Time is money – the advantages of early sex determination in Cannabis through PCR tests

Why is early sex determination crucial in the Cannabis business?

Only unpollinated Cannabis female plants produce flowers rich in cannabinoids. To avoid unwanted pollination, most growers will discard male plants as soon as they’re able to identify them, unless they are needed for breeding purposes.

The take home message is that, if you’re a grower, a breeder, or both, you need to know the sex of the plants ASAP to optimize your crop yield and/or plan crosses to increase your business.

This blog discusses methods for early sex identification of Cannabis plants, focusing mainly on the advantages of early sex screening using PCR (polymerase chain reaction).

Comparing methods for identifying sex in Cannabis plants:

Not only do male and female Cannabis plants look different, but they’re also different in their DNA. Because sex is genetically determined, male plants have DNA sequences that females don’t carry, and these sequences can be detected even before plants grow to look like males. Next to visual inspection, PCR is the most common method for determining Cannabis sex at genetic level.

Visual Inspection:

  • You can identify Cannabis plants’ sex by looking at their physical characteristics once the plants are fully developed (around week 6) or when the plants are in the pre-flowering stage (around week 4). 
  • Male preflowers typically develop small, sac-like structures called pollen sacs, while female preflowers exhibit hair-like pistils, which eventually develop into flowers.
  • This method requires specialized personnel to perform careful and frequent observations.
  • The main disadvantages of visual inspection is that it is both laborious and time consuming, strongly  impacting production costs by affecting personnel cost, canopy space, and resources cost.


  • PCR accurately determines the sex of Cannabis plants by specifically detecting genetic material carried only in the male Y chromosome (DNA). 
  • Early sex screening allows growers to remove male plants from the cultivation process in approximately 2 weeks after germination, saving valuable time, space, and resources. 
  • Historically, PCR was performed only in specialized labs. Through miniPCR Dx , PCR is now available and affordable to everyone. Y-spotter™Cannabis DNA Sex Test can be carried out by minimally trained personnel, with easy-to-use equipment. The tests take less than 90 minutes, with less than 30 minutes of hands-on work. Results are easy to interpret: green fluorescence indicates male plants.

Let’s do the math

The cost of growing a Cannabis plant depends on various factors such as location, cultivation method, genetics, and individual preferences. However, $18 per week per plant is a rough estimate of the costs involved. 

  • Identifying a male plant when it is 2 weeks old instead of 4 weeks old will save about $36 per plant! Plus, you will have more space for starting the growth of new plants, increasing your yield.
  • The cost of an early sex test is marginal in comparison to the growth cost, with our Y-spotter Cannabis DNA Sex test running approximately $4.00-$4.50 per test. The purchase of the equipment for in-house testing requires a small initial investment, but it is quickly amortized.
  • Shipping the sample to an outsourced lab generally costs about $15 per test.
  • In-house testing provides you with immediate results, instead of waiting for shipment time and test results from an outsourced lab.

Table showing an example of the estimated expenses for growing 100 plants based on the different sex determination approaches.

*$5,085 refers to the first round of testing and includes the equipment expenses. Once the equipment cost is quickly amortized, the total cost will be only $4,025.

Conclusion: unwanted males will cost you time and money

Male Cannabis plants are mainly used for breeding. If breeding is not your goal, you’re better off eliminating male plants early to prevent unwanted pollination and to save space in your grow. Not too long ago Cannabis growers had to wait many weeks to determine plant sex, but PCR testing now allows you to identify males as young as 14 days. PCR-based sex determination allows growers to focus their time and resources on valuable female plants, resulting in cost savings and higher profitability. In-house Cannabis sex testing is now a reality, offering convenience and time efficiency over costly and time-consuming third-party testing. 

Related resources