Grow light


 

light

 

 Dual spectrum compact fluorescent grow light. Actual length is about 40cm.A grow light is an electric lamp designed to promote plant growth by emitting an electromagnetic spectrum appropriate for photosynthesis. The emitted light spectrum is similar to that from the sun, allowing indoor growth with outdoor conditions. Natural daylight has a high color temperature (approx. 6000°K) and appears bluish. Through the use of the color rendering index, it is possible compare how much the lamp matches the natural color of regular sunlight.

Contents grow lights
1 Light spectrums used
2 Types & set-ups
2.1 Incandescent grow lights
2.2 Fluorescent grow lights
2.3 Metal-Halide (MH) HID grow lamps
2.4 High-pressure sodium lamps
2.5 Combination HPS/MH lamps
2.6 Switchable, convertible & two-way lamps
2.7 LED grow lamps
3 Use
4 Light requirements of plants




grow lights Light spectrums used

The light spectrums of different grow lampsDifferent light spectrums are used for the different stages of plant growth. The initial vegetative stage requires blue spectrum of light, whereas the later 'flowering' stage is usually done with red/orange spectrums. The lights can be bought by spectrum colour specifically, or some companies such as Sylvania Grolux produce a full spectrum bulb which caters for all stages of growth.

The light is usually used in conjunction with a reflector, to control and intensify the light emissions, and will include an electrical ballast to control the flow of current flowing to the light. This is required because of the high intensity of the light that is necessary to produce something akin to sunlight.


grow lights Types & set-ups
Lamp types used as grow lights include incandescents, fluorescent lamps, high-intensity discharge lamps, and LEDs.

Today, the most widely used lights for professional indoor flower and vegetable growing are HPS/SON (high pressure sodium) and MH (metal halide). These are types of HID or high-intensity discharge lamps. MH is used for vegetative phase of growth, as it encourages short internodes (distance between sets of leaves), and inhibits cell elongation, creating a shorter, stockier plant. Unlike high pressure sodium lamps, metal halide lamps also produce ultraviolet radiation, which may play a role in increasing the amount of THC produced by the plant. High pressure sodium lamps trigger a greater flowering response in the plant and are thus used for the for the second (or reproductive) phase of the growth, or they are used by those people who only wish to purchase 1 single lamp. [1] If high pressure sodium lamps are used for the vegetative phase, plants will usually grow slightly more quickly, but will also have longer internodes, and may be taller. [2]


grow lights Incandescent grow lights
Incandescent grow lights have a red-yellowish tone and low color temperature (approx. 2700°K). They are solely used to highlight indoor plant groupings and not as a true plant 'growing' light (aldough they may be labeled as such). Incandescent growing lamps have an average life span of 750 hours.


grow lights Fluorescent grow lights
Today, (HID) lights are available in any desired color temperature in the range from 2800°K to 6000°K. Standard fluorescents are usually used for growing vegetables (as leaf lettuce, spinach, and herbs) or for starting seedlings to get a jump start on spring plantings. Standard fluorescents produce twice as many lumens per watt of energy consumed (compared to incandescents) and have an average usable life span of up to 20,000 hours. This is 25 times as long as an incandescent. Cool white fluorescent lamps are sometimes used as grow lamps. These offer slightly lower performance, a white light, and lower purchase cost.

High Output fluorescents produce twice as much light as standard fluorescent lamps. A HO fluorescent fixture has a very thin profile, making it extremely useful in vertically limited areas. High Output Fluorescents produce about 5,000 lumens per 54 watt bulb and are available in warm (3000°K) and cool (6500°K) versions. Usable life span for High Output fluorescent lamps is about 10,000 hours.

Compact fluorescents are smaller versions of fluorescent lamps and are used for propagation, aswell as for growing larger plants. Compact fluorescents work in specially designed reflectors that efficiently direct light to the plants, much like the HID lamps below. Compact fluorescent bulbs are also available in warm (3000K) and cool (6500K) versions. Usable life span for compact fluorescent grow lamps is about 10,000 hours.

