Ultimate Plant Sexing Guide
By Rellikbuzz from Breedbay
When compared to most plants on Earth, Cannabis plants are quite unusual but not unique in respect to the fact that there are seperate male and female plants within the species. They are Dioecious plants. Meaning that the male and female sexes are expressed in seperate plants. The largest percentage of fruit or flower bearing plants contain both sexes in the same plant. Therefore, they self-pollenate with the assistance of insects carrying the pollen to the female pistillate (ie, tomatoes, peppers, flowers, etc.). There are anomolies within the genus of Cannabis plants, called Hermaphrodites, that also contain both the male and the female organ but we'll address this more indepth in a moment.
Outdoors in nature, female Cannabis plants are pollenated by male pollen carried by the wind. Most all other plants are pollenated by insects that are drawn to plants by brightly colored flowers. Not the case with Cannabis. Upon release of the pollen by the male plants, the wind can spread the pollen for miles. One male can produce enough pollen to pollenate thousands of female plants within several hundred feet of the male's proximity.
Why is it important to know the sex of my plants?
Good question! Male plants, while crucial in the natural reproductive process, are only useful in breeding Cannabis plants (by harvesting pollen from choice, select male plants) and for it's fiber. On the other hand, female plants produce the euphoria enducing THC resins (Delta 9 Tetrahydracanabinol) sought after by Cannabis enthusiasts and for medical patients seeking it's pain-killing and healing properties.
Unpollenated females will produce prolific amounts of flowers that form into elongated spears known as "colas" that contain copious amounts of the aforementioned THC cannabinoids. These unpollnated females are known as Sensimilla (pronouned "Sin-Se-Mee-Ya", a spanish term meaning "seedless" or without seed) and are the most potent, desired and valued form of Cannabis. If allowed to remain unpollenated for their entire life cycle, these plants are able to focus their growth hormones and energies toward the production of female Pistillate (the female organ) and toward the production of trichome glands (which contain the THC layden resins). Once pollenated, the female plant focuses it's energies on producing seed. Therefore, the yield of consummable cannabis is signficantly decreased in a pollenated female and the potency is lessened by comparison. By culling the males from your garden prior to pollenation, the resulting females will blossom into the highly coveted Sensimilla.
To fully understand the process of sexing your plants, we must first look into how cannabis sexually matures and procreates.
The Reproductive Process
Just like all annual fruit bearing plants, Cannabis plants are genetically programmed to reproduce to carry on it's own genetic lineage through it's off-spring, the seed. This dire need to reproduce can be seen in some strains of female plants that late in flower will, even in the absence of male pollen, produce it's own male preflowers in a desperate attempt at self-pollenation to continue it's lineage. These plants are not deemed Hermaphoditic (possesing both male and female sexuality) but do show that a plant will go to all measures to reach it's goal of being pollenated and developing seed. Even by developing it's own pollen sacs.
There are three major phases of growth for all fruit bearing Dioecious plants (having seperate male and female plants). They are:
* Seedling Phase
* Vegetative Phase
* Flower or Bloom Phase
It is inbetween the latter part of the Vegetative Phase and/or the early part of Flower/Bloom phase that Cannabis plants mature sexually. This most often occurs after the onset of Alternating Phyllotaxy. In early stages of vegetative growth, new leaf sets at every node will be parallel to each other. Meaning that the leaf stems (petioles) attach at the same point on the main stem (meristem) when compared to the nodes just above and below. When the plant begins to sexually mature, these leaf sets at one node will be perpendicular (90 degree angle) to the one's just above and below that node. When you begin to see this alternation of leafsets (Alternating Phyllotaxy) from one node to the next, you're plants will be showing preflowers very soon!
