Cannabis Growing Indoor
Indoors
Indoor growing allows the gardener to exercise complete control over the growing environment. Length of day, levels of light, temperature, humidity and nutrient are all adjustable. Arguably the best varieties are bred for indoor growing. You may need hydroponic equipment.
Setting up an indoor growing area
Planning
A space as small as the average wardrobe will provide enough bud for personal use (including a few friends). Heavy tokers may want to create a larger growing area - the following method can be scaled up to virtually any size.
Plan the grow room carefully before you start construction. Ask yourself a few questions:
Have I got access to several 13A sockets?
Can I get water to the grow room easily?
Will anyone be able to see light spillage?
Will anyone be able to hear the ventilation fans?
Will anyone be able to smell the plants (it's not called skunk for nothing!).
What can I do if I want to go on holiday?
Tell nobody about your horticulture. www.theairsoftshop do not keep mailing lists.
Creating a space
Find a suitable sized wardrobe or cupboard. If you want something bigger, construct a box with roughcut timber covered with plywood, chipboard or plasterboard. The box could extend from floor to ceiling, giving the impression that it is an integral part of the structure of the house.
The floor of the growroom should be some sort of waterproof tray - if you bring down the ceiling of the flat below, awkward questions will be asked! The floor (wardrobes and cupboards) should be strong enough to support the weight of your plants, pots and water-soaked compost.
Make a door big enough to allow easy access to the plants and equipment inside. You could try disguising the door of a floor to ceiling box such that it is not obvious that the growing room even exists!
Line or paint the room with something reflective; matt white seems to work better than a mirror finish. Remember that the inside will have to be cleaned periodically to remove dust, compost, mould and algae.
Ventilation
Ventilation is very important; plants need CO2 for photosynthesis and the temperature and humidity must be kept to an acceptable level. Louvres at the top and bottom of the space will sometimes be enough but it is better to arrange for some forced ventilation. Electronics shops like Maplin or Tandy sell 240v fans for around £15. Fans need to be kept running 24 hrs/day irrespective of the length of lighting period. If you can, take the fan exhaust through an outside wall to reduce the smell. Some growers report that an ioniser operating near the exhaust end of the air vent reduces the smell considerably.
A circulating fan inside the room is desirable but not essential*.
Heating
For healthy growth, the temperature needs to be maintained at 15C to 30C. Cannabis will tolerate temperatures as low as 5C and as high as 40C but these do not represent ideal growing conditions.
If your grow room is in an otherwise unheated area (like a cellar or garage) you will need to install some sort of electric heating controlled by a central heating thermostat.
Lighting
The type of lighting used depends on the size of room and the type of growing method. Indoor growing requires the light intensity, ideally, to be between 2000 and 3000 lumens/sq. ft.
Tungsten filament bulbs are very inefficient and produce more heat than light; some sort of gas discharge lamp is required. There is much debate about the relative merits of the various types: fluorescent tubes, mercury vapour, metal halide and high pressure sodium. Mercury vapour and metal halide are useful during the vegetative growth stage; HPS are perfect for flowering and acceptable for vegetative growth; fluorescent tubes are general purpose. In the writers opinion, only fluorescent tubes and HPS need be considered as other types involve a change of lamp when the flowering stage is induced.
Fluorescent tube systems
Fluorescent tubes and their fittings are available in a range of lengths. Longer tubes obviously emit more light than short ones. Standard 1in diameter halophosphate tubes are rated at about 30 watts per metre and output about 2,500 lumens per metre (and 85 lumens per watt). Tubes are available in a range of colour temperatures: 6000K (daylight), 4000K (cool white), 3500K (white) and 3000K (warm white). Daylight tubes have more blue in their spectrum and warm white more red. Results are not much different whatever tubes you use but, if you have the choice, either use a mix of warm white and cool white or change from cool to warm white when the flowering stage starts. A quick calculation reveals that to achieve 2000 lumens per sq. ft you have to virtually cover the entire area of the room's ceiling with fittings. The fittings can get quite hot, so allow a space between them for air to circulate.
The light intensity drops quite dramatically as you move away from the tube; in fact, intensity falls with the square of the distance such that the intensity at two feet distance is one quarter the intensity at one foot. This means that plant growth is only really luxuriant up to a few feet from the tube. Fix the tube fittings to a board which is, itself, attached by cords or chains to the ceiling; this way the tubes can be kept as close as possible (a few inches) to the top of the plants. The board will have to be moved daily when the plants are growing well.
Fluorescents are most useful in situations where you are not growing the plants very tall. For instance, as a light source for cuttings (clones) or for the "sea of green" method.
HPS systems
HPS lamps are available in 150W, 250W and 400W sizes. The lumen output is, respectively, 15,000, 28,000 and 50,000. This amounts to between 100 and 125 lumens per watt, according to the size of lamp. Their colour temperature is quite low at between 2000K and 3000K; they emit a pinkish, golden white light which is similar to autumn daylight. Note that recently, a new type of HPS lamp has been introduced, the SON-T Agro, which has an extra 8% blue light added to the spectrum making it more acceptable for vegetative growth than the standard SON-T*.
There are several advantages to HPS lamps:
The efficiency, in terms of lumens per watt, is high.
There is usable light at a greater distance from the bulb, compared with fluorescent tubes.
In most domestic installations, there are only one or two lamps to change as opposed to maybe twelve or more fluorescent tubes.
Lamps have a long lifetime of 20,000 hours or more (although the output drops, gradually, during the life of the lamp - it's best to change them after one year's use).
The disadvantages are:
The cost of an entire system comprising control gear, lamp and reflector can be several hundred pounds.
The colour temperature is not ideal for vegetative growth although most growers report acceptable performance.
HPS lamps should be kept at least 18" from the plants to avoid leaf scorch or even fire! Water should be kept well away from the lamps as they can explode if splashed.
Timers
The lighting system needs to be switched automatically so that the plants receive 18 hours of light per day during vegetative growth and 12 hours per day when flowering.
Stores such as Currys and Argos sell timers, which plug in to an ordinary 13A socket, for less than £20. They claim to be able to switch 13A but inductive loads such as HPS lamp ballasts can burn the contacts quite quickly. Use the timer to operate a mains relay with a higher current rating, e.g. 30A.
For larger or more permanent installations use a surface mounted timer such as those used in central heating systems. These may have more than one timed outlet which may be useful if you are operating a two shelf "sea of green" setup.
Safety
Keep electrical circuits well away from water. Make sure that electrical wiring is installed following all the conventions used by the professionals, i.e. use cable of the correct current rating, use the correct rating fuses and earth all metal components (like control gear boxes) that could be touched.
Keep anything flammable away from hot lamps.
If you can arrange it, fix a switch near the front door which acts as a master control switch for the whole grow room's systems. If you have a visit from the landlord or the boys in blue then you can shut down the lights and fans easily before anyone hears or sees anything suspicious.
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