High Output Fluorescent/HID hybrids combine cool burning with the penetration of high intensity discharge technology. Primary advantages to these fixtures is their blend of light colors and broad even coverage.


grow lights Metal-Halide (MH) HID grow lamps
Metal halide HID lamps deliver a white light in the range of 2700 to 5500° Kelvin with a color rendering index of 65-75. As such, plants growing under most metal halide lamps appear almost identical to those growing outside. They are used where color rendering is important such as stadiums, malls, manufacturing plants, and supermarkets. Metal halide lamps are five times more efficient than incandescent lamps and last up to 25 times longer, with a usable lifespan between 10,000 and 20,000 hours, depending on the wattage. Horticultural metal halide lamps have an enhanced red spectrum, which is added for increased fruiting and flowering.


grow lights High-pressure sodium lamps
high pressure sodium lamps yield yellow lighting (2200K) and have a very poor color rendering index of 22. They are used used for the for the second (or reproductive) phase of the growth. If high pressure sodium lamps are used for the vegetative phase, plants will usually grow slightly more quickly, but will also have longer internodes, and may be taller.They are used in less color critical applications such as parking lots, street lights and for supplemental greenhouse lighting. The benefit of high pressure sodium lamps to the horticultural industry is their ability to enhance the fruiting and flowering process in plants. Orange/red spectrum HPS produces is the spectrum plants use in their reproductive processes, which generally produces larger harvests of higher quality fruits or flowers.Plants grown under high pressure sodium however yields taller and leggier plants with a longer internodal length than plants grown under the bluer light of metal halide. Also, the plants grown under these lamps do not appear very healthy (aldough they usually are).This is due to the poor color rendering of high pressure sodium, which makes the plants look pale, washed out or nitrogen starved. Benefits to high pressure sodium lighting are their incredibly long usable bulb life (up to two years in many cases); and unparralled efficiency at six times more light output per watt of energy consumed than a standard incandescent grow lamp. Due to their high efficiency and the fact that plants grown in greenhouses get all the blue light they need naturally, these lamps are the preferred supplemental greenhouse lights.


grow lights Combination HPS/MH lamps
Combination HPS/MH lamps combine a metal halide bulb and a high pressure sodium bulb in the same reflector, either with a single integrated ballast assembly or two separate ballast assemblies. The combination of blue metal halide light and red high pressure sodium light creates an ideal spectral blend and extremely high outputs.


grow lights Switchable, convertible & two-way lamps
Switchable, Two-Way and convertible lamps are used to burn either a metal halide bulb or an equivalent wattage high pressure sodium bulb in the same fixture, but not at the same time. These fixtures are used for propagating and vegetatively growing plants under the metal halide, then switching to a high pressure sodium bulb for the fruiting or flowering stage of plant growth. To change between the lamps, only the bulb needs changing and a switch needs to be set to the appropriate setting.


grow lights LED grow lamps

LED panel light source used in an experiment on plant growth by NASA. Pictured plant is a potato plant.Recent advancements in LEDs have allowed for the production of relatively cheap, bright and long lasting grow lights that emit only the colors of light required for plant growth. These lights are attractive to indoor-growers since they do not consume as much power, do not require ballasts, and produce a fraction of the heat of HID lamps. The lamps consist of arrays of many wide-spectrum red and a few narrow-spectrum blue LEDs of specific wavelengths. Although LED grow lights have shown promise through plant research by NASA and many universities, it is unknown whether the results are applicable to the cultivation of all plant-species, as their luminous efficiency is much lower.


grow lights Use
Grow lights are most used for indoor gardening, plant propogation and food production, including indoor hydroponics and aquatic plants. Aldough most grow lights are thus used on a industrial level, some small-scale/domestic usage of these lamps has too ben found.

According to the inverse square law, the intensity of light radiating from a point source (in this case a bulb) is inversely proportional to the square of the distance from the source. So if an object is twice as far away, it receives only 1/4 the light. This is a serious hurdle for indoor growers, and many techniques are employed to use light as efficiently as possible. Reflectors are thus often used in the lamps to maximize light efficiency. Plants or lights are moved as close together as possible so that they receive equal lighting and that all light coming from the lamps wind up on the plants (rather than partly besides it). Often, the distance between lamp and plant is in the range of 24 inches (with incandescent lamps), up to 4 inches (with other lamps as compact, large and high-output fluorescent lamps)[3]. Some marijuana cultivators cover the walls of their grow-room with some type of reflective material, or alternatively, white paint to maximise efficiency.

