Light is the single most important thing for you to consider. Obviously, if you wish to grow marijuana plants in your coal cellar for instance you will have to provide all the light yourself and you will need to provide a lot if you are to recreate the conditions of a summer's day. Fortunately, modern horticultural lighting is more than capable of doing this in an efficient and cost effective manner. One can start by assuming that you have no natural light whatsoever in your chosen growing area. Obviously, if you have a window or skylight, this will reduce the amount of light that you have to provide but in most cases, this is not especially significant. There are other problems associated with using natural light such as the inability to control the hours of darkness. The easiest and most efficient way to grow marijuana plants indoors is to do it in a dark area and provide all the light yourself. For greenhouse growers, the need to use extra light is limited to the darker months of the year. Another thing to consider under the heading of light is the level of reflection in your growing area. A well designed cannabis growroom will get the maximum benefit from the light that is used in it and it is of great importance to get the best reflection of available light.
Temperature is another important design parameter of your marijuana growroom and it is something that must be borne in mind from the beginning. Most marijuana plant species will grow most effectively in the temperature range of 68 to 83°F | 20 to 28°C, the mid twenties being optimal. It will not be difficult to maintain this sort of temperature in your room while the lights are on as they are a great source of heat as well as light. If temperatures should become too high, a simple extractor fan should serve to reduce them. This extractor can be easily linked to a thermostat to ensure that your room never reaches the high temperatures that can have a negative effect on growth rates. When your lights are off, however, you will expect a gradual decline in temperatures. In the colder parts of the year, they will drop well below the ideal growth range. Recent research has shown that night cycle temperatures are just as significant as day cycle temperatures in marijuana plant production and it is in fact the relationship between them that has most effect on the final shape and productivity of the marijuana plant. It is important to avoid large temperature fluctuations between the day and night cycles as this can lead to weak and poorly formed marijuana plants. It is ideal for most species to try and bring day and night temperatures as close together as possible and this is not as difficult as it sounds. The most effective way to do this is to install a propane heater in your room and ensure that the thermostat is set to come on when temperature falls below 68 °F | 20°C and to go off at around 86 °F | 30°C.
This device will work in perfect harmony with your lights which are the other source of heat in the room and the extractor to maintain a constant temperature in the mid twenties. The added bonus of a propane heater is that it will produce copious quantities of carbon dioxide, the "growth" gas that will have an amazing effect on marijuana plant growth. One of the cheapest and most important pieces of equipment in the growroom in the maximum-minimum thermometer. This should always be placed amongst the plants and consulted and reset daily. It will tell you the highest and lowest temperatures reached during the previous 24 hours. Once you are established, it will be a simple matter to adjust your equipment to maintain the even and constant temperature that you are aiming for. If the maximum temperature is getting too high you adjust the thermostat or timer on your extractor. If the minimum temperature is getting too low, you adjust the thermostat on your propane heater. The whole principle of indoor gardening is about control of the environment. This is your chance to tame the weather and the extra effort will be well rewarded by your results. An even better way of monitoring your growing environment is with a thermo-hygrometer. It can be switched on and left in the growing area for a period of 24 hours or longer. It gives clear and accurate readings of both temperature and humidity and it will also tell you the maximum and minimum levels of temperature and humidity over a given period. This is essential information for the serious grower.
Humidity is another important consideration in cannabis growroom management. If it is allowed to get too high for prolonged periods, it will cause problems both in your room and amongst your marijuana plants. The main danger is the development of Botrytis or grey mould. This organism thrives in conditions of high humidity and will quickly spread and ruin a crop. The cautious marijuana grower will always monitor the humidity in his growroom which is measured by another simple device called a hygrometer. This is a dial type instrument that can be mounted on the wall next to the maximum-minumum thermometer and give a constant and accurate reading of humidity. The ideal humidity for a marijuana plant raising would not be much above 50%. If it rises above this, the grower will normally operate his extractor fan until it has been reduced. To keep this potential problem under check, it is advisable to avoid leaving water on the floor which can then evaporate and raise humidity. Any water or nutrient solution that spills or overflows should be wiped up promptly and nutrient tanks should be covered at all times. Any water that is left exposed to the heat from your grow lights will rapidly evaporate and add to the humidity levels. Keep your greenhouse or growroom dry.
