How to Grow Cannabis

Updated: Aug 17


Origin
Strains
Growth
Growing Cannabis from clones
Growing Cannabis from seeds
Growing Cannabis indoors
Growing Cannabis outdoors
Growing Cannabis hydroponically
Fertilizing
Harvesting
Pests
Diseases


Origin


Cannabis is a flowering plant that is grown for its flavonoids, psychoactive cannabinoids (THC) and terpenes that have both physical and psychological effects on the body. There are two main Cannabis types, Cannabis sativa and Cannabis indica. Cannabis sativa is native to Southeast Asia, Central America and South America where the plants grow to be very tall and skinny. Cannabis indica is native to the middle eastern countries of Afghanistan, Pakistan and Tibet. These plants grow to be much shorter and bushier than Cannabis sativa.



Strains


There are thousands of cannabis strains available for purchase with more being developed regularly by crossing different strains to make hybrids. Strains are hybridized by fertilizing a male variety of one strain with a female variety of another strain. Here are some of the most popular hybrid strains available today:


  • Sour Diesel (Sativa)

  • Jack Herer (Sativa)

  • Blue Dream (Sativa)

  • Bruce Banner (Sativa)


  • Hindu Kush (Indica)

  • Girl Scout Cookies (Indica)

  • Northern Lights (Indica)

  • Wedding Cake (Indica)



Growth


Cannabis is a dioecious flowering plant that produces male and female reproductive organs on separate plants. Male plants are undesirable because they do not produce flowers. These plants produce pollen sacs that fertilize the female plant’s flowers. Once the flowers on the female plant have been pollinated, the plant will stop flowering and begin producing seeds. Therefore, male plants should be discarded as soon as their sex has been determined to prevent them from pollinating the female flowers.


To determine if your plant is male or female, look for the reproductive organs. Male plants develop very apparent pollen sacs and female plants produce flower buds. The first sign of a flower bud on a female plant are the stigmas which look like white hairs coming from a bud at the crotch of a stem.

The downfall of not knowing if your seeds have been feminized is that the only way to know the sex of your plants is when they begin to develop their reproductive organs. This can be a time consuming and costly process.


Unlike clones, cannabis grown from seed can vary in their genetics. Each seed carries 50% of the genes from the female plant and 50% of the genes from the male plant.


Cannabis plants stay in their seedling growth phase for about 2-3 weeks until they are able to grow strong enough to produce full leaves. Once the plant has grown at least one set of full grown leaves, it is in its vegetative growth phase until it flowers. The vegetative growth phase is the prime time to get the plant full and healthy before it flowers. This is also the best time to begin pruning so you have a bushier plant with multiple stems to grow flower buds on. The more stems the plant has, the more potential there is for higher flower yields. The pruning process while the plant is in its vegetative growth phase is pretty simple. Cut back each stem while the plant is young to encourage bushier growth. Multiple stems will grow from the cut point opposed to just one, long stem.


Cannabis plants that become stressed can turn into hermaphrodites, developing both male and female sex organs on one plant. These plants should be discarded because the pollen will fertilize the flower buds and cause them to produce seeds instead of large flower buds.



Growing Cannabis from clones


Taking clones is a quick way to start cannabis plants because it eliminates the seed germination and seedling growth stage time frame. Clones are cuttings taken directly from a mother plant and will have the same genetic makeup as that plant. Mother plants are chosen for the desirable traits of specific strains. They are kept in a vegetative growth stage to be able to provide an unlimited supply of clones for continuous crops. The mother plants are able to stay in a vegetative growth stage by keeping light on them 18+ hours a day. Any period of darkness or reduction in the amount of light hours they receive will move them into a flowering stage and they will no longer be able to be used as plant stock.



An added advantage to growing cannabis from clones is that the sex of the plant is known to be female. Unless the seeds you are using are verified to be feminized seeds from a breeder, there is a possibility that some are males. Growing cannabis plants from seed only to find out they are male is a costly attempt.


Tools You Will Need to Grow Clones

Seed Starting Kit with Soil Medium


How to Clone a Cannabis Plant

Step 1: Choose a thick stem with no sign of disease. The stronger the stem and leaf growth, the stronger the clone will be.


Step 2: Make the cut right below any node and about 6” down the stem at a 45° angle. Cutting at an angle allows for more surface space for roots to grow.


Step 3: Trim off the lowest leaves on the cutting, leaving only 1-2 leaf sets at the top. Leaving the bottom leaves on the stem can cause rotting if they rest in water or on moist soil.


Step 4: Dip the tip of the cutting at the node in a rooting hormone such as Clonex.


Step 5: Immediately place the cutting in a soilless planting medium such as perlite, coco coir, rock wool cubes or an aeroponic system. Cuttings not immediately given moisture will quickly wilt and begin to die, degrading the health of the cutting.


Step 6: Regularly mist the leaves to boost moisture.



Growing Cannabis from seed


When growing cannabis from seeds, it is best to germinate more seeds than you intend on keeping. Not all seeds will germinate and some might be males if not feminized from a breeder. Seeds do not need high quality soils to germinate. Any type of soil medium such as peat moss, coco coir or perlite will work as long as you are keeping the medium moist at all times until the seeds germinate. General potting soil can be used, but the high organic matter in potting soils can cause bacteria and fungal growth which can be detrimental to young seedlings if too much moisture builds up.


