Does Cross-Pollination Change THC Level?

I have a high CBD/low THC strain that I’m going to pollinate with pollen from a plant that is much higher in THC, I’m just wondering if any one knows whether that will adjust the level of the THC of the strain? The level of THC is about 0.5-1% so I’m hoping that will remain the same, any ideas?

1 Like

There will be a change as you are crossing 2 different varieties with different genes. You will have several different phenotypes appear, so you might find some thing that has what you are after thc wise. But as a rule the variety you are using as a pollen donor is higher in thc so I think you will have a slightly raised thc level in the new cross

1 Like

I’m not sure what your interest is with pollinating, whether it be seeds or crossing genetics etc but I did read,

If this is the first time you are pollinating cannabis plants, it is best to avoid experiments. That is, don’t try to create a new strain, or mix them, as this requires painstaking work more appropriate for specialised genetic banks and veteran growers. If you try to, your combination could be successful, but it also may might be a real flop, and you could waste a whole crop by creating genetics that are highly unstable. To avoid an unnecessary fiasco, at least until you get the hang of pollinating cannabis, it is best to select males of the same genetic as your females.

Pollinating 1 bud on 1 plant is the way for you to go. That way you are not loosing all your smokable material to seeds and you can still experiment with your cross and hopefully find a phenotype that suits your requirements. If your cross pollination does not meet your expectations you have only wasted 1 bud on the process. Breed away my friend, you might create something exceptional.


Even using the same species can reveal a recessive trait in that generation that can make your seeds from that plant express different dominant and recessive traits. That could make the product contain more or less THC and CBD @mountainman1 has the right idea, one bud on one plant.

1 Like

I’ve pollinated a whole plant before with success although the seeds take a while to sprout, but this strain came from feminized seeds so I have no males, I have 2 of the same variety (Dinamed) so will pollinate one plant and leave the other, I guess the proof will be in the pudding, what do you mean by unstable genetics? Also anyone know about creating feminized seeds?

If your pollen donor is a pure genetic male plant your resulting seeds will contain both male and female genetics. If the pollen donor is a female that you have applied colloidal silver or such to produce male flowers on a female plant the seeds will be female. Go ahead with your plan to breed and next crop grow out some of the seeds and keep notes on all plants in the batch. Take cuttings of anything that meets your criteria and when the plants have flowered you can sample them and make your selection. Discard all clones that dont meet your standards and take another cutting from the clone you want to keep. Put both the clone and the new clone into flower and apply colloidal silver to 1 clone only until it produces some male flowers. Use the pollen from this plant to pollinate your other clone. Voila female seeds

1 Like

Wow, so if I’ve got 2 females growing of the same strain I could apply colloidal silver to one of them and use that pollen to pollinate the other? (or could it pollinate itself?) then I’m assuming the THC content would remain the same. How do you apply the colloidal silver?

If you allow it to pollinate itself, you risk creating a batch of feminized hermies.

Don’t forget your BASIC plant genetics. Remember those Punnet squares?



It will probably inadvertently pollinate itself anyway if it’s producing pollen whilst flowering but glad you mentioned that, thanks for all the answers people you’ve solved my dilemma!

try and you tube some info on colloidal silver , there is some great info and videos to watch, will help you immensely

1 Like

I think it’s been vastly oversimplified. THC and CBD production are probably controlled by many genes. When you do sexual reproduction instead of four combinations (the product of single gene differences) you may end up with 20 or 30 different phenotypes. You would need to grow each of many plants out to harvest, while keeping a clone mother plant of each for later. Then you have to pay a lab to test every one of those plants to see what you got in terms of THC and CBD production. If you get one you like, you clone more off it’s mother plant.

It’s a huge amount of work and you need a facility where you can grow lots of plants. And it costs a lot of money because most of the plants will not be what you want.


@Donaldj @Majiktoker don’t you guys have some breeding experience to help @poisongodmachine out with this endeavor?

Do you mean that just because I pollinate my strain with pollen from the same strain, it doesn’t necessarily mean the THC level will stay below 1%?

Any time you do sexual reproduction it can change. If you cross it with a male of the same strain, you will get multiple phenotypes. Every plant caries two copies of each gene. A really stable strain will have each gene’s copies the same, but even Northern Lights which has been around for decades has different copies so crosses within the strain result in different phenotypes.

Often a gene has a dominate copy and a recessive copy, and you can’t tell if a plant has DOM-DOM or DOM-REC because the phenotype (the expression of the gene) is the same. You can only tell if it REC-REC because then the phenotype will be the recessive trait. (Unless you do the DNA sequencing, but you have to know the gene you want to look at, which is very very hard to find.)

Your high CBD strain may be such a REC-REC (or a DOM-DOM) for CBD production because that is the only gene the breeder tried to breed for. It gets very complicated when you want to select for multiple genes. If the breeder selected for low THC and high CBD, then two or more genes may be homozygous (the same in both copies) and you are good to go.


Very interesting thanks for the info, this plant is both low THC and high CBD so I’m hoping the seeds will produce the same plant, but as you explained there’s a chance the THC level may increase right? even if the pollen is from the same strain

Possible. Making seeds is kind of a craps shoot. Making clones is simpler and the babies are exactly the same.


It would not be the first time a backyard breeding experiment has unearthed a killer plant.