Go Back

It’s A Boy!

Pollination, breeding & how to avoid pollen contamination
By Colin Gordon and Ben Owens

For even the most inexperienced growers, the importance of sexing plants is well known; if you’re growing for that sweet sinsemilla, that seedless beautiful flower ripe with cannabinoids, you want to ensure you’ve only got females in your garden. The dreaded male plant is feared by many as a “crop ruiner”. Common advice is to tear up and toss out any males that appear. But, if you’re a breeder, or looking to try your hand at creating your own genetics, a male can be an attractive opportunity for a variety of possibilities. Similarly, if you have a standout female that you’d love to combine with another standout female, reversing one of these plants could allow you to create the desired cross, but what do you do about the pollen? And what type of breeding are you attempting? We dive in to the various types of breeding, the process of pollination, and advice on how to avoid cross contamination and protect your ladies from your male or reversed female.


Breeding is a simple process: you need pollen and pistils. Pollen comes from a male plant or a reversed female whose pollen production has been induced, and you then coat the female plant(s) with pollen. But not all breeders are the same. Those breeding with intention are likely looking for specific traits, while those with less intention may simply be opportunistic with unexpected pollen. At the bottom rung, there’s the unintentional, "oops I found a male too late” breeding that largely produces unstable, intersex-prone genetics. For our purposes, we’ll be talking about intentional pollination, based on an concerted effort to breed a plant with another.

There are three main types of cannabis breeding:

Directional Breeding

One of the two true breeding pursuits, directional breeding looks for a specific trait or cultivar and attempts to hone in and stabilize that particular expression or trait. For example, if you are particularly fond of a specific terpene profile, directional breeding would allow you to narrow your focus with each filial generation, seeking to identify that one particular phenotype that gives that exact terpene profile, regardless of other aspects.

Compensatory Breeding

The second of two true breeding approaches, compensatory breeding attempts to take the best traits from two plants and produce an offspring with a balance that compensates for each of the parent’s shortcomings. For example, if you wanted to tame a gangly, tall strain like a Haze while getting the gassy, bushy nature of a Chem Dog or Afghan Kush, compensatory breeding would be selecting parents whose combination would compensate for each plant’s weaknesses (in this case vertical height and spacing of bud sites).


Not a true breeding type, but something colloquially referred to as “pollen chucking.” This is the least intentional of the three efforts to breed. As the name suggests, this breeding method starts and ends with having pollen and applying (chucking) it on your female plants. You’re intentionally doing it but you may not be selecting pollen or recipient plants for any reason in particular other than that you want to breed something, anything. The goal here is to produce seeds, nothing more. Hopefully they’re great, but the intention is to make something, not necessarily something special.

Many breeders use a combination of Directional and Compensatory Breeding to create their genetics. Then, there are seed-makers, those that have no real end game in mind, who are crossing what they believe to be two worthwhile varieties. ETHOS uses compensatory breeding in our initial projects, then, once particular expressions have been identified and selected, we breed directionally, to homogenize each expression in its truest form.


Once you’ve gotten a male or reversed female that’s producing pollen, you need to get that pollen all over your female plant(s). ETHOS’ first seed batch was a run of seeds done in Colin’s home grow. Around Day 24 of flower, five female plants (about the size that they would have produced a 4-6 ounces of flower) were selected and laid down on the floor. We slapped the branches together three times over the course of two days. A bit overkill in hindsight, but it worked. It also left a dark stain on the wood floors.

This experience, as well as countless breeding projects since, have taught a few lessons, passed down in the process below:

• Acquire pollen from a male or reversed female.

• Identify females to be pollinated.

• Remove all fan leaves from female plants. Your goal is to expose as many pistils as possible. This will allow for the easiest pollination.

• Optional, but advised: Lay a tarp, plastic sheet, or other non-porous covering on the floor to capture excess pollen for disposal or future use. Alternatively, you can put the plant in the tent to help contain the pollen and increase efficacy by losing less to the room.

