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how many seeds from a polinated cannabis plant

How The Pollen Wars Are Hurting The Cannabis Industry

While medical marijuana and hemp are both varieties of cannabis, the way these plants reproduce can make vast differences in the type, potency, and quantities of the chemicals they express. As medical marijuana and hemp farms increase in size and presence, a resultant war is heating up in the very air around them.

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Let me explain. When hemp and cannabis cross-pollinate, the quality of each diminishes: Cannabinoid potency in cannabis females can reduce, while THC in hemp can increase. This is a recipe for disaster. Cross-pollination ruins crops and costs untold financial damage.

How pollinations works

Cannabis transmits its DNA sexually through the act of pollination. Males develop loose flower clusters that begin as pods. The pods swell and fill with pollen. When the male is mature, and its pods are ready, the pods burst open, spraying pollen from its anthers. That pollen carries on the air seeking to fulfill its genetic mandate of fertilizing as many females as possible. Pollination occurs when pollen reaches the female, triggering female plants to produce seeds.

Cannabis can be both monoecious (plants that can be both sexes, hermaphrodites) and dioecious (plants that have distinct female and male). Both types of cannabis exist in nature, although hermaphrodites mostly only happen when the cannabis plant gets stressed. If a female cannabis plant senses impending death, it will begin to express male characteristics to auto-pollinate.

How it’s destructive.

A 1998 study found that pollination decreased the yield of essential oils in cannabis flowers by 56 percent. While allowing en masse pollination produces a lot of seeds, the resultant buds suffer diminished medicinal value. When plants invest energy in seed production, they make less CBD. If you are a non-medical commercial hemp or seed producer, this may be exactly the sort of outcome you seek from your crop. But mass pollination is anathema to the medicinal producer.

Fathers, lock up your daughters.

In the 1970s, marijuana growers found the longer female plants go unpollinated, the more flowers they produce and the larger they get. This revelation began the modern industrial practice of selecting out males and positive-female selection through clonal propagation or sowing of feminized seed. In a very real sense, the preservation of cannabis female virginity translates to actual dollars. Hence most modern marijuana is seedless sinsemilla, while seeded crops are regarded as inferior.

Combatting the problem

Pollen’s increasing prevalence has caused cannabis producers to ruminate on such topics as its transport on the wind and related impacts of wind speed, direction, precipitation, humidity, topography, and physical barriers.

The ability to isolate growing fields is one strategy used to mitigate undesired pollination. But geographic isolation is apt to prove decreasingly effective as more pollen enters the atmosphere. There may be little to be done, as pollen can travel for miles, and in the right circumstances, it can even be picked up by the jet stream and travel the world.

In late 2019, the USDA funded a $500,000 study on pollen drift. Certain municipalities have also tried to get ahead of the problem through the enactment of isolation ordinances. For example, in August 2018, the city of Snowflake, Arizona passed an isolation ordinance to protect a large marijuana grow operated by Copperstate Farms. Many states also have crop registries so that locations and distances can be identified and maintained. But often data is voluntary and resultingly inaccurate.

Besides physical distance, other mitigation methods are also used—such as misting water between crops to knock pollen out of the air, strategic windbreaks, border crops, or rings of trees. However, physical isolation is best accomplished indoors with air filtration systems. Yet for all its gains, indoor isolation dramatically increases the cost of cannabis production and makes the operation substantially more electricity-dependent. Given the enormity of scale, indoor grain or fiber hemp cultivation is simply not reasonable.

What to do?

If you are a cultivator, your failure to give consideration to pollen mitigation is tantamount to malpractice. If you are scouting cultivation sites, you must consider the neighborhood in terms of tens of miles of radii. Consider, too, the future. As home growers in recreational marijuana states flood their suburban atmospheres with pollen from their porch “hobbies.” (Prepare for disappointment, home growers, for you are filling your air with the very means of your future gardens’ undoing.) If you are an investor, ask to see a pollen mitigation plan before you invest. Don’t see one? Walk. A single crop loss can cost tens of millions of dollars.

SSNO Part 2: Which Plants Are Best for Seed Saving?

This is part 2 of the Seed Saving Nerd Out, SSNO for short. Part 1 last week was a long description of plant reproduction to help you understand which plants you should and shouldn’t save seed from. This week is similar information, organized in a chart for easy reference.

Heirloom tomatoes are one of the easiest and most reliable veggies to save seed from. See the chart below for why.
Should you save seed from a particular plant?

I’m all for experimenting. I love to root an avocado pit, or collect seeds from unknown varieties just to see what happens, BUT . . .

If you want reliable crops year after year, follow the chart below to make sure the plants and seed you invest with your time and energy produce what you expect.

(Scroll down for detailed definitions of each category in the chart.)

Any plant whose flowers generally pollinate themselves before opening. Common examples in the veggie garden:

  • Tomatoes
  • Beans
  • Peas
  • Peppers
  • Lettuce
  • Eggplant

Any plant that requires wind to pollinate. Edible examples are:

  • Corn (and all other cereal grains like wheat, oats and barley)
  • Beets
  • Chard
  • Spinach

These plants either require insects flying between flowers to set seed/fruit or are a combination of self-pollinating and insect-pollinated. For seed-saving purposes, you should assume that insects will cross-fertilize (creating impure seed) unless isolated. Some examples that are likely in your garden:

  • Squashes
  • Melons
  • Cucumbers
  • Broccoli
  • Kale
  • Cabbage
  • Carrots
  • Apples and Pears
  • Almonds

The next three categories refer to how the parent plant came to be. (Lots more detail in last week’s post.)


These are plants that breed true from seed, meaning that seed saved from an open pollinated variety will reliably produce offspring extremely similar to their parents. If you save seed from an open-pollinated tomato, next year’s crop will be the same as this year’s.

This category includes all heirlooms grown from seed (though not grafted heirloom fruit trees — see below). All seed packets will say if a variety is open pollinated or not, and a quick internet search for the variety name will also tell you.

Because we feel it’s extremely important to be able to save seed, we only sell open-pollinated varieties.

Hybrid, or F1 Hybrid, or simply F1

Hybrids are like mules: A cross between 2 different parents (a donkey and a horse, in the case of the mule) creates desirable offspring that either can’t reproduce, or reproduces poorly. “Hybrid vigor” is a real phenomenon, and one of the reasons that so many popular veggies are hybrids. But saving seed from hybrids is always disappointing because next year’s crop will be nothing like this year’s.

Seed packets will always be labeled to let you know if seed is hybrid or not, and if you know the variety name, it’s easy to look up.

There is nothing dangerous or controversial about hybrids, except that you have to buy new seed every year, and are dependent on the seed company.

Grafting / Cloning

All fruit trees are clones, where any named variety is genetically identical to all other trees with the same name. While most require insects to pollinate them and produce fruit, the seeds that result will give you quite different fruit from the parents. It’s best not to save seed from grafted trees.

The cannabis industry also relies heavily on named clones. Most dispensaries have a plant section, where all the plants were grown as clones from cuttings from a mother plant rather than seed. And because cannabis plants are either male or female, and only the females produce the crop of flowers, all the cloned seedlings are female too, and won’t produce seed unless grown alongside a male plant. (I’m not a cannabis grower, btw, but I find the botany fascinating.)

Many popular herbs are also generally grown as clones from cuttings, lavender and peppermint being the most common. Both will produce seed, and the offspring can be quite lovely, but they will be different from their parents. I have lots of self-seeded lavender in my garden, and I quite like how each one is different, but that might not be what you’re after. Again, a quick internet search will tell you if your variety is a clone, or grown from seed. If in doubt, you can always regenerate your herbs from cuttings.