Most books and general grow literature you will read will state that you cannot tell the sex of a plant until you are one to two weeks into the Flower/Bloom phase. This is simply NOT true! While not categorically the case, most seed plants will show their Preflowers in the late Vegetative Phase at about 4 to 6 weeks from seed. Even prior to implementing a flowering light schedule. Having said that, this is certainly a strain specific topic. As an example, while an Indica or Indica/Sativa hybrid might show preflowers prior to actual flowering, it may take a long-term Sativa like a Thai or a Haze three to four weeks into a 12/12 light schedule before preflowers are at all detectable. Although rare, you will find the stubborn strain that simply will not show preflowers until the 12/12 flower lighting regime is implemented.
What are Preflowers?
Upon reaching sexual maturity, Cannabis plants will display their "Preflowers" which, essentially, are the first showing of their respective sexual organs. In the earliest stages, these preflowers are almost indetectable to the naked eye and therefore it won't be easy to tell the difference between a male and a female early on.
How do I find these Preflowers?
Initially, the top two or three nodes near the top of the plant, BELOW the highest node (the point where the leaf stems attach to the main stem/meristem), is where preflowers typically appear first. You will need the aid of a magnifying glass or jeweler's loop to actually see them. A 30x magnifier like this one from Radio Shack will do just fine to bring them into sight. They sell for only $8.95.
Focus your attention in the "crotch" of the leaf stem (petiole) and the stalk (meristem). When the plant develops it's preflowers, this is where you will find them. The next diagram gives a good breakdown of this area of the plant.
The Staminate Primordia indicates the male preflower and the Calyx represents the Pistillate Primordia of the female plant. However, note that both the male and female preflowers appear in the same location at the "crotch" area located on the top side of where the Petiole meets the Meristem. Also note that the spear-shaped leaves called the Stipules are NOT the preflowers. This is a common misconception that some have about sexing plants. Some people mistakingly believe that if the Stipules "cross" or point towards each other that this indicates a female and if they point away from each other that would be a male. This is a fallacy. Only the actual preflowers will indicate the sexuality of your plants. The following chart shows the male and female preflowers in a side by side comparison from earliest form to fully maturity.
Note that upon maturity, after the release of pollen, the male staminate literally resembles a flower.
It is important when growing Cannabis to evaluate what your goals are in growing. Are you growing for euphoric or medicinal needs or are you planning on breeding Cannabis? Only in the latter instance will male plants have any usefulness in your garden. Further, it is important to realize that when growing Sinsemilla (seedless female plants) that we are interrupting the reproductive process of the plants for our benefit. We are denying the females the procreating pollen that they desperately seek in order to reproduce. The genetic goal of these plants is to reproduce and further their species but we must prevent this in order to assure ourselves of having those female bud clusters we all desire.
The Male Plant
In general, male plants will be the first to show their preflowers in advance of their female couterparts. This should be a sign to to the grower to watch these plants closely as you will want to cull these plants from your grow if, indeed, they do end up being males. Another notable trait amongst male plants is their tendency to "stretch" and have a general overall taller stature when compared to female plants at the same stage of growth. They will most always be amongst the tallest plants in the garden at any given stage of growth. So, this should also serve as another warning flag to pay particular attention to these plants as they may, indeed, be male.
It is prudent to mention here that what at first might appear to be a male, can and does often end up being female. So, the bottom line is, don't rush to judgement. You have some time before the males will release their pollen and it can pay to be certain before jerking a plant out.
Additionally, male plants will tend to grow "spindly" and sparce in comparison to their female counterparts. The internodal spacing (distance between set of leaves on the main stem) will generally be much wider while the female will have lush growth with much tighter internodal spacings. Here's a full plant shot of a typical male plant. Note the spindly growth and the wide internodal spacings.
At the first signs of preflowers, it is nearly impossible to tell the difference between a male and a female plant. Initally, it will just appear like an indiscernable lump or growth in the "crotch" between the petiole and the meristem.
At this point, the preflower hasn't developed enough to identify the sex of this plant. Here's another that also shows an undetectable preflower.
Photo Courtesy of Small Potatoes
Within a few days to a week or so after the first emergence of preflowers, you will see the Primordia of both the male and the female plants start to change and become more individualistic. As such, this is the time you will be able to recognize the differences between the male and female plants.