A commonly used covering is 6 millimeter (150 µm) PVC plastic sheeting that is white on one side and black on the other. The plastic is installed with the white side facing in to the room to reflect light, and the black facing the wall, to reduce fungus and mold growth. Another common covering is flat white paint, with a high titanium dioxide content to maximize reflectivity. Mylar sheeting is also sometimes used, along with Astrofoil (which also reflects heat), and Foylon (a foil-laminated, reinforced fabric).


grow lights Light requirements of plants
To determine the appropriate lighting (and the lamp to be best used), the specific needs of the plant need to be determined. To arrange optimum lighting, the lighting present in the plant's natural environment need to be imitated. Offcourse, the bigger the plant gets the more light it requires; if there is not enough light, a plant will not grow, regardless of other conditions. [4]

For example vegetables grow best in full sunlight, which means in practice that as much light as possible must be supplied to grow vegetables indoors (fluorescent lamps, or MH-lamps are thus preferred). Foliage plants (eg Philodendron) grow in full shade and can therefore grow normally with relatively little artificial light (thus for the latter, regular incandescents may already suffice).

In addition, plants also require both dark and light ("photo"-) periods. [5] As such, lights need to be timed to switch them on and off at set intervals. The optimum photo/dark-periods is specific depending on each plant (some prefer long days and short nights an others preferring the opposite, or something in between)

For indoor gardening one of the most important topics is light density, measured in lux. Light density is the amount of light incident on a surface. One lux equals one lumen (unit) of light falling on an area of one square meter. A brightly lit office would be illuminated at about 400 lux. In Imperial (pounds-feet) terms, a foot-candle, or the intensity of a standard candle on an area of 1 square foot, is about 10.76 lux.


grow lights References
^ Cannabis Growing Guide Part 2 - Grow lamps
^ Lights - High Pressure Sodium AND Metal Halide
^ Grow lights and specing between plants
^ Determining appropriate lighting
^ Plants requiring dark and light periods

grow lights See also
Chlorophyll
Indoor plant cultivation
This article is about methods of cultivating plants indoors, growing the them in a soil-like medium and adding fertilizer when the plants are given water. Cultivating plants indoors can also be done trough the use of hydroponics; however, this method is somewhat less common [1] [2] Cultivating plants indoors is more complicated and expensive than growing outdoors, but it allows the cultivator complete control over the growing environment. Plants grown outdoors (eg cannabis) can be just as potent as its indoor counterpart if tended to properly.

Contents grow lights
1 Basics
1.1 Applying light
1.2 Arranging the right atmosphere
2 Phases of growth
2.1 Germination
2.2 Seedling phase
2.3 Vegetative phase
2.3.1 Topping
2.3.2 Pinching
2.3.3 LSTing
2.4 Reproductive/Flowering phase



grow lights Basics
To grow plants indoors, a growing medium (eg soil or growing substrate), water, fertiliser, appropriate light and atmosphere need to be applied to the plant.


grow lights Applying light
To determine the appropriate lighting (and the lamp to be best used), the specific needs of the plant need to be determined. To arrange optimum lighting, the lighting present in the plant's natural environment need to be imitated. [3] For example vegetables grow best in full sunlight, which means in practice that as much light as possible must be supplied to grow vegetables indoors (fluorescent lamps, or MH-lamps are thus preferred). Foliage plants (eg Philodendron) grow in full shade and can therefore grow normally with relatively little artificial light (thus for the latter, regular incandescents may already suffice).

In addition, plants also require both dark and light ("photo"-) periods. [4] As such, lights need to be timed to switch them on and off at set intervals. The optimum photo/dark-periods is specific depending on each plant (some prefer long days and short nights an others preferring the opposite, or something in between)

Most plants will grow under most light spectra, yet always prefer a full spectrum light. A test done by Ed Rosenthal[citation needed] found that when a room was set up using both high pressure sodium (HPS) and metal halide (MH) lamps the plants in between the two lights did better than those under MH alone but not as well as those under HPS. However, Cannabis can be grown successfully under both types of light. MH is used for vegetative phase of growth, as it encourages short internodes (distance between sets of leaves), and inhibits cell elongation, creating a shorter, stockier plant. Unlike high pressure sodium lamps, metal halide lamps also produce ultraviolet radiation, which may play a role in increasing the amount of THC produced by the plant. High pressure sodium lamps trigger a greater flowering response in the plant and are thus used for the for the second (or reproductive) phase of the growth, or they are used by those people who only wish to purchase 1 single lamp. [5] If high pressure sodium lamps are used for the vegetative phase, plants will usually grow slightly more quickly, but will also have longer internodes, and may be taller. [6]

Recent advancements in LEDs have allowed for the production of relatively cheap, bright and long lasting grow lights that emit only the colors of light required for plant growth. These lights are attractive to indoor-growers since they do not consume as much power, do not require ballasts, and produce a fraction of the heat of HID lamps. The lamps consist of arrays of many wide-spectrum red and a few narrow-spectrum blue LEDs of specific wavelengths. Although LED grow lights have shown promise through plant research by NASA and many universities, it is unknown whether the results are applicable to Cannabis cultivation, as their luminous efficiency is much lower.


