Sexing
Sexing, or determining the gender of your cannabis plants is an essential process. While they can sometimes exhibit hermaphroditic traits, with both female pistils and male stamens, they are typically either entirely male or female.
Around four or five weeks into the growth cycle, you’ll have the opportunity to sex your plants. Although it’s often considered a challenging aspect of cannabis cultivation, marijuana sexing becomes easier with experience. The purpose of sexing your plants is to identify and remove male plants before they have a chance to pollinate the females. Pollination leads to seed development, diverting energy away from THC production, which is undesirable. Around 4-6 weeks into growth, pre-flowers begin to appear, indicating the right time to eliminate the male plants and initiate the flowering stage.
Cannabis is a dioecious plant, meaning that males produce pollen and females produce seeds. However, hermaphrodites can occur, as is the case with various other forms of life. Unless you’re breeding or cultivating for seed production, it’s preferable to have all-female plants. Unfertilised calyxes or buds are the most potent and psychoactive part of the plant, containing THC, CBN, and CBD. Seedless buds, known as sinsemilla, are highly sought after for smoking, as they haven’t allocated energy or weight to seed production. Therefore, dedicating resources, time, and space to male plants is wasteful. Early identification and segregation or removal of male plants before they release pollen are crucial.
While pre-flowers may sometimes appear during the vegetative stage, they typically require the transition to the flowering phase, which involves shortening the light regimen to 12 hours of light and 12 hours of total darkness.
Flowering is the only true way to sex your plants
Although you may get a clue from their growth patterns before flowering. Male cannabis plants tend to be leggier than female plants with a longer inter-nodal length.
Female plants are squatter with more leaves and a bushier aspect. Male pre-flowers should be clearly visible to the eye, although a magnifying glass will make your job easier.
Male flowers form at the junctions of the branches and stem and the pollen sacs form little balls.
Female pre-flowers will also form at the junction of branches and stem but will normally start to form at the fourth or fifth branches up from the base.
They are easily distinguished by the appearance of pairs of tiny white hairs, known as pistils.
Some growers force flowering by changing the light cycle before the appearance of pre-flowers. They then watch their plants closely for the appearance of flowers and remove the males. However, others believe that this can stress the plants and is not a proven way of speeding up the process as plants forced in this way may spend longer in the flowering phase, cancelling out the advantage.
Identifying gender
A magnifying glass is helpful though not necessary. Look near the top branches right where they fork from the stalk.
The male sex organ will look like a small playing card-type club. The female sex organ will display a calyx with two small white hairs protruding from the top.
If you are unsure or unable to determining the sex, then simply wait a few more days until the organs are more mature and easier to identify. The males are still way too young to create pollen so there is no danger in waiting.
Chemical Leaf Tests
Chemical Leaf Tests Can Determine Sex & Potency for plants as young as 1-3 weeks and is getting less expensive every day. It can be used on cannabis seedlings with just a few sets of leaves to test for sex and future potency.
These tests only require a tiny amount of plant tissue (for example a small punch-out from a leaf, or a single cotyledon leaf), so it won’t hurt or slow down your seedlings to take a test sample!
In general, the tests are available for seedlings as young as 1-3 weeks. Sex testing uses a real-time polymerase chain reaction (qPCR) test, and potency tests use Gas Chromatography with a Flame Ionisation Detector (GC/FID) or High-Pressure Liquid Chromatography with a Diode Array Detector (HPLC) for testing.
Although testing can be done as early as week 1 from germination, waiting until week 3 to conduct testing on seedlings can increase accuracy, and some companies won’t conduct testing until week 3.
There are many reasons growers would like to know plant sex as early as possible, as well as be able to estimate the overall THC/CBD ratios of future buds!