Growing cannabis may seem simple, but modern-day cultivation for medical applications is a rigorous process. It can take anywhere from 10 to 32 weeks to harvest and involves multiple growth stages, each requiring the manufacturer to nurture the plant differently.
Understanding these growth stages and the steps a licensed grower takes to produce medicinal cannabis products can help shed light on how this medicinal plant is.
Propagation, or germination, is the first part of the cycle, lasting anywhere from 3 to 10 days. At this stage, a seed will go from hard and dry with a light- to dark-brown colour to a sprout that’s ready to be placed in soil.
At first, two rounded leaves will grow from the stem. These first leaves play an essential role, breaking free from the protective casing for the seed and starting the photosynthesis process—in other words, processing sunlight so the plant can grow.
After this, the stalk will start to rise, and the first signs of the fan leaves appear. This is when the leaf begins to resemble what most people see when they envisage a cannabis plant. It’s an indication that the next phase of growth is beginning.
2. Seedlings and Clones
After the propagation period, you’ll have a seedling that will develop more leaves and individual blades per leaf over the next two to three weeks. Leaves typically have five to seven blades, but some can have up to nine—the seedling graduates to maturity when the total number of blades appears.
Since seedlings are quite vulnerable, many growers will start their seeds inside speciality environments under artificial light to protect them from disease, mould, and other environmental aggressors.
In some cases, a clone will be used instead of a seedling. A clone is a cutting from a mature cannabis plant (the mother), which can grow into another complete plant (the replica). The benefit is achieving better batch-to-batch consistency in the cannabinoid profile and content.
A report published in Frontiers in Plant Science in 2020 explains, “Once high potency mother plants are identified and selected based on their cannabinoids profile they are multiplied asexually, yielding identical clones using conventional (vegetative cutting) and/or biotechnological tools (tissue culture) to ensure a batch to batch consistency in the final product.”
3. Vegetative Stage
When the time comes to move a seedling or clone into a larger pot to make way for outward-growing roots and quickly develop foliage, the plant has reached the vegetative stage. This period can last anywhere from 3 to 16 weeks and will be marked by a significant increase in size.
Like any living thing, a cannabis plant requires nutrients for healthy growth. This includes nitrogen (N), phosphorus (P) and potassium (K), the three nutrients most plants need.
In the case of cannabis, nitrogen is vital, with studies showing “the optimal N supply for both vegetative and flowering stages of cannabis production using conventional fertilisers is approximately 160 mg L–1.”
During this stage, the plant also requires plenty of water, especially for the roots. As the plant begins to bush outwards and upwards, some producers will use string, rope, or netting to train their plants to get higher yields or simply provide support as they grow. This practice is referred to as scrogging, topping, or training.
4. Flower Stage
Now that a large, healthy plant has grown, growers shift the light schedule to trigger the flowering period.
Flower is the goal, as these resinous buds are later used to make medicinal cannabis products. In most plants, the flowering stage will occur when there is less light throughout the day and will last 8 to 9 weeks. But some strains can take even longer.
This period is broken up into three sub-stages:
Flower initiation (weeks 1 to 3): At this stage, the flower will produce white, hair-like structures called pistils. These contain the female plant’s reproductive organs and will eventually develop into buds.
Mid-flowering (weeks 4 to 5): Buds increase in size, and the plant stops growing.
Late-flowering (week 6+) Plants will get sticky and smelly, and the previously white pistils will turn red or brown.
At this late stage, the buds will be covered in trichomes, which are responsible for secreting tetrahydrocannabinol (THC) and other cannabinoids. These trichomes will turn from transparent to opaque and then amber, indicating that the plant has reached peak maturity.
The harvesting process will begin when the producer notices tell-tale signs that their plant has fully matured. This process starts with chopping down the plants and hanging them to dry for several days.
The drying process is crucial as it helps retain terpenes and cannabinoids while ensuring the plant does not mould. But, there are lots of variations in the drying process, and some products are flash-frozen immediately after harvest and then go through a freeze-drying process.
In a systematic review of post-harvest operations to generate high-quality medicinal cannabis products, it was found that “vacuum freeze-dry is considered the best method to retain a maximal number of active phytochemicals, preserve the quality of terpenes, and is a safe method to develop medicinal Cannabis products that takes only a short time.”
For conventionally dried cannabis, the buds get stored in airtight containers to stop moisture loss and preserve the plant. They’ll stay here to cure, which can take two weeks to a month. This process further locks in the terpene profile and helps manufacturers store the plant for long periods without risk of degradation.
It is only at this stage that manufacturers can then go on to create oils, tinctures, and other products for medicinal cannabis patients.
Growing Cannabis in Australia
Growing cannabis in Australia is regulated by the government’s national licensing scheme under the Narcotic Drugs Act 1967. Any person or business growing cannabis requires a medicinal cannabis or cannabis research licence and permit. At the time, it is illegal to grow cannabis at home, even if you have a medical cannabis prescription.