LED panel light source used in an experiment on plant growth by NASA. Pictured plant is a potato plant.According to the inverse square law, the intensity of light radiating from a point source (in this case a bulb) is inversely proportional to the square of the distance from the source. So if an object is twice as far away, it receives only 1/4 the light. This is a serious hurdle for indoor marijuana growers, and many techniques are employed to use light as efficiently as possible.

Reflectors are often used in the lamps to maximize light efficiency. Plants or lights are moved as close together as possible so that they receive equal lighting and that all light coming from the lamps wind up on the plants (rather than partly besides it). Often, the distance between lamp and plant is in the range of 24 inches (with incandescent lamps), up to 4 inches (with other lamps as compact, large and high-output fluorescent lamps)[7]. Some marijuana cultivators cover the walls of their grow-room with some type of reflective material, or alternatively, white paint to maximise efficiency.

The most commonly used covering is 6 millimeter (150 µm) PVC plastic sheeting that is white on one side and black on the other. The plastic is installed with the white side facing in to the room to reflect light, and the black facing the wall, to reduce fungus and mold growth. Another common covering is flat white paint, with a high titanium dioxide content to maximize reflectivity. Mylar sheeting is also sometimes used, along with Astrofoil (which also reflects heat), and Foylon (a foil-laminated, reinforced fabric).


grow lights Arranging the right atmosphere
When growing indoors, the cultivator should maintain as close to an ideal atmosphere inside the grow-room as possible. The air temperature must be maintained within an ideal range, typically with deviations no larger than 15 deg.F. with a cooler night and warmer day, and if adequate levels of CO2 are maintained in order for the plants will grow most efficiently. It is also important to promote vigorous air circulation within the grow room, which is usually accomplished by mounting one or more oscillating fans in the room, depending on its size. Using an air extraction fan, sometimes with a smaller fan, ensures air exchange.

Assuming adequate light and nutrients are available to plants, the limiting factor in plant growth is the level of carbon dioxide (CO2). Plants grown with supplemental carbon dioxide will grow more quickly, have larger stomata, and can utilize more light. Ways of increasing carbon dioxide levels in the grow-room include: bottled carbon dioxide, carbon dioxide generators, a milk jug and yeast solution (in which yeast grows in a container hereby emitting CO2), a baking soda and vinegar mixture in a container, or dry ice.[8]

Certain plants (eg most strains of cannabis]] emit a distinctive odor during their reproductive phase. This presents difficulties to those who are cultivating in places where it is illegal. The most common way of eliminating odor is by pulling odorous air through a carbon filter. Many cultivators simply attach a large carbon filter to their air extraction system, thereby filtering any smell before the air is expelled from the grow-room. Another way of eliminating odor is by installing an ozone generator in the extraction ducting. The air is forced past the ozone generator by the extraction fan, and the odorous air is neutralized as it mixes with the ozone; however the cultivator must ensure that the air is thoroughly mixed before it is expelled outside, lest some odor escape. Care must be taken to prevent excessive ozone concentrations in the garden itself, or where it might be inhaled by the grower or his/her family. Ozone itself has a distinctive smell and is harmful to living things, although the molecule breaks down quickly (20 minutes to an hour) in atmospheric conditions.


grow lights Phases of growth

grow lights Germination
Seeds may be germinated by soaking in paper towels, or a cup of water at room temperature, or in wet Jiffy pellets. Regardless of which method used distilled water is always employed as it has the proper pH. Jiffy pellets are often used as a growth medium as they make it unnecessary to transplanting the fragile seedlings. This, as the saturated pellets with their seedlings can be planted directly in the intended growing medium with a minimum of trouble and effort.

