To successfully cultivate cannabis, indoor and outdoor alike, it’s important to understand the fundamental requirements plants have in order to produce food and prosper. Essential to cannabis or any plant is:
- a growing medium
- proper temperature
In this post we will mainly focus on indoor growing, as our goal is to describe how-to setup an indoor grow room on a budget. For Part I we’ll discuss light and growing mediums. With that in mind, let’s take a look at what the plant needs to be able to survive while simultaneously looking at inexpensive options that efficiently meet those needs.
Remember- cannabis will grow as fast as its most limiting factor; when cultivating indoors the most variable factor, and thus typically the most limiting factor, is light.
Plants use only certain portions of the light spectrum. The most important colors for maximum chlorophyll production and photosynthetic responses fall within the blue and red ranges. The main chunk of light used by plants lies between 400 and 700 nanometers (nm), this region is termed the Photosynthetically Active Radiation (PAR) zone. “PAR watts” is the measure of specific photons a plant needs to grow. Each color of light activates different plant functions.
Your plants’ needs can most definitely be met by common household incandescent light bulbs. But (oh come on you had to see but coming otherwise everyone’s tent would be filled with them!) these particular bulbs emit an extremely high percentage of both far red and infra-red light. It’s a good thing to remember that red light usually encourages stem growth while blue light is used for foliage growth. So what am I saying here? Common household incandescent bulbs would cause the plants to focus its growth more on the stem (rather than directing its energy toward foliage growth) resulting in stretched and extremely tall plants. We don’t really want that now do we? Hence these types of bulbs tend to be avoided altogether. A cheaper and efficient alternative that does get the job done is compact fluorescent light (CFL) bulbs, but these will be covered in more detail shortly.
Ultimately the grow room’s size determines both the size and number of lamps required to cover the floor space available for your particular set-up. High intensity discharge (HID) lamps work well to cultivate medicinal marijuana and are available in wattages of 150, 175, 250, 400, 600, 1000, and 1100. While the lower ranges (150-400-watts) work better for closet spaces or areas with 9-21 square feet of floor space, high watt bulbs (600 watts +) work best for larger areas.
The two most popular types of HID lamps used in cannabis cultivation are metal halide (MH) and high pressure sodium (HPS). Let’s dig a little deeper into each one:
Metal Halide (MH)
Metal halide HID bulbs are typically used during veg stage. They come in 175, 250, 400, 600, 1000, 1100, and 1500-wattage sizes. They may either be clear or phosphor coated and requires special grow light ballasts. Light Ballasts convert electricity from standard outlets into the voltage needed to operate high intensity lighting. As mentioned earlier, the smaller 175 or 250-watt bulbs better suit smaller closet grows. The 400, 600, 1000, and 1100-watt clear halide bulbs are the most popular amongst indoor growers as they supply bright lumens that stimulate plant growth.
Note: the 1500-watt halide tend to be avoided altogether because it has a relatively short 2,000 to 3,000 hour life span and incredibly high heat output, making it both cost ineffective and potentially dangerous.
High Pressure Sodium (HPS)
High pressure sodium HID bulbs (which also require special ballasts) are available in 35, 50, 70, 100, 150, 200, 250, 310, 400, 600, and 1000-watts. They emit an orange-tinged glow that is said to resemble the hues of harvest sun. Due to the color spectrum of HPS bulbs being highest in the yellow, orange, and red ranges, the light from the red end of the spectrum stimulates floral hormones which promote flower production in the plant. This is why HPS bulbs are utilized during flower stages.
Each watt of HPS light input yields between 3/8 – 1gram of bud.
Compact Fluorescent Light (CFL)
Remember I brought CFLs up earlier as a cheaper yet still efficient alternative? While CFLs are not as bright as HIDs they do cover the full visible light spectrum. This makes them great for growing medical cannabis and they continue to be popular in small-scale closet and tent grows. Why so may you ask? They generate little heat, in turn requiring minimal ventilation, and are perfect for growers working with a limited budget and a smaller grow space. CFLs provide enough light to grow medicinal marijuana from seed to harvest. Common sizes used for growing medical marijuana include 55, 60, 65, 85, 95, 120, 125, 150 and 200-watts. So which CFL bulbs fit veg and flower best? Bulbs between 5,000-6,500 Kelvin offer plenty of blue light that promotes plant growth during veg. Ranges from 2,700-3,000 Kelvin offer higher yellow and red spectrums that are better utilized during flower.
Now here is the kicker– prices for these bulbs at your local Home-Depot store are:
5,000 Kelvin (veg)— $2.29/bulb
2,700 Kelvin (flower)— $2.19/bulb
Just a couple of bucks per bulb!
Although CFLs are the most inexpensive route, they still fall short in efficiency when compared to MH and HPS HID bulbs.
CFLs emit approx. 25-35% less light/watts than HPS bulbs.
T-5 fluorescents emit approx. 25% less light/watts than HPS bulbs.
T-8 fluorescents emit approx. 30% less light/watts than HPS bulbs.
My personal choice based on reading many articles, comments, and books leans towards using MH HID bulbs both during veg and flower. Paraphrasing what “The Rev” (an organic cannabis cultivator and writer for a popular magazine) once said, he claimed that the fruits of a cannabis harvest come out more potent and flavorful under MH. In my personal opinion you may lose out on yield, but then again it comes down to what you’re looking to produce. Potent medicine? A flavorful medicinal head stash? An industrial sized crop?
Ultimately no artificial lighting compares to Mother Nature. In full sun you can expect to harvest between 1/3 – 1oz per square foot of canopy. Yikes!
If this is your first grow and you are looking to be as cost-effective as possible, then growing either in soil, soilless, or coco medias is going to be the best choice for you. Building a hydroponic set-up or other advanced systems will run a bit pricey, as you have more initial costs to invest in (for equipment) than traditional methods.
Traditional soil medias may contain compost, perlite, fir bark, peat moss, sand, and many commercial soils may even come with added fertilizers (be careful, as already fertilized soils are considered to be “hot” and adding additional nutrients may lead to nute-burn). High quality commercial potting blends should meet your plants’ requirements if it has the correct texture, water retention and drainage needed for growing medical marijuana. The main advantage of using soil or soilless medias besides being rather inexpensive (especially for smaller grows), is its natural buffering ability in maintaining a constant pH (idea pH levels in soil is between 5.9 and 6.5), as well as being extremely forgiving on first time growers during water-feedings.
Coco media are made from coconut husk fibers, are reusable, and take a longer time to break down. Resembling rich soil in texture, the fibers that make up coco medias provide great aeration, drainage, as well as water retention.
Other soilless mediums can be made up of peat moss, redwood fiber mulch, lava rock, and perlite as an alternative to traditional soil-based growing mediums. If you’re growing indoors, soilless media have the advantage of not encouraging insect infestation.
Check back next week for Part II and we’ll explore Air/CO2, water, and nutrients in your indoor grow room.