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how to sex plants

How to sex plants

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!

For those who’ve never seen a male cannabis plant in its full glory 🙂
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 Ionization Detector (GC/FID) or High-Pressure Liquid Chromatography with a Diode Array Detector (HPLC) for testing.

A single male pre-flower appears
Here’s a picture that shows a pistil right as it’s emerging from the calyx!
Male pre-flowers tend to have a “spade” shape, like the spades from a deck of playing cards. Male cannabis plants often (but not always) reveal their sex sooner than female plants.
Here’s another male pollen sac pre-flower that’s on a little “stem”
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!

Even if you’re not 100% sure about every plant from looking at the pre-flowers, it’s nice to know which plants you need to watch closely and which are definitely female. However, if precision is very important…

Learn how to find tiny pre-flowers at the base of each leaf to determine the sex of your plant in the vegetative stage (at only 3-6 weeks from germination)!

How to sex plants

F emale cannabis plants are the only ones that produce flowers. Male cannabis plants produce pollen which, if exposed to female cannabis plants, will result in seedy weed. Therefore, to cultivate seedless cannabis buds (a.k.a. “sinsemilla”), you must remove all males from a grow environment before pollen sacks form. To do so, you must determine a plant’s sex before they transition from veg to flower. Though most cloned cannabis plants will be female, cannabis grown from seed could be either/or (unless growing feminized seeds, that is). Today, we’ll explain how to determine the sex of your cannabis plants before they have a chance to either pollinate or become pollinated.

As mentioned, male cannabis plants produce pollen which can easily spread throughout a grow area. In fact, a single male plant can pollinate hundreds of females within a single grow space! To make matters worse, male cannabis plants develop pollen sacks before females begin producing buds. It often takes around one to two weeks for male plants to begin producing pollen sacks (characterized by a small “sack” as opposed to a white “hair” or pistil) whereas female plants often take two to four weeks or longer to show gender.
There is an easier way to determine the sex of cannabis plants than to simply watch, wait, and hope it’s not too late. Specifically, you can “force sex” a plant to determine its gender before flowering the whole thing. To force sex a cannabis plant, simply place its clone in a 12/12 light cycle (12 hours of light/12 hours of complete darkness). This photoperiod manipulation signals to the plant that it is time to start flowering whether the plant already has roots or not.

If a clone produces pollen, you know its parent is a male. Conversely, if the clone begins to flower (look for those pistils), you know its parent is female. Now you can remove all male parents leaving only the females behind to flower. No pollen, no seeds, only happy girls and bountiful buds.
Other things to look out for which may help you determine the sex of your cannabis plant include the plant’s height (males tend to be taller than females though much of this depends on the strain type, as well) and the size of the calyx, or the center-most part of a flower. If the calyx is large with a protruding white hair, it is likely female. On the other hand, if small and swollen with no hair, it’s likely a male. This distinction can be made before the plant begins flowering during a stage called “pre-flower.” However, it can be difficult for the naked eye to determine gender at this stage; a jeweler’s magnifying glass can help, though.
Experienced cannabis growers understand the importance of separating male from female cannabis plants. With a little practice, many can catch and dispose of males long before they have the chance to pollinate females. Fortunately, even if you’re just starting the homegrown cultivation process, you can sex your plants before it’s too late, as well. Use these tips to predetermine the sex of your cannabis plants so that your girls will thrive unadulterated.
Monday October 28, 2019
Though genetically speaking, this is a great way for plants to ensure reproduction, modern grow techniques advise against this. After all, once a male cannabis plant drops pollen, any nearby females will produce seeds in response. This not only increases weight, but it also reduces potency and adds one extra step to the smoking process.

Do you have tips for determining the sex of your cannabis plants? Share them in the comments below!

Knowing if a cannabis plant is male or female is an important aspect of marijuana cultivation. Find out how to tell the sex of a cannabis plant in early stages, as well as the benefits of sexing your cannabis plants as soon as possible.