When germinating, the seeds must be kept in a dark, moist and warm environment. Germination occurs once water has soaked into the seed and initiates metabolic processes. The seed soon splits and the embryonic root emerges and begins growing downwards due to gravity. Once anchored the root will push the entire seed out above the soil where the seed shell will be lost to expose two circular embryonic leaves (or cotyledons).

This marks the beginning of the seedling stage.


grow lights Seedling phase
The seedling stage of growth begins when the seed breaks the soil and exposes its round “seed leafs” or cotyledon. This is the most fragile time during the entire life cycle of the cannabis plant. It is important to keep a constant atmosphere with a high humidity level and medium to high light intensity. Most growers use compact fluorescents or T5 fluorescents during this stage as they give off little heat. HPS and MH lights give off large amounts of radiant heat and increase the rate of transpiration in the plant. Seedlings have small root systems and can dry out very quickly, thus keeping soil moist is important at this stage. During the seedling stage fertilizers are not necessary and should not be given to the plant. The plant often sexes during this stage but will not preflower.


grow lights Vegetative phase
When the plant possesses 4 sets of true leafs and the 5th is barely visible in the center of the growth tip, the plant has entered the vegetative phase of growth. During the vegetative phase of growth, the plant directs its energy resources primarily to the growth of leaves, stems, and roots. A strong root system is imperative, as it is required for strong floral development. A plant needs 1 or 2 months to mature before blooming. The plant is ready when it has revealed its sex. The males are then culled when they are identified, because they don't produce buds or flowers. If males are allowed to pollinate the females their potency will be greatly reduced, as energy that would have been used to make large, potent buds instead goes to making seeds.

During the vegetative phase of growth, cultivators generally employ an 18 to 24 hour photoperiod, as the plants grow more quickly if they receive more light, although a warmer and cooler period are required for optimal health. While no dark period is required, there is debate among cultivators as to whether a dark period is beneficial, and many continue to employ a dark period.

Marijuana cultivators employ fertilizers high in nitrogen and potassium during this stage, as well as a complete micronutrient fertilizer. The strength of the fertilizer is gradually increased as the plants grow and become more hardy.

The modification of a plant's growth habit is called training. Indoor cultivators employ many training techniques in order to encourage shorter plants and more dense canopy growth. For example, unless the crop is too large to be extensively pruned, cultivators will remove adventitious growth shoots, often called suckers, that are near the bottom of the plant and/or receive little light and will produce poor quality buds.

Many cultivators also employ other techniques:


grow lights Topping
is done by removing the top of the apical meristem (dominant central stem), called the apex or terminal bud, in order to transfer apical dominance (the tendency for the apex to grow more rapidly than the rest of the plant) to the shoots emanating from the two nodes immediately beneath the pruning cut. This process can be repeated on one or both of the two new meristems, when they become apically dominant, with the same results. This process can actually be repeated almost infinitely, but over-diffusion of apical dominance will produce smaller, lower quality buds, so it is usually done no more than a few times. Topping also causes more rapid growth of all of the branches below the cut while the plant heals.


grow lights Pinching
is similar to topping in that it causes the lower branches to grow more rapidly, but the apical meristem will maintain apical dominance, which is especially useful if the plant has already been topped. Pinching is performed by firmly pinching the apical meristem(s) so as to substantially damage vascular and structural cells but without totally breaking the stem. This will cause the lower limbs to grow more rapidly while the pinched tissue heals, after which time the stem will resume apical dominance.


grow lights LSTing
LST stands for Low Stress Training. This technique involves bending and tying the plants branches to manipulate the plant into a more preferred growth shape. This method of training works very well for indoor growers who need to illuminate their plants using overhead lights. Since light intensity greatly diminishes with increased distance (Inverse-square law) LSTing can be used to keep all growth tips (meristem) at the same distance from the light and can achieve optimal light exposure. LSTing is often used in conjunction with topping, since topping increases axial growth (side shoots), topping is often done a few weeks before beginning LSTing. LSTing works by changing the distribution of hormones, more specifically Auxins, in the plant.


grow lights Reproductive/Flowering phase
Plants as cannabis are induced into flowering by decreasing its photoperiod to at least 10 hours of darkness per day. Traditionally most growers change their plants lighting cycle to 12 hours on and 12 hours off. This change in photoperiod mimics the plant's natural outdoor cycle; with up to 18 hours of light per day in the summer and down to less than 12 hours of light come fall and winter. [9]

While the flowering hormone in the most plants (including cannabis) is present during all phases of growth, it is inhibited by exposure to light. To induce flowering, the plant must be subject to at least 8 hours of darkness per day; this number is very strain-specific and most growers flower with 12 hours of darkness to be safe. The flowering hormone is very quickly inhibited, taking less than two minutes of exposure.

