The Science of Cannabis Growth: Understanding the Biology Behind Plant Development

The Science of Cannabis Growth: Understanding the Biology Behind Plant Development

Cannabis falls under the genus Cannabaceae family. It includes three species: Cannabis indica, C. sativa, and C. ruderalis. Each cannabis plant is either male or female with feminized cannabis seeds. 

Sadly, this plant fell victim to false, politically correct science that banned and demonized it. The good news is that different nations are getting out of that dark cloud and legalizing its original use. By the end of 2023, Canada, Uruguay, and 21 American states had legalized it for recreational use, while 36 other nations had legalized it for medical use. 

So, what science and biology regulate its growth? This post examines and demystifies the biology behind cannabis growth. 

Growth Requirements 

The Science of Cannabis Growth: Understanding the Biology Behind Plant Development

You must understand growing requirements before planting the best cannabis seeds. Cannabis is a facultative short-day plant. Thus, growers can use long photoperiods during propagation and vegetative growth phases to induce flowering using shorter photoperiods. 

However, research reveals that inducing flowering depends on age and internal signals, rather than photoperiods, control the plant. Other research findings show that cannabis has varying architectural and inflorescent termination. That means under some circumstances, you may consider it a day-neutral plant. Below are the conditions necessary for cannabis’s flourishing. 

Growth Medium

You need soil to grow your cannabis unless you opt for hydroponics or aeroponics. 

  • You need nutrients containing essential elements like nitrogen, phosphorus, and potassium; 
  • Your plants require a soil pH between 5.8 and 6.5. 


After buying your cannabis seeds for sale, ensure they have an optimal day temperature between 24 and 30 °C (75 to 86 °F). Temperatures above 31 °C (88 °F) or below 15.5 °C (60 °F) may decrease THC potency and slow growth. With temperatures of 13 °C (55 °F), your plants undergo a mild shock, although some varieties can temporarily withstand frost. 


Cannabis requires light to grow. You can use sunlight or artificial light when growing your plants indoors. Artificial lighting lets your plants enjoy light for 16–24 hours and darkness for 0–8 hours. However, cannabis only needs thirteen hours of continuous light to remain vegetative.


Cannabis requires water to grow and survive. You must water your plants regularly depending on light, temperature, size, age, growth stage, and a growing medium’s water-retaining ability. 

Insufficient watering causes leaf wilting, while excess watering can kill the plants because it hinders oxygen’s entry into the plants’ root system. Overwatering makes anaerobic bacteria accumulate because of waterlogged, stale conditions. They slowly start consuming plant roots, beneficial (aerobic) bacteria, nutrients, and fertilizer. When growing your plants in soil, our experts at website recommend allowing the soil to dry fully before re-watering. 


Humidity is essential for healthy plant growth because dry conditions slow photosynthesis rates. Your plants require optimal humidity levels of 40–60% RH. 


When you buy cannabis seeds for growing, pay attention to essential macro and micronutrients. Plant roots take up nutrients from the soil. You may add organic or chemical fertilizers to your soil if nutrients are depleted. These fertilizers can be powder or liquid and contain various ingredients. 

Commercial fertilizers indicate NPK (nitrogen, phosphorus, and potassium) levels. Generally, cannabis requires more nitrogen than potassium and phosphorus during all life phases. Your plants also need other trace or secondary nutrients like calcium, magnesium, and sulfur. 

Cultivation Systems

You can cultivate legal cannabis in different cultivation systems based on the existing indoor, outdoor, and mixed light regulations. These three growing systems may significantly affect the growing environment in various ways. For instance, mixed-light and indoor cultivation systems need higher external inputs like fertilizers and energy. These systems also produce higher yields and reduce environmental degradation concerns. 

Inversely, outdoor cannabis farming needs fewer inputs, although poor management or siting can degrade the environment. All growing systems can pollute the air because of their biogenic volatile organic compounds (BVOCs) that can be precursors to ozone formation. 

Regarding practice, countless variations and combinations exist across production systems. For instance, in single farms, you can keep mother plants indoors and do the cloning in a mixed-light setting, where full plants grow outdoors. 

The Cannabis Life Cycle

Cannabis has a four-stage life cycle. This section examines these stages in depth. 

Germination Stage

This phase takes two to three weeks. A plant gets sufficient nutrition from its seed to feed it for this period. Cannabis seeds are stored in cool, dark conditions that can keep them viable for years. When kept well, these seeds remain dry and hard, keeping the color of light to dark brown. Underdeveloped seeds are usually soft with a green or white pigment. 

Seed germination occurs by planting seeds in moisture seedling starter mix covered with plastic and placed on heat mats. Using a seed-starting mix instead of potting soil is a better option. 

Seedling Stage

Depending on environmental factors and seed strain, this stage can last three to six weeks. During this phase, seedlings focus their energy on growing roots and foliage. Since the roots are small, don’t overfeed or overwater your seedlings. Utilize a fertilizer high in nitrogen and dilute it to avoid harming your plants.

Fluorescent lights work well during this stage. You should set your timer to keep the lights on for 18 hours and off for six.

This level exposes your seedlings to pests and diseases. Therefore, it’s the best time to apply a preventative neem oil treatment. Remember, preventing spider mites and powdery mildew is better than treating them when your plants are still young. A spider mite or mildew infestation/infection at this delicate stage can stress your plants and reduce their yield capacity.  

Vegetative Stage

This phase can last one to four months. Here, your seedlings start outgrowing their starter pots and demanding more light and food. Moreover, their foliage and roots grow fast, allowing the plants to take in more carbon dioxide and nutrients. Don’t be surprised if your plants grow by two inches in a day. 

Moreover, this stage is ideal for identifying whether your plants are indicas or sativas. The former plants are shorter and bushy, while the latter are slim with less foliage.

Flowering Stage

This phase lasts from week six to ten, depending on your strain. You must expose your plants to an equal darkness and light period of 12 hours each. Your plants begin to bloom to procreate before dying at the season’s end. Your cannabis produces a sweet-smelling, sticky resin coating containing THC and terpenes.


Cannabis’s growing legalization has opened the door for its cultivation for medical and other uses. This post discussed the biology and science behind its cultivation. The ball is in your court to use this invaluable information to improve your cultivation quality and yields. 

The article’s author, Tia Moskalenko, is a dedicated cannabis writer at AskGrowers specializing in conducting interviews with renounced cannabis brands. She had a chance to work in different industries, but cannabis caught her attention for good. 

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