The fourth variable that needs to be taken into account at the design stage is the atmosphere or air in the growroom and it is here the marijuana grower is often faced with a dilemma. On the one hand there is a strong requirement for a continuous supply of fresh air. Growing marijuana plants need a constant supply of carbon dioxide [COČ ] to maintain growth. COČ is present in normal fresh air at the rate of around 330 parts per million [ppm]. If you try to grow marijuana plants in a closed and sealed room you will quickly run into problems. As the marijuana plants grow they will rapidly use up the available COČ which can drop to less than a third of normal levels within one hour. At this point marijuana plant growth will effectively cease. To maintain normal atmospheric levels of this essential gas, the marijuana grower would be advised to run an extractor continuously as well as providing an input point, such as an open door or window, for the fresh air to enter the room. The problem with this of course is that the extractor will reduce temperatures and the marijuana grower may not wish to run it any more than necessary to maintain temperatures in the desired zone. It may also not be convenient to leave a door or window open on a long term basis. Fortunately, modern technology has provided simple answers to the marijuana grower's dilemma as carbon dioxide [COČ ] can be added to the atmosphere in the marijuana growroom which reduces the need for fresh air being brought in. COČ can be introduced from bottles which can be produced by burning propane.
Gas from bottles
CO² is readily available anywhere as it has many uses in the food industry including the pressurization of beer kegs. This bottled gas is available in various sizes and the medium size is easiest to handle; avoid the largest ones particularly if you have to take them upstairs. It may be possible to get your gas in aluminum cylinders which are much lighter to handle. Once you have your gas bottle you will need a regulator to control the amount of gas that enters the room, once again technology has the answer. There are various regulators and controllers that have been developed to provide simple CO² injection for the amateur and professional gardener alike. These simple and efficient units will inject CO² into the greenhouse or growroom.
Growth gas generator
This is a dedicated carbon dioxide production unit designed specifically for the small domestic greenhouse or indoor growing area. It burns readily available propane gas to produce carbon dioxide in copious quantities. Growth Gas Generator is controlled by an electric solenoid and can be simply plugged into a timer. This means that the marijuana grower can easily set his generator to provide CO² during the hours of brightest sunlight when plants can best utilize it. Generator can also be used with CO² sensors to maintain precise levels in the hi-tech growing environment. Growth Gas Generator is provided with suggested timer settings to provide optimum CO² levels in any area up to about 141 square foot | 43 square meters. It is designed specifically for gas production rather than heat. Heat production is kept to a minimum for the volume of gas produced. The Growth Gas Generator is constructed from high grade stainless steel and is designed to last for many years in the humid environment of a greenhouse or growroom. Growth Gas Generator is not a greenhouse heater. Greenhouse heaters are designed to produce heat, and carbon dioxide is merely a by-product. As they are thermostatically controlled they will produce more gas as the temperature drops. Unfortunately, this means that most of the CO² is produced at night when plants cannot make use of it. Growth Gas Generator is designed to produce CO² and can be set to produce it during the daylight hours. While it is a minimum requirement for good growth that CO² should be in the range of 300 to 350 parts per million [ppm], it is possible to provide it at much higher levels. Modern research has shown that levels up to 1500 ppm and beyond can be maintained in a growroom and that plants will respond amazingly well provided that they have adequate light, moisture and nutrition to enable them to take advantage of the conditions. The serious grower who couples the power of modern horticultural lighting with the simple science of hydroponics and the benefits of enhanced CO² can achieve growth rates and yields that were only dreamt of a decade ago.
