The vast majority of cannabis growers cultivate the plant to produce sensimilla . Sensimilla refers to female cannabis buds that have not been pollinated by a male cannabis plant. Sensimilla is more potent than seeded cannabis as it contains greater concentrations of essential oils and psychoactive cannabinoids.
Female plants are generally shorter, denser in foliage, and broader than their male counterparts. Photo by: Gina Coleman/Weedmaps
How can growers prevent hermaphroditic plants?
Like all plants, however, cannabis has an inherent drive to procreate by propagating seeds. One way that the plant achieves this is by herming, when female plants become hermaphrodite to self-pollinate. The tendency to herm means that growers must take extra care to minimize any stressors that may cause the plant to perceive a threat and change its sex.
To a non-expert grower, all cannabis seeds look alike. The gender of cannabis plants becomes more readily apparent when the plant approaches the flowering period .
“We found that it is better to remove the entire plant than cutting off the problematic branches,” explains Perlowin. “We do this by using a large plastic bag to cover the entire plant. Without shaking the plant, we move the bag down to the very bottom of the plant, seal it, cut the plant down at dirt level, then take it off the property.”
When growing marijuana outdoors, a grower doesn’t need to do anything to induce flowering because the sun will take care of things on its own. All you need to do is make sure your plant isn’t directly under a street light or other light source, so that the plant receives complete darkness at night.
When marijuana plants are seedlings (or when they’re just seeds), there’s no way to tell which plants are male and which plants are female.
Pre-Flowers usually reveal the gender around week 6 from seed, or you can wait until the plant switches to the flowering stage.
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In fact, with marijuana plants, the length of night period, not the length of day period, seems to make the biggest difference. This makes sense if you consider that in the wild, a stormy or cloudy day could shorten the light period a plant receives, but few things in the wild will interrupt the darkness of night.
But ANY 12 hour dark period will work, as long as you prevent your plant from getting light leaks during their “night.”
Next, cannabis plants switch to the flowering stage which means they stop growing bigger and taller, and instead spend all their effort growing flowers (the buds we want are flowers!). The flowering stage is like the “adult” stage of a cannabis plant since at this point it’s only interested in adult stuff like growing their male and female parts, then pollinating 🙂 In the flowering stage, plants start growing buds or pollen sacs in earnest. The buds we want are female flowers, so growers generally only want to grow female plants.
Among the early signs that your female has been pollinated is that her bracts become larger. Bracts are small, leaf-like structures that protect the female’s reproductive parts. These are the sites from which the flowering buds appear. Do not confuse the bracts with calyxes.
Obviously, no one wants to smoke seedy weed. When you grow cannabis and learn how to identify male plants and signs of pollination, you can remove these plants to save your remaining females. Likewise, recognising a pollinated female early allows you to start again before it’s too late, rather than finishing a grow that will only result in a poor-quality harvest.
HOW TO AVOID POLLINATION OF YOUR FEMALE PLANTS
There is a good reason why most growers keep male plants away from their ladies: Pollination from males causes the females to develop seeds. As a result, females focus their energy on seed production, rather than on growing you some fine-quality bud. This seedy and unfortunate final product can be avoided by implementing a few basic techniques.
Pollination requires the presence of males or intersex (hermaphrodite) plants, which are females that will also produce pollen. The first thing you want to do to keep the risk of pollination low is to remove as many males or “hermies” as as you can. Especially during the first three weeks of flowering, it’s important to frequently check for possible male specimens in your garden.
Another indication of pollination can be the colour of her pistil hairs. When a female has been pollinated, the previously white hairs will soon shrivel and become darker.