it is not necessary to spend a fortune to achieve professional quality light in the amateur greenhouse, since there are several smaller units on the market which are well-featured and affordable. For a little over £70, you can purchase small scale mercury lighting systems which are ideal for forcing rapid plant growth, while for around twice as much, you can obtain high pressure sodium lamps, which tend to have a longer life-expectancy in use . A wide range of reflector units, timers, controllers and other accessories are available, allowing you to create a highly customised system to meet you own needs.

Do Your Research

Whether it is supplementary or growing lighting that you need, it is important to take into account both the heat produced and the electrical efficiency of the lights. Low energy bulbs typically produce around 80 per cent less heat than their conventional counterparts – which may be a significant factor, depending on the type of plants you are hoping to grow. Moreover, running a low-energy bulb rated at 20 watts rather than its conventional 100-watt counterpart, over several hours of the day throughout late autumn and winter will certainly make a difference to your electricity bill. Finding out the heat and power figures for each possible option is an important part of the research to be done before buying.

If you are buying growing lights, it is important to have a very clear idea of the purpose they will be put to – and ensure that the lamps output, both in quantity and quality of light it produces, are suitable. Some lamps, for instance, produce more light of particular colours – perhaps red or blue – and this can have a significant effect on plant growth. Lighting can be a make-or-break factor in a plant’s development, particularly for some exotic or speciality varieties, so it is worth taking the time – and asking for some expert advice, if needs be – to get it right.

Being able to control the lighting in the greenhouse is every bit as important as controlling temperature, ventilation and humidity. Light has a remarkable effect on plant growth – and most particularly, on flowering. Gaining the ability to manage it artificially gives the grower the potential to produce displays out of season, while even the simplest form of supplementary lighting extends the enjoyment to be had in the greenhouse – and stops us having to stumble about in the winter’s gloom.

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