Where you grow your marijuana plants is important, whether you choose inside or outside. You should make sure you choose a good spot that is not frequently used, such as your basement, an attic or a small closet. The growing location will need electrical outlets inside or nearby. You should plan for any repairs to be done prior to starting your grow room so that no one stumbles across your secret. Once you have chosen a growing location, it then becomes time to prepare. We are going to assume that a closet was the location of choice for the purposes of this guide. First you will need flat white paint covering all of the walls You do not want to use aluminum foil as that can reflect light poorly, damaging the leaves. Next you will need to cover the entire closet floor with plastic so that you do not wind up with water damage on the floors.
You will need a container of some sort to grow your marijuana plants. Most people use plastic pots. The bigger the pot, the larger your final plant will be. Cover the bottom inch (2.5 cm) of the pot with gravel to increase drainage. Follow that up with good-quality top or potting soil with a mixture of sand. If you decide to use buckets, make sure you drill drainage holes in it first. Make sure each pot you use is totally sterile before starting this process. We recommend using alcohol or bleach, rinsing it clean when done.
You will need lights to mimic sunlight to your marijuana plants. You can choose fluorescent bulbs, which are cheaper, cooler and efficient, metal halide (MH) bulbs which are a bit more expensive but much brighter on your plants, or High-Pressure Sodium (HPS) bulbs which are equally as bright as MH bulbs but not quite as warm. Both the MH and HPS bulbs require you to buy a ballast in order to use them. You will also need a good source of ventilation.
If you want cheap lights, then go with fluorescent lights. There is little heat coming off of them so you may not need to vent the space, unless it is tiny. The spectrum of lights that are given off will work during all growth phases for marijuana plants. Due to how large of an area that is covered by these bulbs, you will need to keep them within 2-4" (5-10 cm) of your marijuana plants so that each plant gets enough light. What this boils down to is mounting your lights so they are mobile, allowing for constant readjustment.
If you want a lot of light, you will want to go with metal halide (MH) lights. The problem is, they also make the room very hot. You will need proper ventilation if using these lights. There is a lot of blue spectrum lights coming from these bulbs, so they are ideal during vegetative growth. They can also be used when your marijuana plants are flowering if you want to have only one set of lights. You will need to buy a ballast to use these bulbs. You can get these bulbs in anything from a 40 watt size to a 1,000 watt size. If you buy a 1,000 watt size bulb, it will work for a closet with four good size marijuana plants.
If you want a good source of light but with lower amounts of heat, you want a high-pressure sodium (HPS) bulb. You will still need ventilation but the temperature will not be as difficult to control. You will get more of the orange and red spectrum of light, which works well with flowering marijuana plants. You can use these bulbs during vegetation growth but the leaves will come out a bit slower. You will also need a ballast with this setup. Many marijuana growers use this in combination with the MH bulbs so they have the right light spectrum during each phase of growth. You can even start your seedlings with fluorescent bulbs, then go to MH bulbs for vegetation and HPS for flowering. Fluorescent bulbs will stress out the plants the least due to how weak they are. You will ultimately have to choose what is best for your growing location, no matter if it is a closet or an attic.
You will notice changes in photosynthesis with more than just the differences in amounts of light. Growers have learned how to change these factors to increase growth rates and yields.
The quantity of water vapor your growing location has in the air represents the humidity. You will want to stay below 85% to avoid bud mold. You will also want to make sure to watch your humidity closely during the most fragile stages of seedling development. You will want to try and stay above 80% to keep the medium moist for germination to occur. If you want to increase the growth rate of your marijuana plants, try and keep the humidity between 65% and 80%. If you go under this amount, your plants will be thin and fragile, and if you go over this amount, your plants will not be able to remove chemicals through the evaporation process.
Even though marijuana plants have the capabilities of survival in anything from 32 °F to 100 °F (0 °C to 38 °C), your marijuana plants will have the best growth rates between 70 °F and 75 °F (21 °C and 23 °C). Temperatures that are too high or too low will affect photosynthesis and cause a breakdown of the plants.
