In the wonderful world of weed, male and female plants are not created equal. After all, it is the female plants that produce the cannaboid-rich flowers that consumers desire. The males are relegated to supporting roles. In nature, marijuana plants will produce both male and female seed in relatively equal portions, which in the early days wasn't the greatest news for cultivators. There's simply no way to tell visually which are male and which are female, so if you were a grower back then you would have had to plant crops with the understanding that only about half of them would yield flowers. It was a real bummer.
As you've likely guessed, this 50/50 outcome was highly inefficient. Whether cultivating plants for medicinal or recreational use, growers with regular seeds had to plant twice as many plants to hopefully get the harvest they desired. In most cases, weed plants don't begin to display their sex until they have matured beyond the vegetative stage. This meant a grower had to use twice as much space, twice as much fertilizer and nutrients, and if growing indoors, they would have had to spend twice as much on electricity for half the yield. And the grower would have had to monitor plants closely to make sure the male plants were removed before they could pollinate the females.
That all changed in the 1980's when a Dutch geneticist by the name of Henk van Dalen, founder of Dutch Passion seed company, produced the very first feminized seeds, those that with near 100 percent accuracy would develop into female plants only. If the laws in your area restrict the amount of weed you can grow, you owe a lot of thanks to Henk van Dalen.
Now, before we discuss van Dalen's work, we'll need to hold a small refresher course.
Cast your memory back to your middle school sex education classes, and you may recall the lesson on XX and XY chromosomes. The egg produced by the female always has an X chromosome, but each male sperm has either an X or a Y. If the egg is fertilized with sperm carrying an X chromosome, then the fertilized egg will have a pair of XX chromosomes and develop into a female child. A fertilized egg with a pair of XY chromosomes will develop into a male.
Hopefully you paid attention, as this will be important later.
In respect to chromosomes, humans and weed aren't all that different, but they part company in a big way when you mess with their sex lives. While cannabis plants can be male or female, it is not uncommon for plants in the wild to become spontaneously hermaphroditic, meaning they develop characteristics of both sexes. This is likely an evolutionary survival mechanism to ensure they can self pollinate and continue the species if one sex, or the other is not readily available.
It was this natural trait that got van Dalen to begin experimenting with female plants. He found that by allowing them to flower too long without pollination, some of them would become stressed and develop miniature male pollen sacs. The geneticist then took that pollen and used it to pollinate other female plants. Surprisingly, the plants that these newly pollinated females produced were all females. Subsequent repeats of his experiments resulted in female plants only. It was an amazing breakthrough in biological engineering.
Henk van Dalen had figured out how to create--not female, but rather, feminized seeds. He wasn't the first to do this, but he was the first to do it with cannabis. While the stress he put on the female plants caused them to develop male characteristics, he had not changed the genetic composition of the plants. They were still female, and so the pollen they produced had no Y chromosomes. As a result, the pollination between the reversed female and the female plants would always result in XX or female off-spring.
As van Dalen learned, it is the introduction of stress that causes some female plants to become hermaphroditic. Common stressors include changes in light and temperature, fluctuation in pH levels, and changes in hormones provided. Plants may also be stressed by over-fertilization or too little or too much water. While both male and female plants can develop traits of the opposite sex, the development of a reversed female plant is much more common.
When it comes to breeding, one of the concerns early on was that the hermaphroditic plant with the donated pollen might pass along its tendencies to the new seed. This was extremely undesirable as introducing the possibility of male plants into a crop could potentially destroy an entire harvest.
Over the years, modern breeders have learned that while some female plants become hermaphroditic quickly, others, no matter how much stress they are exposed to, will not easily develop male characteristics. It is the latter of these two types of plants that are today chosen for the development of reverse female plants with male flowers. By utilizing these resistant weed plants, the resultant offspring was far less likely to become hermaphroditic.
We've come a long way in the development of feminized seed since van Dalen's earlier work, and today there are a number of tried and true methods. What has been learned is that in order to bring about a "sex change" in marijuana plants, one needs to reduce the amount of ethylene in plant tissues. This forces the development of feminized pollen-producing male flowers during the flowering stage.
Modern methods include spraying female plants with different solutions, typically a blend of water and fine silver particles that impede ethylene production. Various solutions include silver nitrate and sodium thiosulphate mixed with distilled water, or a solution made with distilled water and collodial silver. If you want to try this for yourself, whichever solution you use, just be sure to discard the sprayed plants once you harvest the pollen. The use of gibberellic acid, also known as GA3 is another method useful for growing cannabis seeds. Like the silver solutions, it is sprayed on the plants for a number of days before changing the photoperiod of your plants over to flowering.
Today, nearly everything on the market is feminized. The feminized product offers a far more practical and efficient means to grow weed. The only problem for growers is that they don't produce male plants, so they have to try growing cannabis seeds themselves. In a way, it's opened a door to a whole new breed of geneticists.