ABCs of Growing Indoors

Marijuana Grow Basics by Jorge Cervantes


Cannabis (aka marijuana or marihuana) seeds are easy to purchase via mail order. You can buy them from seed companies that advertise in magazines like High Times, Cannabis Culture, Soft Secrets, Weed World, etc. Or you can find them on the internet from sites like Kind Green Seeds. Sometimes you will find seeds in buds.


Clones are branch tips cut from female marijuana plants and rooted. Clones are desirable because they are female and will flower sooner than seeds. A crop of clones can be harvested in about three months. Clones are not available by mail order. You must get them from a grower, or a medical marijuana collective.

A Space to Grow

A grow space is easy to find in any home or structure. The grow space should be enclosed so that you can control the environment inside where plants will grow. You can close off a corner of the basement, the attic, or a room on the main floor to make a grow room. Use plastic, wood or brick to enclose the room. You can also convert a closet into a grow room, or you can purchase a prefabricated grow cabinet or closet.

Temperature Control

The temperature and humidity in grow space will need too be controlled. The ideal temperature for cannabis growth is about 75F (24C). The ideal humidity for cannabis growth is 50-70 percent for pre-flowering and 50 percent for flowering plants. Chances are the environment will need to be heated or cooled a little to maintain the ideal temperature and humidity. Often a ventilation fan is all you need to keep the temperature and humidity perfect.

Air Circulation

Marijuana uses carbon dioxide (CO2) from the air. The CO2 is used up quickly around foliage, and the air must be circulated so that new CO2 comes in contact with leaves. You will need an oscillating circulation fan to keep the air stirred up and CO2 readily available for plant intake. A circulation fan will als mix the hot air on top and cool air below so the temperature is even throughout the room.

Air Ventilation

Marijuana uses all the available CO2 in a room pretty fast. A ventilation fan expels used CO2-poor air. The vent fan also removes hot, humid air from the grow space. Fresh, cool, dry air rich in CO2 is drawn into the room via a fresh-air intake vent.


Provide light with fluorescent tubes, compact fluorescent lamps (CFLs), metal halide lamps, or high pressure (HP) sodium lamps. Each lamp has positive points and limiting points. Fluorescent lamps are best suited to growing seedlings and clones. Inexpensive CFLs can grow small crops from start to finish. The best CFLs for growing are available in wattages from 65-125. More expensive and versatile metal halide and HP sodium high intensity discharge (HID) lamps are available in many wattages (from 150 – 1500) and color spectrums. Both can be used to grow crops from beginning to end.

Water and Drainage

Ordinary tap water is usually adequate to grow cannabis. If it is okay to drink, it is usually okay for your plants. If your water tastes bad and is full of sodium and other minerals, you may need to treat it with a reverse osmosis filter. Such control is usually not necessary when growing with soil.


Hydroponics means growing in a soilless mix that serves to anchor plant roots. Hydroponics allows the grower to control fertilizer (nutrient) levels and uptake by plants. Hydroponic grow mediums provide more air space around roots, and nutrient uptake is faster than in soil gardens. Hydroponic gardens require more control of water, pH, nutrients, and the root-zone environment. Hydroponic gardens can be very simple and inexpensive or complex and expensive.


Growing in soil is simple and easy. Always purchase good soil that drains well. If you cannot find good soil, mix your own from quality components. Organic soil gardens beast the best flavor and fragrance.

Cannabis Life Cycle and Indoor Growing

Cannabis cultivated indoors needs light, air, a growing medium, warmth, nutrients, and water. As explained earlier in this chapter, you can control all these needs in yur indoor garden and achieve optimum results.

Cannabis is a shirt-day plant. In nature, it flowers when autumn days are short and nights are long. Outdoors, cannabis normally grows as an annual plant, completing its life cycle within one year. A seed that is planted in the spring will grow through the summer and flower in the fall, producing more seeds.

Cannabis goes thru three distinct stages of growth: seedling, vegetative, and flowering. Most varieties or strains will stay in the vegetative growth stage as long as they receive 18-24 hours of light and 6-0 hours of darkness. Most strains of cannabis will flower when they receive 12 hours of light and 12 hours of uninterrupted darkness.

