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The Science Behind Growing Cannabis


The Science Behind Growing Cannabis

Every cannabis consumer and grower should learn the science behind cultivating marijuana plants. The fascinating stages and incredible processes cannabis goes through will give you a whole new appreciation for the plant.

How does cannabis grow and what’s the science behind the different stages? Marijuana is an incredible plant, and the way it grows is a miracle of nature. The scientific processes behind germinating seeds, growing cannabis, and drying buds is remarkable. Cultivating cannabis is truly an art and a science.

Different Types of Cannabis

Not every marijuana plant is structured the same. Different strains and species will have unique physical traits and varying levels of cannabinoids, terpenes, and other compounds.

Cannabis Sativa is one variant of marijuana known for producing uplifting effects. These plants are thought to have originated from near the north of the Himalayas in eastern Asia. Sativa strains are long and tall, commonly growing between 4-12 feet in height. The fan leaves arrange themselves like the fingers in your hand and spread out from the center of the plant. 

The other popular variety of marijuana is Cannabis IndicaThis form of cannabis is known for its sedative effects, making it an ideal choice for medical use. Indica plants tends to be shorter, and produce small, dense buds. When this variety of marijuana is grown outdoors, the plants will bloom in the late summer to mid-fall. Indica plants can comfortably be grown indoors as well.

Aside from the two primary forms of marijuana, there are also hybrids and hemp varieties. Breeding indica and sativa plants together creates hybrid cannabis strains, which are the most common variety in the world. Cannabis Ruderalis, the final type of marijuana, is unique because it produces almost no THC. This cannabis variant won’t get you high, but it may have medical benefits thanks to high concentrations of CBD.

Cannabis Plant Growth Cycle

Some varieties of cannabis have short growth cycles, while others take much longer. Typically, sativa strains have a longer flowering period than any other type of cannabis. Meanwhile, some ruderalis strains are auto-flowering, meaning they produce flowers only 21-30 days after being planted. It all depends on the strain and variety of your plant, which is determined by the DNA in the seed.

Variables That Affect Growth

How often you water your cannabis plants is a huge factor in determining how quickly and healthily they grow. Even the first stages of dehydration will cause wilting leaves and stunted growth. But be careful, since over-hydration can cause the soil to become waterlogged, resulting in increased chance of plant death. 

Another significant variable that will impact your growth rate is the quality of your soil. Cannabis plants need nutrients like nitrogen, magnesium, calcium, and sulfur to grow. These nutrients may be added via fertilizer if the soil is depleted, but be careful not to overdo it. Too many nutrients can cause your plant to ‘burn’ and become unhealthy.

The exact cocktail of nutrients needed will depend on plant variety and climate. Typically, cannabis needs more nitrogen than any other secondary nutrients. Micronutrients like iron, boron, manganese, zinc, copper, molybdenum, and chlorine are important, but rarely an issue. Other variables that may affect your harvest are the size of your grow area, light exposure, and temperature.

Cannabis Seeds & Germination

Cannabis plants can be either male or female. Seeds are produced and dispersed when these two sexes reproduce. However, if reproduction occurs, the plant won’t produce THC-filled buds. For this reason, only unseeded female plants are valuable to growers. Female cannabis plants selected for marijuana production are kept isolated from the males.

Once you expose the cannabis seeds to water and light, the process of germination begins. At this stage, the hormones become activated within the seed. The root will grow stronger and break open the seed’s shell. After this, the stalk will begin to form along with two embryonic leaves, called cotyledon leaves. Once these leaves show up, large-scale cell division and rapid growth will begin. At this point, a grower can create clones if desired.

Important germination tips:

  • The pH of the soil needs to be between 5.8 and 6.5 PH
  • Artificial light for 16-24 hours and then up to 8 hours of darkness is recommended
  • The periods of light influence leaf growth, the time of darkness is for flowering

Stages of Cannabis Plant Growth

Sprouting & Seedling

Once the seed has germinated, rapid growth will cause the marijuana plant to sprout. In the sprouting stage, moisture is absorbed into small, porous openings on the seed called camicropyles. This causes the seed to grow and sprout.

As it becomes free from its shell, the plant will start pushing outwards and up. The sprout will need continued moisture to survive at this stage. Monitor the temperature, air flow, and light exposure. The process of sprouting is the shortest stage in the cannabis plant lifespan. 

The root system then begins to develop rapidly and spreads out to the top of the plant. These roots will turn into the well-known fan leaves. At this point, the cannabis plant is considered a seedling. This phase can last 3-6 weeks, depending on the strain and other variables. The temperature at this stage should be 75-86°F during daylight hours, with humidity ranging between 40% RH to 60% RH.

Vegetation & Flowering

As the marijuana plant grows taller and stronger, light exposure becomes critical. A healthy plant can grow 2 inches every day! The developing roots will absorb large amounts of nutrients and CO₂ during this vegetative stage. Next is the flowering stage, when cannabis plants begin producing the cherished buds. This is, of course, one of the most exciting stages for growers.

During the flowering phase, the marijuana plant will need less light. This should occur naturally for plants that reside outdoors if they’re in proper conditions. If you are growing cannabis plants indoors, be sure to manually decrease overall light exposure. The flowering stage produces loads of THC and sticky resin on the outer leaves and buds. 

Most strains will take 6-10 weeks to fully flower. To get the most out of the marijuana, it’s essential to allow this stage to run its course. The flowering stage will be done when 70-90% of the trichomes on the buds transform into a more brown color. The broad leaves will change from a dark green to a light yellow-green. Following the flowering stage, cannabis plants are ready to harvest.

Drying & Curing Buds

Marijuana flowers need to be dried under the ideal conditions to preserve terpenes and fend off mold. A dark space with a temperature between 60-70°F and a humidity of 45-55% is recommended. Hang the flowers until dry; this could take several weeks to achieve ideal results. 

The first few days will produce a discernible aroma, thanks to the terpenes and terpenoids. These compounds bind to receptors in your endocannabinoid system and produce smells like lemon, pine, and cinnamon. 

Once the marijuana buds are more than 60% dry, begin the curing process. Be cautious of mold forming at this stage. Pack the cannabis nugs into airtight jars to cure for 30 days in a cool, dark place. In some cases, proper curing can take up to 6 months. Curing cannabis makes the weed more pleasant to smoke. 

Understanding Marijuana Plants

Understanding the science behind growing marijuana can make you a better grower and more aware consumer. Cannabis is an amazing plant that goes through fascinating stages and processes. The earliest evidence of cannabis use reveals that people have been growing weed for over 2,000 years, so it’s no surprise that we’ve mastered many of these growing phases. Learning how to germinate seeds, grow cannabis plants, and cure buds is empowering and exciting. Every cannabis consumer should educate themselves on the science behind the plant.


Philip Ghezelbash is passionate about presenting complex science in an easy to digest manner and is a firm believer in the power of cannabis. As an ex-personal trainer, science graduate, best-selling author, and freelance writer, Philip has helped educate millions of curious people around the world about science-based health, nutrition, and fitness.


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