In an attempt to describe the sexual organs of plants more vividly, you will hear terms like "Balls" and "Hairs" meant to describe the preflowers of the male and female plant, respectively. In the case of male Primordia, this is fairly descriptive. At the point where male preflowers take on their eventual appearance, they do look like little balls. However, in some cases, they look like a ball on a stick. Here's a shot of a male that really illustrates the "ball on a stick" appearance of the male preflower. However, not all strains will exhibit this trait clearly.
You can see how the ball is "raised" up out of the "crotch" a bit. By comparison, the female calyx will sit down in the "crotch". This can be a fairly discernable difference between the male and female preflowers. So, growers should look for this characterisitic early on.
Photos Courtesy of Small Potatoes
Another descriptive term for the male preflower would be like the shape of a Crab's Claw. As the male preflower begins to open a bit, it will look much like a Crab's Claw. This is another characteristic of the male plant to look for to discover these early on before they can fully open and pollenate your garden.
From this point on, male and female preflowers will begin to look distinctly different. Further, the males will become more apparent as the "balls" will begin to multiply with many balls developing at each node. The balls form in "grape-like" bunches. The next pictures will give you an idea of how this looks.
The clusters of balls on the male plant also closely resemble the budding growth of the Hops plant (used in the production of beer).
The Female Plant
As their sexuality suggests, Female Plants are the "Goddesses of the Garden"! Even during the Vegetative Phase, just their mere shape and lush nature suggest they would be more shapely and elegant when compare to their male couterparts. Tight internodal spacings, symnetry of plant structure and generally shorter stature (when compared to males at the same point of growth) are characteristics of the female plant.
As noted earlier, most often male plants will display their preflowers prior to that of the female. This is an important point to keep in mind as those stubborn plants that are driving you crazy because they won't show just might be female. So, be patient with these plants! You may be rewarded with a dank, lovely female as a result. With most strains you run across, the females will still sprout preflowers during the vegetative phase if left to vegetatively grow long enough. Typically, five or six weeks from seed. Within a week or two after males begin to show, you will see the ladies chiming in with their sexuality as well.
We've already discussed how difficult it is to recognize the difference between male and female preflowers early on after their first emergence. However, shortly after, the differences are easily recognizable. With the female preflower, you will often hear folks describe it as a "Tulip-shaped pod with two hairs coming out the top it", which wouldn't be an inaccurate description. The female preflower, in fact, does look much like the bulb of a Tulip with two white hair-like follicles protruding from the top.
This next pic shows a single female preflower (Calyx) with two hairs (Pistils) poking out of the top. The pencil tip gives you an idea of how small the female Calyx really is.
Here's some more pics of the Female Preflower:
Notice in the last pic how the Calyx (the green tulip-shaped pod with the two white hairs) sits right down in the "crotch" between the leaf stem (Petiole) and the main stem (Meristem)? This is a notable difference compared to the male staminate which has the "ball on a stick" structure which raises the ball up out of the "crotch" a bit.
Once you learned to recognize the distinctly different shapes of the male and female primordia, sexing your plants will become second nature. You'll learn to instinctly tell which plants are most likely male or female just by their growth patterns and overall structure. Even before they show preflowers!
The hairs that protrude from the Calyx (otherwise known as Pistils) will grow and mulitply prolifically once placed into flower to become the frosty, resinous buds that we all know and love. Once exposed to a 12 hours on/12 hours off light schedule, the flowering hormones kick in thus causing budsites appear all over the plant.
The Hermaphrodite Plant
What is an Hermaphroditic plant?
An Hermaphrodite, or hermie, is a Marijuana plant of one sex that develops the sexual organs of the other sex. Most commonly, a flowering female Marijuana plant will develop staminate flowers, though the reverse is also true (more on this in a moment). Primarily male hermaphrodites are not as well recognized only because few growers let their males reach a point of flowering where the pistillate would be expressed.