Flowering generally lasts from 45 to 90 days indoors. If growing outdoors it may take somewhat longer, depending on the natural onset of the colder seasons. The flowering length is mainly genetically determined with some pure Indica strains flowering in as low as 45 days, while sativa strains can take up to 4 months to finish and the harvest yields significantly less. This is the main reason Indica strains are usually grown indoors.

Some plants, specifically members of the subspecies Ruderalis, will begin the flowering cycle without a significant reduction in their photoperiod; this is called autoflowering, and it is because these strains originate near the equator which does not have the threshold darkness levels in fall.

Flowers from certain plants (eg cannabis) are called Calyx, and are with cannabis the most prized part of the plant. In late flowering the calyx are easily visible to the naked eye. Calyx development begins approximately 1-2 weeks after the photoperiod is reduced. In the first weeks of flowering a plant usually doubles in size and can triple. Calyx development ends around 5 weeks into flowering and is proceeded by a period of Calyx “swelling”. During this time the buds greatly increase in weight and size.


grow lights Increasing popularity
Indoor growing has become increasingly common over the past decade, in part due to increased availability of equipment, seeds and instructions on how to cultivate. So-called grow-ops (growing operations, often located in grow houses) are seen by many marijuana enthusiasts as a much cheaper way in which to gain a steady, higher-quality supply of cannabis. On a larger scale they have proven a viable commercial venture, with some law enforcement agencies finding grow-ops large enough to yield several kilograms of marijuana. More expansive grow-ops, however, are generally more susceptible to detection than smaller operations.

Since individual grow light power generally ranges from 250 watts to in excess of 1000 watts and remain lit for a long time each day, differences in utility bill costs are a significant security issue. It is not uncommon for power companies to work with law enforcement if they witness significant increases in power usage relative to a household's previous electricity costs. Employing energy saving methods is a common way to alleviate this, for instance; switching off light bulbs when leaving rooms, purchasing energy efficient appliances, using TVs or computers less, buying lower power light bulbs and so forth.

Some strains, especially cultivars of Cannabis sativa subsp. indica, can give off strong odors as they grow, resulting in detection. Growers frequently use carbon scrubbers in conjunction with ventilation in order to control odors. This typically involves forcing air from the grow room through a device containing activated carbon, before being vented outdoors. Others use an ozone generator. Ozone reacts with odor molecules in the air, permanently eliminating them. However, ozone can build up to levels that may be hazardous both for the grower and the plant. As a last resort, strong air fresheners are used to control smells as well as keeping windows firmly shut. This is a risky method, as the smell of air fresheners may often arouse suspicion by police officers. Checking outside to see if any smells are emanating from indoors is often a necessary precaution, as many growers become acclimated to the smell, and fail to realize just how pervasive the odor may be. Many store plants in more isolated areas such as a basement or attic to prevent smell detection. Another less common solution is to simply grow a strain which possesses a weaker odor.

Storing plants[1] and lights away from windows and areas which may be seen by visitors is also a common practice, as is keeping the entire grow op in an attic or basement. Some growers, finding this impractical, may cover their windows with light-resistant materials. This can solve the problem of escaping bright light but may arouse suspicion amongst neighbours and local residents.

Many cultivators face detection by fire. Fires normally originate from faulty electrical equipment or wiring. Shoddy fixtures and sockets, improperly grounded equipment, and faulty circuit breakers are some of the most prevalent causes. Due to the large amount of electricity needed for large-scale cultivation, old or damaged wiring is prone to melt and short. Some commercial growers resort to power theft in order to hide electricity usage and many do not take precautions to ensure that their connections are safe. Many growers adapt light cycles so that the lights are on when they are home and off when they are away.

Another fire hazard is plants making contact with hot HID bulbs. Growers using fluorescent bulbs with reasonable air circulation do not have this problem.

Word of mouth can of course be as much a threat to growers as any of the above issues. Often, a few sentences of conversation overheard can result in a tip-off and thus speedy detection. It is for this reason many growers are reticent about their cultivation.

 

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