Seeds should be started indoors in a warm environment. Seeds need temperatures to be at least 60° F to germinate properly. Temperatures below 60° F can cause a fungal disease called ‘damping off’ from an excess amount of soil moisture combined with low temperatures. Signs of damping off are very thin stems that eventually rot and collapse. Warming mats can be used to increase warmth. With proper moisture and warmth, germination can take about 3-10 days.


Auto-flowering Seeds


Auto-flowering seeds are a type of seed that have been bred with genetics causing them to grow rapidly that allow the plant to be grown from seed to harvest in three months. The flowering growth phase on these plants is automatic and not determined by the amount of sunlight they get. These plants are smaller in size and have lower yields, but multiple crops can be grown in a year because of how fast their life cycle is.


Tools You Will Need to Germinate Seeds

How to Grow Cannabis from Seed

Step 1: Fill a germination tray with the soil medium and give it a good soaking so it becomes absorbent.


Step 2: Place the germination tray on a warming mat.


Step 3: Bury the seeds ¼-½” deep and 1” apart or one seed per cell depending on the type of germination tray and cover with the soil medium.


Step 4: Water the soil again to ensure it tightly forms around the seeds.


Step 5: Mist the soil with a spray bottle when the soil begins to dry. Avoid heavy, overhead watering to reduce the chances of disrupting the seeds.


Step 6: As soon as the seeds germinate and there is growth above the soil line, place a grow light over the seedlings for at least 18hrs a day.


Step 7: Pinch off multiple seedlings that have germinated in the same cell leaving only one so they don’t compete with each other for resources. Pinching off the seedlings instead of pulling them out will prevent the disruption of the kept seedlings roots.


Step 8: Transplant the seedlings to larger pots or in the ground when they have at least two sets of leaves.



Growing Cannabis indoors


Growing cannabis indoors is highly beneficial because anyone that lacks outdoor space can do it. Growers have the ability to get more creative with indoor grow space by utilizing a smaller space. Crops can either be grown in soil, hydroponically or aeroponically indoors. A huge benefit of growing cannabis indoors is that crops can be grown any time of year, regardless of the season because all variables such as lighting, temperature, humidity, water and nutrients can be controlled.


Cannabis plants grown indoors should be under at least 18 hours of light a day until they are big and strong enough to bear flowers. More hours of light is needed for indoor plants because artificial lighting is not as strong as natural sunlight. The vegetative growth stage time frame can be anywhere from two to eight weeks and the flowering time frame ten to sixteen weeks depending on the cultivar. Once you want your plants to begin flowering, reduce the lighting to twelve hours a day until harvest. If there is any chance of light interference during the twelve hours of needed dark hours to promote flowering, blackout materials such as grow tents can be utilized.



Since indoor spaces must be manipulated to be healthy growing environments for plants, equipment such as fans and dehumidifiers should be installed. The more plants you grow in an indoor space, the more humid the air will become. If humidity levels are above 50% and there is not enough air flow, fungal spores can accumulate and infect your plants. The air temperature should be between 68° F and 85° F. Temperatures out of this range can put stress on the plants, inhibiting flowering. Humidity levels and temperature can be measured using a hydrometer.


Unless you are growing your plants hydroponically, highly nutritious soil should be used. The soil you use can be premixed or you can make your own recipe as many experienced growers do. Foxfarm company has a large variety of high quality soils and soil conditioners.


Tools Needed:

Benefits
  • Ability to manipulate all growing conditions.

  • Can grow any time of year, regardless of the season.

  • Minimal environmental pollutants.

Drawbacks
  • Can be expensive due to startup costs on equipment and utilities.

  • Bacteria and fungal diseases can easily spread if there is a lack of air flow or the humidity is too high.

  • The plants emit odors, especially when flowering.



Growing Cannabis outdoors


Growing cannabis outdoors is great if you have the space and nutrient rich soil. You will need to ensure that your outdoor space is secure from other people and pollutants. Cannabis plants grown outdoors need at least six hours of sunlight a day for healthy growth.


To get a jump start on the season, seeds can be germinated indoors and transplanted outdoors once the seedlings have developed at least two sets of true leaves.


Plants should be put in the ground by the summer solstice on June 21st when there are the most sunlight hours in a day and the least amount of dark hours. The plants will begin to flower in the fall when the amount of sunlight hours decrease and night time hours increase. Outdoor lighting can be manipulated as done in indoor grows but requires light deprivation material.


When growing outdoors, it is important to test the soil quality, especially if it is not known what the property was used for prior. Soil tests can be sent to local labs to test for various things such as pollutants, nutrients and pH. Contact your local extension office for resources on where to test your soil. If your soil is not nutritious and the structure is clay-like or sandy-like, it must be amended with more nutritious and porous soil before planting. A mixture of the native soil, compost and manure will liven up the soil.


Plants should be spaced at least three feet apart for proper airflow and for more maneuverability between the plants. Install support posts or trellising to ensure your plants do not bend over, especially for sativa cultivars that can grow to be very large. Install a support system for your plants before planting to reduce potential damage to the plants.


When planting the cannabis plants into the ground, remove some of the bottom leaves and bury the stems deeply. Roots can grow down the entire length of a cannabis plant’s main stem. The more stem that is buried, the stronger the plant will be. This is especially important for plants grown outdoors to stabilize them during heavy winds.


Tools You Will Need