The gas that is considered essential for every light reaction within plants that go through photosynthesis is carbon dioxide (CO²). The stomata of the leave absorbs CO² and then mixes with light energy and water to produce glucose and oxygen. Glucose is used by plants as energy, and the oxygen is released into the air. This means that if you increase the CO² around your plants, photosynthesis will speed up and your marijuana plants will grow faster. Growers have also found that if you supplement your marijuana plants with CO², they can live in higher temperatures without a decrease in photosynthesis.
You never want your marijuana plants to dry out because a lack of water will slow down photosynthesis. When your marijuana plants do not have enough water, the plants will close their stomatas, keeping the toxic chemicals within the plant. This can either significantly slow down photosynthesis or it can stop the process entirely.
A sea of green (SOG) is when growers harvest a bunch of tiny plants on a frequent basis instead of growing a lot of bigger plants that they harvest less often. The setup for SOG is typically within a closet that has two separate lit areas. The upper portion has a timer giving your marijuana plants 12 hours of light and 12 hours of dark, while the lower portion has a timer set to give your marijuana seedlings 18-24 hours of light. Fluorescent bulbs are the lights of choice for this setup because it is safe for all phases of growth. The upper portion is used when the plants are flowering while the bottom portion is used for germination or cloning seedlings. This allows for monthly harvesting.
All plants remove waste through the stomata on their leaves, and marijuana plants are no different. When plants are grown outside, the weather helps the evaporation process with the sun, rain and wind. However, when plants are grown inside, it is up to the grower to mirror this process to allow the plants to detoxify. A fan is usually sufficient for this process. If your growing location is large enough, you can get a fan and leave it on. If you are using a small growing location, you may not need a fan. Some small locations only need the change of air that opening the door to the location can create. A timed fan that goes on and off can also work. If you happen to have a large crop, you may also need a dehumidifier to keep the humidity below mold-growth levels.
Occasionally, growers will add CO² into the growing location to help increase the growth rates of their marijuana plants. This will also allow your marijuana plants to continue growing at a high rate of speed even if they are in temperatures of up to 95 °F (35 °C). Some growers have noticed a decrease in potency when CO² is supplemented during flowering, so we would recommend you stop this process when you flip the lights to 12 hours of light and 12 hours of dark.
Due to how easy it is to control how the lights cycle around your indoor marijuana plants, you should have no trouble determining sex. Flip your light cycle to 12 hours of light and 12 hours of dark once your marijuana plants hit 8" (20 m) high. Examine the flowers with a magnifying glass and remove all of the male plants before they are able to pollinate the females.
It may be a good idea to allow a couple of females to be pollinated because then you will get seeds for future crops. This can be done with a few plants and will allow you to still have a good harvest with the rest of the females. All you have to do is gather some pollen from the best males (those that grow quickly, do not get sick and have a potent smoke to them) by shaking some of the branches over a plastic bag or sheet of dark paper. If you need to store the pollen until you can use it, we recommend old film containers. Then you take a paint brush and brush the pollen on to the females lowest branches. We recommend you do not harvest those branches you pollinated because then you are assured you will get a viable crop of marijuana seeds.
Once you are ready to have your marijuana plants go to flower, you simply need to flip your light cycle to 12 hours of light and 12 hours of darkness. This part is difficult for some people because the only thing you can really do during this time is be patient, allowing for the flowers to bud and mature. If you can avoid watering in the last week prior to harvesting, it can help the drying procedure slightly. Get rid of the largest of the fan-style leaves and compost them for good soil for your next batch. Take the portions of the marijuana plant that can be smoked and put them into either paper bags or shoe boxes, then you stir them around each day. After approximately three weeks, your harvested buds should be completely dry, leaving you with a product that is ready to smoke.
Want to read more about marijuana? Go to our marijuana grow guide.