Lighting Types


Light is necessary for a plant to transform nutrients into food. It also has a great influence on chlorophyll production, growth rate, leaf size and seed production. Light becomes one of the most important aspects of your planting operation. For the purpose of marijuana planting there are two basic types of light; Fluorescent and High Intensity Discharges (HID) – including Mercury Vapor (MV), Metallic Vapor (MH) and Sodium Vapor (HPS)


The main difference is that fluorescent lamps create light in the passage of electricity through a low pressure gas vapor and HID create light in the passage of electricity through a high pressure gas vapor. HID are MUCH brighter and although they represent a higher cost in the beginning, they are more cost-effective and allow for better production. Therefore, they are the first choice for most indoor breeders.


Fluorescents are found in the most varied shapes and sizes. There are compact bulbs, twisted bulbs and circular bulbs. They all work the same way. They have a built-in starter and ballast allowing regular and safe electricity delivery to the light. Before HIDs were available for planting indoors, planters used fluorescent lamps, which despite working during all stages of cultivation, are not advisable for use in this way. For effective planting with fluorescents, think small. These are bulbs suitable for germination, root production in clones and small plants, maintain mother plants for cloning purposes and also provide side lighting for the growth of the lower branches. These situations do not require high intensity light to develop. The light emitted by the fluorescent lamps is soft and more diffuse, does not give off a large amount of heat and does not make the plant work as hard. For this reason it can be left close to the plant. Three to five centimeters is enough, but due to this the lights should be adjusted almost daily, which can be problematic.


There are basically three types of HID. Mercury Steam (MV), Metallic Steam (MH) and Sodium Steam (HPS). These lamps also need a starter and ballast.

Mercury vapor (MV) and the type of light that was used in street lighting in the past. It is not very good for planting because it does not provide the correct light spectrum. While it produces a little bit of the blue spectrum, MV also produces a lot of heat to be close to the plant, being very inefficient to operate.

Metallic Vapor (MH) is a very good source of blue / white light spectrum which is ideal for vegetative growth. Many planters use MH during the vegetative phase. MH is brilliant and cost efficient to operate, but not as efficient as HPS lamps. The most used powers are 400 and 1000 watts. They work best when combined with HPS lamps.

Sodium Vapor (HPS) is the best lamp choice today for planting marijuana. HPS are very bright and very efficient. This type of light has a red / orange spectrum that is ideal for the flowering stage. With enough of that kind of light you can also grow those Hightimes poster “shrimp”. HPS are found in various powers from 70 to 1000 watts.


Your plants should be started in the growing season in a 24/7 or 18/6 light regime. The reason for the 18/6 regime is to leave a dark period for the plants to rest and also to save your electricity bill. Most plants are exhausted after 16 hours of light a day. Adjustments should be made according to the needs of the plants. For flowering 12/12 is the norm. Again, adjustments can be made. A minimum of 12 hours of darkness is required to activate flowering.


Do not burn the plants by placing them too close to the lamps. Fluorescent lamps do not emit much heat and can be about 3 to 5 cm apart. HID emit a lot of heat and need to be within a reasonable distance. A good test is to place the back of your hand between the plant and the lamp for some time, if there is a feeling of discomfort it is because the lamp is too close. There are some common bulbs that can induce germination, but are useless for growth purposes. These lamps are: Any incandescent (normal), halogen, black light and heating. Don’t waste time trying to plant with these bulbs, you just fall off

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