It is only when you truly study the marijuana plant that you begin to understand the various parts of its anatomy. There are plenty of people who know when they grow a good batch and can tell the difference between an indica-dominant hybrid and a sativa-dominant one.
However, not all of these experts are acquainted with the plant’s anatomy. For example, you have the:
- Cola: The flower that develops at the end of any branch. The term ‘cola’ is also used to describe the largest bud that grows on the top of the main stem.
- Bract: These green leaves have a teardrop shape, and are covered in resin glands.
- Calyx: This is the bud itself, and features a concentration of sugar leaves, so-called because of the immense covering of trichomes.
- Trichomes: These are tiny, bulbous globes which contain cannabinoids such as THC and CBD, along with aromatic oils known as terpenes.
- Fan leaves: These enormous leaves are part of the harvest and are often used to create edibles.
- Nodes: Marijuana grows on skinny stems, and the fan leaves extend out from the nodes.
If you understand cannabis anatomy reasonably well, you’ll realize that we’ve left out an important component.
The answer to the title question is: “stigmas.” A pistil is a female cannabis sex organ, and the tiny hair-like strands that protrude from it are called stigmas. Stigmas collect pollen from male marijuana plants. Once these hairs come into contact with male pollen, they become pollinated. Initially, the stigmas of the pistil are white, but as harvest time approaches these hairs begin to get darker and progress from yellow to orange, then red, and finally brown, depending on the strain.
When pollination occurs, the pistil develops a seed, and the plant’s life cycle has been completed. Although it plays a major role in reproduction, as a grower you don’t want this process to occur. Once your female plant has been pollinated, it develops seeds and moves its focus away from producing resinous flowers. As a result, your weed will be less potent.
Pistils & Young Cannabis Plants
In general, young male cannabis plants develop preflowers before females. You can confirm that your feminized seeds are actually female in the first 3-6 weeks after germination. If you purchase regular seeds, you can spot whether or not they are male at this point. As pistils can poke out randomly from young marijuana plants, you should inspect them carefully to spot preflowers quickly.
On the stem, there will be a stipule, a green ‘hair-like’ growth from which you should see the preflowers. If you see a white hair emerging from several nodes, you have a female plant. Depending on the strain, it could take up to eight weeks of vegetative growth to confirm female plants, which is why we recommend purchasing feminized seeds from a reputable seller.
Pistils & Mature Cannabis Plants
If you spot a male plant, remove it from your garden as soon as possible before it pollinates the rest of your crop. The stigmas in the pistils are long hairs and can help you determine when a plant is ready for harvest. In the first few weeks of flowering or when a bud is formed, you should see numerous white hairs coming out of it. For the first 4-5 weeks, the stigmas will remain white. Eventually, you should spot a yellowish color forming.
The actual color you will see depends on the strain. For example, the stigmas may remain yellow until harvest time, or turn red, amber or dark brown. For new growers, this is a tricky period because you need to time your harvest correctly. If nothing else, make sure that at least 50% of the stigmas have changed to a yellow/red/brown color before considering harvesting the crop.
Experienced growers wait until 70-80% of the stigmas have changed color. It is at this point that the buds are likely to be at their most potent. We recommend purchasing a magnifying glass to check the crop’s trichomes. If three-quarters of the stigmas are red and a majority of trichomes are milky white with a bulbous mushroom head, your plants are ready to harvest.
If you wait too long, the stigmas will become dark brown and start to dry out. Although the weed will still get you high, some of the THC has degraded into CBN by this point, which means the taste and overall potency will be negatively affected.
The majority of the cannabinoids, such as THC and CBD, that you find in a cannabis plant are located in the pistils and calyxes of the plant. This is known as the flower part, which is harvested, dried, cured, and consumed. Incidentally, if you continue to grow your female plants after they have been pollinated, the seeds become a pain to remove. If you leave the seeds in your weed, expect a harsh and unpleasant smoking sensation, with coughing fits likely.
Although the following can differ depending on the strain, as a rule of thumb the stigmas remain white for 4-5 weeks into flowering. At this stage, your plants are typically halfway through flowering, and you will see the first change in color. It isn’t until weeks 7-10 where you will notice a substantial number of orange, red, or yellow hairs.
Both female and hermaphroditic plants display pistils and stigmas, but ‘hermies’ also produce pollen and threaten your female plants. It is also important to remember that stress can cause a female plant to develop intersex traits.
Final Thoughts on the Red Hairs on Cannabis
The red hairs you see on cannabis are called stigmas and are part of the pistil. Although it is not always the case, high-quality bud tends to have pistils with a lot of hairs. When your weed matures, the color of the pistils’ hairs change. At first, these hairs are white, but as your marijuana approaches maturity, the color changes to red, yellow, or brown. As the pistil matures, it dries out and begins to curl. Once at least half of the hairs have turned red, it is time to consider harvesting your crop.