Measuring CO² levels
Until recently, there was no simple way for the amateur marijuana grower to measure the CO² levels in his greenhouse or cannabis growroom. It was only professionals that had the necessary equipment. Nowadays it is an easy matter with the CO² analysis kit and there is no reason for the grower to rely on guesswork any more. CO² detection is easy with the pump action analyzer syringe and analyzer tubes measuring 300 to 5000 [ppm]. Quick measurement of CO² in the growroom will tell you if your environment is optimized. Supplied with full instructions, the kit is quick and easy to use and it will give you a reading in parts per million [ppm]. The careful marijuana grower will treat CO² as one of the most important elements in a successful growing area. It is not an difficult matter to optimize the levels and the dramatic improvement in plant performance and yields will certainly make the effort worthwhile.
The final thing the marijuana grower will consider is the installation of a negative ion generator in the greenhouse or marijuana growroom. This is an unobtrusive device that costs little to buy and less to run. Negative ions freshen and revitalize the air with very low running costs and removes dust, cigarette smoke, pollen and bacteria. This appliance cleans the air of pollutant particles while creating billions of negative ions which freshen and revitalize the air. Negative ions have proven effects on marijuana plant growth and will have a positive effect on yields and quality. They will also help to eliminate unwanted foliage smells in your house.
This is a huge topic and way beyond the scope of this fact sheet. We can however, focus on some of the pest problems most commonly encountered in the small greenhouse or indoor marijuana growroom. The control of plant pests has always been a contentious issue and we would assume that the majority of serious growers would like to avoid the use of toxic chemicals wherever possible. Like every other aspect of marijuana plant raising, there have been many changes in recent years. These have been tested and fine tuned by professional growers and are now becoming available to the amateur marijuana gardener. Amongst the new technologies, the idea of biological pest control must take pride of place. Like all great concepts, it is simple yet effective and is causing major changes to the way we do things. Biological pest control is one of the most exciting developments in modern horticulture and it offers a vision of a pesticide free future when man can use nature's own weapons to grow his food in an uncontaminated atmosphere and a cleaner, greener world. Basically, biological pest control involves the introduction of friendly creatures to combat the ones that do the damage. These creatures are known as predators because they feed on the pest at some stage in its life cycle. Here are two examples:
Two spotted Mite [Spider mites]
These little creatures, almost invisible to the naked eye, are undoubtedly the greatest menace to the marijuana grower. They are often unseen and unsuspected until their numbers are high and they can multiply at a devastating rate. If they find favorable conditions in the greenhouse or indoor marijuana growroom they can literally destroy a crop. The first signs of their presence are small dead spots that appear in clusters on the affected leaves. This is followed by a general bronzing of the foliage and as the infestation increases, there will be visible deposits of fine webbing on the underside of leaves. Old fashioned methods of chemical control have never been successful for long as these creatures are very adept at developing resistance to each poison in turn. Man has responded by using ever more toxic chemicals to control them with an ever decreasing success rate. The side effects of this are the collateral destruction of hundreds of beneficial or neutral insects that would normally co-exist with the mites in some sort of balance. The solution that biological pest control offers is the introduction of another mite called "Phytoseiulus Persimilis" which lives exclusively on two-spotted mites. If the population of pests is at a high level, the predator will multiply in relation to its food supply. Once the pest is reduced then the predator will begin to die out as well. A balance should then be achieved which will maintain the pest population at low levels, below the point at which they will cause visible damage. If the pests do begin to multiply beyond the predators' capacity to consume them, the marijuana grower can then make small adjustments to the environmental conditions [temperature and humidity] that will favor the predators over the pests. Predator mites are known commercially as "Spidex".
Most marijuana gardeners will be familiar with these little flies that fly up in clouds when you disturb the affected foliage. They are a major pest of the commercial greenhouse industry and they can cause just as much damage in a hobby greenhouse. Once again, the chemical approach has failed utterly to control them and breeders of biological agents have come to the rescue. The predator of whitefly is a tiny wasp called "Encarsia Formosa". This minute wasp is totally harmless to everything but whitefly. It bears no resemblance to wasps as we normally think of them but resembles a fruit fly, only much smaller. Encarsia is totally dependent upon whitefly for reproduction as it lays an egg in the whitefly larvae which then becomes the food source for the developing larvae of the wasp. This process effectively replaces a whitefly with a wasp which can then go on and lay more eggs. This predator of whitefly is sold under the trade name of "En-Strip".
More information about Cannabis pests