Indoors you can use this knowledge t control the life cycle and harvest up to six crops a year.

Seedling Growth

Seed germination is induced with moisture, heat, and air which activate hormones within the seed. Within 24-72 hours the seed’s coating splits and a white rootlet emerges and continues t grow.

After three to seven days of germination, the rootlet grows downward and a sprout with seed leaves pushes upwards in search of light. During this stage the seed establishes a root system and grows a stem with a few leaves. Seedlings need 16-18 hours of light to grow strong and healthy.

Vegetative Growth

Vegetative growth is maintained by giving plants 18-24 hours of light every day. As the plant matures, the roots take on specialized functions of transporting and storing food. The root tips push farther and farther int the soil in search of more water and food. The delicate root hairs actually absorb water and nutrients. Delicate root hairs will dry up and die without water. They are very frail and are easily damaged by light, air, and bumbling hands if moved or exposed. The stem also grows upward producing new buds along the stem. The central or terminal bud carries growth upward; side or lateral buds turn int branches or leaves. The stem carries water and nutrients from the roots to the growing buds, leaves, and flowers. If the stem is bound too tightly by string or other tie-downs, it will cut the flow of life-giving fluids, thereby strangling the plant. The stem also supports the plant.

Often indoor plants develop weak stems and may need to be staked up, especially during flowering. Bending and training plants also makes best use of light indoors.

Chlorophyll (the substance that gives plants their green color) converts carbon dioxide (CO2) from air, water, and light energy int carbohydrates and oxygen. This process is called photosynthesis. Tiny breathing pores called stomata are located on the underside of the leaf and funnel CO2 int contact with the water. The stomata open and close to regulate to flow f moisture, preventing dehydration. The stomata also permit the outflow of water vapor and waste oxygen.


Cannabis grown from seed grows pre-flowers after the fourth week of vegetative growth. They generally appear between the fourth and sixths node from the bottom f the plant. Cannabis plants are normally either all male or all female. However, occasionally an intersex plant with both male and female flowers will appear. Each sex has its own distinct flowers. Pre-flowers will be either male or female. Growers remove and destroy the males (or use them for breeding stock) because they have low levels of cannabinoids (chemical components of marijuana: THC, CBD, CBN, etc.). the most desirable female plants are cultivated for their high THC content.


Flowering is triggered in most strains f cannabis by 12 hours of darkness and 12 hours of light every 24 hours. Once flowering is induced with the 12/12 light/dark schedule, they are at peak ripenesss in 7-12 weeks. Plants that develop in tropical regions often start flowering under more light and less darkness.

Flowering Male Plants

Male seedlings that were not removed during pre-flowering are removed as soon as male flowers are visible so that they do not pollinate females.

Flowering Female “Sinsemilla” Plants

Unpollinated female flower buds develop without seeds, known as “sinsemilla”. Sinsemilla flower buds continue to swell and produce more resin while waiting for male pollen to successfully complete their life cycle. After weeks of heavy flower and cannabinoid-laden resin production, THC production peaks out and buds are ready to harvest.

Seed Crops

When both male and female flowers are in bloom, pollen from the male flower lands on the female flower, thus fertilizing it. The male dies after producing and shedding all his pollen. Seeds form and grow within the female flowers. You can collect the seeds roughly six to eight weeks after pollination.

Mother Plants

Select strong, healthy, potent mother plant. Give mothers 18-24 hours of light daily so they stay in the vegetative growth stage. Cut branch tips from mother plants and root them. The rooted cuttings are called “clones”. Cultivating several strong, healthy mother plants is the key to having a consistent supply of all-female clones.


Cut branch tips and root them to form clones. Clones take 10-20 days to grow a strong healthy root system. Give clones 18-24-hours of light so they stay in the vegetative growth stage. Once the root system is established, transplant clones into larger containers. Now they are ready to grow for one to four weeks in the vegetative growth stage before being induced to flower.

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