Indoor Marijuana Grow Room with Plants in Soil Under Lights

Growing Cannabis:  The Basics

For all the talk about marijuana as a part of American culture and lifestyle, a lot of people tend to forget that cannabis is a crop. And like any agricultural product marijuana requires a lot of maintenance and care if a grower hopes to harvest a plentiful and potent group of plants.

Getting Started

Cannabis plants are either germinated from seeds or grown from “clones,”  that is, cuttings from a “mother” female cannabis plant. There are both advantages and disadvantages to using seeds and clones. You’ll need to determine which works best for your operation, although a growing numbers of growers use clones.  You’ll also have to decide on the best grow medium for your plants, as well as lighting and water systems.

The Cannabis Grow Cycle

It takes around 90 days, from sprout to maturity, to get an average cannabis plant fully grown and ready for harvest.

Once your seeds have germinated or your clones have been established, the plants begin what is known as the Vegetative Stage.  The sprouts do most of their growing in this stage. In indoor operations, experts recommend that cannabis plants be grown in a warm and relatively humid environment (around 75 degrees Fahrenheit and 40 percent humidity) with good air circulation, and exposed to light from 18 to 24 hours a day.

Depending on the cannabis strain, the Vegetative Stage can last anywhere from one to two months.

The next phase of growth is the Flowering Stage. This is when the plant will create its potent buds and grow to its optimal size. The plant will require 12 hours of full darkness and 12 hours of light to initiate the flowering process and force bud production.  The Flowering Stage can last from 8 to 10 weeks.

Once the cannabis buds are ready, they’re then harvested and cured, or dried slowly in a controlled environment.

Energy Costs

More than 90 percent of cannabis grown in the United States is currently grown indoors.  A recent study prepared for San Diego Gas & Electric found that the cost of electricity in indoor “grows” makes up between 20 and 50 percent of a grower’s operational expenses.  Grow lights are the largest electrical consumers, followed by HVAC and other climate control equipment.

Many states where marijuana is legal are working to reduce carbon emissions from their cannabis businesses and elsewhere, which is encouraging cannabis grow operations to invest in cost-efficient LED lighting as well as solar and even wind power.

Water usage

Cannabis requires a lot of water, around two gallons a day per plant.  Researchers quoted by the Press-Democrat in Sonoma County, however, estimated that mature pot plants grown at a group of northern California greenhouses were consuming six gallons of water daily per plant, which might be the extreme end of the scale. At any rate, if you factor in evaporation rates and waste, that’s a lot of water.  Some cannabis growers also use hydroponic systems, which cultivate marijuana in a soil-less medium where the plant’s roots are suspended in water containing nutrient-rich H2O.  But many growers are developing their own sustainable watering systems, which terrace plants and ensure very minimal water waste.


Cannabis plants, even those grown indoors, are vulnerable to a variety of insect pests.  States with legalized marijuana programs have very specific regulations regarding the types of pesticides that can be used on cannabis, as well as the dosage of those chemicals. Violation of these pesticide regulations can lead to entire crops of cannabis being seized or even destroyed. Some growers avoid pesticides and try to use organic pest control, such as lady bugs and other insects that prey on cannabis-eating pests.


For more detailed information about cannabis growing, consult the following:

Cannabis 101 –

Growing Weed for Dummies: 10 Simple Steps to Get You Started – Green Rush Daily

Pesticide Use in Cannabis Production Information – Colorado Department of Agriculture