Your First Cannabis Cross: Isolate the Male, Then Brush, Spray or Bag the Pollen

How do you make a cannabis cross?

To make a cannabis cross, you isolate a good male, collect a little of his pollen and apply it to just one or two buds on a female that's in full flower, with at least a month left before harvest. The seeds take about six to seven weeks to finish, and the rest of the plant keeps making normal, seedless bud. Plenty of growers figured home crossing was a myth; it isn't, it's mostly a matter of timing.

The sweet spot is when your plants are in full bloom but there's still more than a month to go before harvest on the earliest-finishing strains. That's the moment, if you've got a male on hand or know someone who can hook you up with some pollen.

Hybrids, the result of crossing two cannabis strains, are new strains with their own personality: new flavors, different effects and different plant structures. The best part is that the end result can be all over the map, and some of those surprises taste amazing.

Modern hybrids come out of a long, grinding process of breeding and selection, all aimed at a new strain with different or improved traits. In other words, they're made with one goal: boosting the qualities we love in cannabis, whether that's flavor, effect, duration, how well it adapts to its environment, life cycle or anything else.

Most growers only want females so they get a seedless crop, because any male in the grow, or even nearby, can send pollen flying and fertilize some or all of the female flowers. The result is a not-so-great surprise: seeds in your buds.

Smoking seeded flower is no fun. Seeds are easy to pick out when you can see them, but if you miss them and they go through the grinder, the result is nasty: the seed hulls leave a horrible taste and can ruin what should've been a delicious bud.

So step one is spotting males early and pulling them, unless you actually want some seeds for your next grow. If that's the plan, here's how to do it without the whole garden paying for it.

How to prep for a cannabis cross

First things first: once you've got at least one plant of each sex, isolate the male. Male flowers develop fast and within a few days they open and dump all their pollen, which is exactly what you don't want. To get a handful of seeds, pollinating one or two buds is plenty.

Pick the best male you've got. Males usually flower and show pre-flowers sooner than females. That's nature's timing: when the male flowers mature and the sepals open, releasing the pollen held in the stamens, the female flowers should be in full bloom with plenty of calyxes ready to receive it.

Naturally, that happens from around the third or fourth week of the females' flowering. Since you don't want the male spreading pollen all over the garden, move him into a closed space, inside your house or somewhere else, behind a window and without much airflow. The lighting doesn't matter much at this point, because the flowers will keep developing. As soon as you've collected some pollen, you can say goodbye to the male: cut him down, seal him in a plastic bag and toss it in the trash.

Sometimes the male gets ahead of the females, and they haven't hit weeks 3 or 4 of flowering yet or don't have decent-sized buds. The fix can be a light trim on the male: remove the most advanced flowers that are about to open, and always leave a few that are halfway there.

Let's get started: collecting pollen and four ways to apply it

Pollen stays good for about 3 to 4 days after you take it from the male flowers, then it starts losing fertility. You can also freeze it, and the upside of doing that

is that it lasts a bit longer, and letting it thaw at room temperature is enough to make it fully viable for crossing.

Collecting pollen is pretty easy, all things considered: as soon as you see an open flower, hold a small jar underneath and tap it so it drops a fine yellow dust. Another option is to pick a few unopened flowers and leave them somewhere dry; in 24 to 48 hours they'll have opened, and a few taps will shake the pollen loose.

The cool thing about this stage is that there are several ways to pollinate, and they all work just as well, so go with whichever feels easiest. Here's a quick rundown:

Paintbrush: collect the pollen in a jar. If you can, cover the whole plant with a plastic bag, leaving out one lower branch, which is the one you'll use. Carefully load the brush with pollen, then brush it over the bud and give it a little shake.

Spray: mix the pollen you collected with distilled water and pour it into a small spray bottle. Same as before, cover the plant, leaving one branch outside, and mist it until the whole bud is soaked.

Bag: put the pollen in a bag (a zip-top bag is best because it's easy to seal), carefully slip one bud inside, close the bag snugly around the branch and shake it gently so the pollen coats the bud.

Natural pollination: for this one you need a few small, late female clones, around 30 to 40 cm (12 to 16 in) tall, that you pollinate whole. Keep them indoors right next to the male for a few days and let nature do its thing.

If you need to cover the plant, do it during the cool hours of the day, because it'll have to stay covered for a few hours. Then give the pollinated bud a shower with a water spray to wash off leftover pollen. And don't forget to mark that bud with a tag, or whatever works for you, so you don't mix it up.

How do you know your cannabis cross worked?

It won't be long before the stigmas (pistils, or little white hairs, whatever you want to call them) start to wilt and dry out. They'll begin to lose that classic white color everyone knows, the way they look late in flowering. That's the unmistakable sign you nailed it.

From there, the calyxes start developing seeds inside. They swell up and show a seam running lengthwise along the top, which splits open to show the seed once it reaches full size.

Seeds need roughly six or seven weeks to fully form. A plant meant for seeds also has slightly different nutritional needs than one meant for buds: on one hand, seeds call for high amounts of nitrogen; on the other, buds call for phosphorus and potassium.

In principle, a regular bloom fertilizer will do the job, although if you're pollinating a small plant or a whole clone, it's worth keeping this in mind for better-quality seeds.

Sometimes the seeds haven't turned their typical dark color yet but the buds are ready to harvest. In that case you can harvest the plant in sections and leave the branch with the pollinated bud or buds for another week or two. Just keep a close eye on rain and excess humidity.

Dry the seeded buds like you normally would, but put something underneath in case seeds drop during drying. Pro tip: a cardboard box works great for this.

Last step: getting the seeds out of the buds, which can take a while. Put them in a small box and store them like any other seeds, somewhere cool and dry.

After five or six months, you'll find they're in perfect shape to germinate. Even so, it's always better to give them a little curing time.

As for what's left of the buds, loaded with resin, it's perfect for a dry sift with a hash shaker, or you can smoke it as is. Just be extra careful when grinding, because a stray seed might still be hiding in there.

How does cannabis pollination work?

To pollinate cannabis, you need both a female and a male plant. Pollination means fertilizing the female flowers so they make seeds. If you want to keep a female from making seeds, get the males out of the grow area to avoid unwanted pollination.

To pollinate, you put pollen from the male plant onto the female's buds during flowering. The usual advice is to wait until the female is at least 4 to 6 weeks old and in flower before pollinating her, for the best results.

In Argentina, as anywhere, there are plenty of cannabis strains with different genetic traits, including hybrids made by combining different strains. Read up on each strain's traits and pick the best fit for the kind of grow you want to run. It's also possible to reverse a female plant's sex with specific techniques, like colloidal silver, so it makes pollen and you get feminized seeds.

As you can see, it can be a long process, but the payoff is worth it for smokers and growers alike. We say go for it, because who doesn't love experimenting with the fine art of growing cannabis?