Hermaphrodites are generally viewed with disfavor. First, they will release pollen and ruin a sinsemilla crop, pollinating themselves and all of the other females in the room. Second, the resulting seeds are worthless, because hermaphrodite parents tend to pass on the tendency to their offspring. Occassionally specious staminate flowers (aka Bananas or "Nanners") will appear in the last days of flowering of a female Marijuana plant. These typically do not drop pollen or, if they do, the pollen is often not viable and/or it's so late in flower that seeds don't have time to develop. Late appearing Staminate flowers is not considered evidence of deleterious hermaphroditism.
It is widely accepted that cannabis plants become Hermaphroditic for one of two reasons:
1. The strain is genetically pre-disposed to Hermaphroditism. OR
2. Hermaphroditism was triggered by environmental stress such as: irregular light schedule, light leaks in flower chamber during dark period, nutrient shock or toxicity, wildly vasilating pH, etc.
Ed Rosenthal on Hermaphrodite Plants: (From Cannabis Culture article)
Plants turn hermaphroditic in two ways. Some plants are programmed genetically as hermaphrodites. These plants will produce male flowers on female plants no matter what environmental situations they face. Other plants are induced to grow male flowers under stress conditions. Some plants may be more genetically predisposed to hermaphroditism under stress, but all plants may exhibit male flowers as a sign of stress created by growing conditions. This hermaphroditism is not genetic and does not affect the plant's progeny. Sometimes plants that aren't hermaphroditic outdoors will grow male flowers when grown indoors as a stress response. Stresses can include lighting regimen irregularities, low light conditions or response to hormones.
If a genetic hermaphrodite is crossed to a non-hermaphroditic female, about half of the resulting plants will be hermaphroditic. If the hermaphroditism was caused by environmental factors, then none, some or all of the progeny will exhibit male flowers depending on whether the plants have inherited a tendency towards hermaphroditism under stress conditions and whether the plants face those conditions.
If you have only a few plants and are willing to spend the time making daily inspections for male flowers, you can produce a sinsemilla crop. It's important to remove the male flowers before they open and release pollen.
Here are some shots of Hermaphrodite Plants:
As mentioned earlier, when "hermies" occur it is by far more common to see a female plant produce male Staminate flowers. However, though it is rare, the opposite does occur. It is possible for a male plant to produce female Pistillate. This anamoly is far more intriguing and compelling as it actually may have profound value in the breeding arena.
Highly respected and noted breeder DJ Short on Backwards Hermaphrodites:
A quick word on "backward" hermaphrodites – declared males that eventually sport female flowers – as opposed to the usual female-to-male hermaphrodites. These are semi-rare occurrences, usually sterile but sometimes viable, that I have found at times to be valuable in their genetic contributions. Some of the most resinous and desirable males I have encountered exhibited this trait. This trait almost seems to guarantee against unwanted hermaphroditism in subsequent generations as it also increases the female to male ratio in its progeny.
So, it appears that these "freak" plants may, in fact, be potential "jewels" in the breeding process. Reports of highly potent hybrids being created with these "hermie" male plants that sport unusually resinous offspring are being heard of more and more. The breeding potential of these Backwards Hermaphrodites may just be beginning to be understood and certainly merits further exploration.
It is important to be aware of Hermaphrodism so that you will be able to recognize the early warning signals. Removal of these plants is essential to keeping your garden seedless and without genetic imperfection. Unless you come across the exceptionally rare Backwards Hermie, Hermaphroditic plants have no value in your garden.
The topic of sexing your plants need not be so mysterious or intimidating. It's simply a matter of knowing what to look, where to look for it and when. It is our hope that Breedbay's "Ultimate Plant Sexing Guide" has helped you remove much of this mystery and now can serve as a resource you can return to often to answer any questions you may have.
Thanks to all who have allowed us the use of their wonderful photos to help make this tutorial. All content for this guide was obtained through internet searches and compiled here. No copy and paste of any info was done unless credited to the original author. Any photo used that are uncredited have remained so as photo credits were unavailable for these photos.
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