• Lay female plants to be pollinated on the ground. This will minimize the amount of damage done (you can break the plants if upright in the air, and no control of pollen spread).

• For heavy pollination, brush the plants vigorously with each other; use the pollen donor plant and literally slap branches to branches. You can use the pollen branches like a paint brush, moving them in and out of the plant, through all of the internodes. You want to inundate the pistils with direct and indirect (plumes), physically getting into all of the nooks and crannies of the plant.

• Flip the plants over and repeat Step #5.

• Repeat until the plants, and floor surface, have a visible layer of pollen.

• After three days, you should see the pistil hairs shrink completely down from the strong, white, visible postil, to a red, ripe pistol that has now retracted into the calyx and bracts.

• The last step is to wash the plant once pollination is confirmed. If you plan on moving the pollinated plants back into your main grow, thoroughly wash plants with RO water. This will not only clean the plant of excess pollen that could be transmitted to neighboring plants, but also activates the pollen being inspected by the pistils, triggering a higher fertility (success) rate. If you plan to keep your pollinated plants isolated, you should still spray them down with RO using a spray bottle, but the full wash is not necessary as you aren’t as worried about contamination as you are working to increase fertility. Also, by washing it away, you’re preventing straggler seeds; all seeds will ripen at same time.

Avoiding Cross Contamination: Keeping a Male Cannabis Plant without Pollinating your Females

Once you’ve selected your pollen donor, it’s important to isolate and properly grow the plant out in order to collect pollen without cross contamination, without the risk of pollen reaching your primary grow. You can keep your pollen area completely contained with the help of negative pressure, some carbon filter fans, and a couple of HEPA filters on your outage. The most important part is to prepare for failure by setting up two, autonomous ventilation systems that use HEPA Filters.

HEPA filters remove all pollen, and, while one fan is enough, having two creates an intentional redundancy as a backup plan just in case one breaks. If a fan goes out unexpectedly, the next thing you know your negative pressure is gone and your pollen is leaking out, creating the perfect pollen storm. Below, you’ll find the materials needed and a simple process for setting up a pollen containment area. This setup is large enough for a 400 sq. ft. area (20x20).

What You'll Need:

• 2 6” Adjustable CFM Carbon Filter Fans

• 6” inline fan ducting

• 2 Separate HEPA Filters: Running two filters puts a nice stanky pressure on your grow area.

• VISQUEEN tape for bottom of door and all seals (room or tent)

Creating Your Pollen Room or Tent:

• Isolate a pollen donor (male or reversed female) and an isolated area to grow it in (tent or small room).

• Set up two, standalone exhaust ventilation systems using fans and HEPA Filters. These should use different outlets, ventilation, etc. One is a failsafe for the other; if they’re on the same system, they both fail and your redundancies don’t help.

• Put VISQUEEN tape on all seals and doors to prevent leakage.

• Turn your systems on. The goal is to be creating a negative pressure to where when you open the door, you can feel the pull.

• Make sure to change all filters as directed. If they stop functioning properly, and stop filtering as needed, you may end up with issues.

Playing with pollen can feel like a gamble if your primary grow is in the same building, but, with the right precautions, you can preserve your pollen donors, and create your own breeding projects that remain isolated from your main crops.

For smaller pollination goals, collecting pollen in parchment paper and simply dusting small amounts on flowers once they are out of the main room will work just as well; use the same conditions, and washing routine, even if using less pollen. A teaspoon of pollen is going to have 10s of 1000s, if not 100s of 1000s, of pieces of pollen. Even with small pollination efforts, take all the precautions.

Let’s match.
Search for the strain that suits you.
You’ll know it when you see it.
Flowering Time (Days)
Life Cycle (Days)
Cannabinoid Profile (TAC)
Terpene Profile
Height / Vigor
Internode Length
Ideal Environment
Grow Level