How to Sex Cannabis Plants

When growing Cannabis the end goal is to produce a plant that is female and will produce flowers. Cannabis is a phototropic plant meaning that it responds to lighting cycles ranging from long summer days to short winter nights.

This video shows Phototropism in action.

Having the ability to identify if the plant or plants you are growing are male or female, will allow you to flower only buds without the risk of an open pollination occurring between a male progenitor and the female plants.

Below I explain how to identify male and females, the window to do so, hermaphrodites, as well as the advantages of regular and feminized cannabis seeds.

How Long Before I Can Sex a Cannabis Plant?

After a seed has successfully sprouted into a healthy seedling, growing under a lighting regime of 18 hours light and 6 hours dark the plants will grow into a vegetative state.

After five to six weeks of growing the plants will begin to exhibit pre-flowers, which are the very first signs of the sex of the plant. Naturally the male plants will display pre-flowering characteristics earlier on than females due to the way the males must synchronise in nature when pollinating.

If you are flowering seedlings immediately under a 12/12 light cycle, then the plants will still take around three to four weeks to reveal any pre-flowers. Either way there is no real concern when growing plants in the vegetative stage for unwanted cross pollination from unidentified male plants and the male and female pre-flowers will be easy to identify.

What Are the Identifiers of a Male and Female Plant?

A great tip here is to use a magnifier glass, lupe or even a good camera phone and to get as close to the pre-flower as possible. The pre-flowers will appear at the internodal spacing and in between the fan leaf and the axillary shoots.

Upon first glance they may be difficult to see, however, once you have spotted them there will be one of two things to see. A female pre-flower will reveal its first pistil which is the white hair that grows around the calyx of the flower. Often challenging to identify, yet this tiny white hair is enough to show the plant its sex early on to a well trained eye.

The white pistils of the female flower
The white pistils of the female flower

On the other hand, a male pre-flower will appear to be a cluster of small ball shaped sacs, or at least look like an oval shaped tip. As male plants begin to pre-flower heavily, the cluster of oval shaped sacs will become more prevalent and easier to see. Sometimes plants can reveal both male and female pre-flowers indicating the plant growing has hermaphrodite traits.

Hermaphrodites

A plant that has become a hermaphrodite

There can be a number of reasons why a Cannabis plant can show characteristics of hermaphroditism. These factors may be genetically engineered, environment based, or generally stress induced.

A hermaphrodite is a plant with both male and female flowers which ultimately leads to a plant that pollinates itself and any other surrounding plants causing a seeded crop and waste of time and effort.

Identifying a hermaphrodite is not always easy as some plants will begin to hermie later than others due to stress such as big shifts in daytime and night time temperatures, excessive heat and uncontrollable humidity, physical trauma such as a power cut leading to a fluctuation in the light cycle, brief shutdowns of hydroponic systems, or a break or snapping of a branch in flower.

It is important to know that pollen from hermaphrodite plants will not produce reliable seedlings and the offspring will only display the same characteristics.

Once identified, hermaphrodite plants should be removed from the grow room and safely disposed of well away from your other plants. To spot a plant with both male and female flowers should be easier. The plants begin to enter the later stages of the flowering period and some may appear as a single pod of pollen emerging from the tops of the calyxes.

Regular and Feminized Seeds Explained

Through breeding and stabilizing original strains and hybrids, the diversity of Cannabis genetics has evolved to new heights and are backed by a thriving market place both commercially and medicinally.

Old school growers will testify that the only type of Cannabis seeds available before 2000 were regular seeds. There was no such thing as feminized seeds as yet. Regular seeds mean that a grower is required to sex their plants and remove males, unless their intention was to breed with a male and female plant.

The advantages of using regular seeds were that from the females grown out, you would have a high number of desired traits appearing in the different phenotypes and from a breeding stand point, the stability factor would have been far more stable in terms of hybrid vigour.

The only downside to using regular seeds was that if you were not already working with female clones previously taken from regular seeds, the risk of losing plant count once flowering commenced could reduce anywhere up to 50% or more. Meaning that running organic or  hydroponic systems would be inefficient and a waste of vital space.

Feminized seeds were first created in Holland back in 1998 with the intention to produce a plant that was all female and that could withstand the challenging cold and wet weather associated with Northern Europe. By treating the plants with Colloidal Silver, the farmers were able to grow an entire crop of all female Cannabis plants, that showed no hermaphrodite traits at all.

After 1998

After 1998 it was not long before feminized seeds revolutionized the seed world and since then the popularity for female seeds massively dominates the European market place. The benefits of using feminized seeds are that every plant will grow to be female meaning all of the grow space is fully utilised, plant training can be practised earlier on and the most important thing is nutrients, growing medium and time spent is not wasted.

About Stoney Tark

imageStoney Tark is head writer for Soft Secrets, High Times Magazine and Weed World. He is also the main breeder and owner of Prana Medical Seeds.

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