Monday October 28, 2019

By Abby Hutmacher

How to Predetermine the Sex of Cannabis Plants Growing

Female 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


Why Sex Cannabis Plants?

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.

Male/Female Plant Comparison
Female (left) and male (right) cannabis plants in early stages.

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. 

Steps for Sexing Your Cannabis Plants

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.

Because clones are exact genetic copies of their parents, forcing a clone to flower separate from its parent will give you a clue regarding the specific gender of its parent.

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.

Male Plant
Example of a male cannabis plant.

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.

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

Abby Hutmacher Abby Hutmacher



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