Micro-breeding: Auto- hemp population development

I am posting a side project into the feasibility of “microbreeding,” with (relatively) large populations of plants, during which I am playing with the development of a heterogeneous autoflowering hemp population on a micro (2x4 grow tent) scale.

Cycle 1: initial cross
I began with 18 CBD-1 females (autoflowering, CBD dominant (type 3) plant) crossed to 3 males (photoperiod, THC dominant (type 1) plants):
-THSeeds Heavy Duty Fruity (true male)
-DNA genetics Golden Lemons x unknown male (true male)
-Grandaddy Purple Candyland reversed female clone

Cycle 2: F2 seed production
I then grew out (to completion) this F1 seed in 4, 72 cell trays(288 seeds) and switched to 12/12 at week 2 from emergence. Plants were allowed to open pollinate with natural males present. Seed was retained separately from individual female plants.

Cycle 3: Selection for autoflower
F2 seed was grown in 4, 72 cell trays again (288 seeds planted), representing 6 seeds from each of 48 female lines from cycle 2 (48 of the 288 cycle 2 seeds planted were females that made seed). the light cycle was left as 18/6 throughout. Photoperiod plants were culled. Autoflowering plants were again allowed to open pollinate with natural males. Seed was retained separately from each female plant.

Cycle 4: CURRENT CYCLE; feminization of population
F3 seed is currently being grown out in 4, 72 cell trays again. 288 seeds were planted, representing 2 to 30 seeds from each of 21 F2 plants (21 of 288 F2 seeds planted were autoflowering females that produced seed). Males are rouged upon sexing. Once all plants are sexed and only females remain, all will be reveresed and allowed to open pollinate.

Cycle 5: FUTURE. No longer micro?
A few hundred F4 seed will be grown in a greenhouse in 1 to 3 gallon pots and resulting plants tested for CBD/THC content. At this point all plants should be autoflowering, but will hopefully be segregating for THC and CBD content. High CBD plants will be selected for selfing and all others destroyed.

Cycle 6: FUTURE
S1 seed (from selfed F4 plants) can be grown out and evaluated for superior lines.


Interesting project, good luck to you.


Right on, I’m down for the show. Best of luck to your endeavors


Thinned out males and some plants that were extreme stragglers. Some root rot deaths among females.

Fairly unequal conversion. I split them among 2 different treatments; one worked better. Good seed set.


Cool project! You made a good plan and are executing it nicely. I’ll be interested in how it progresses.


Wow. That makes growing in solo cups look like they have room to run around.
Impressive growth, being in only about 1.5oz of soil each!


Very cool. I’d like to follow along.


I cut them all a week ago. All seeds were bulked, except one F3 female family with three plants that were kept separate and a single other plant. The 3 plants from the same F3 female had a candyland bud structure and good scent. The other one I kept separate was selected solely for density. The candyland family was heavily reversed and at least some seed is probably S1 already. The Density plant had no male flowers so all seed is half-sib.

Over all there were 54 plants from 12 F3 female families represented with 1 to 14 plants from each with random pollination (1,2,2,3,3,3,3,3,6,7,10,14). Seed yield is 14.8 grams; looks like ~1000+ seeds or so.


Very nice plan and thanks for keeping this up to date

As for the strains below you have crossed each of these with the CBD

So is the out come to have high cbd low thc varients of these strains or 1:1 or 2:1 , 3:1 etc… or just see how they sturn out and go from there?

They sound like some interesting CBD strains and the bonus is auto.


The goal is to pull out some 20+:1 CBD:THC autoflower hemp lines that are just something new. They had a few generations to shuffle before this one, where they will be sorted for chemotype and selfed.

This is sort of a hobby breeding project that I wasn’t sure would work in the 72 cell trays. If I were to do it again, I would reverse a group of the original CBD1 auto to a large number of elite photo period clones and elite seed lines, then take it out to F3 or F4 the same way before selfing. The idea being, take some diverse elite lines, let them intermix with an early auto hemp variety, then sort for new, recombinant, multilocus genotypes that are auto hemp (an underdeveloped category).


I’ll have to read that again and soack it up but sounds good :thumbsup:

i’d like to see more of the elite seed lines in cbd auto

No it doesn’t. Federal law just says it needs to be under 0.3 delta-9-THC. The USDA has set the rule as 0.3 total THC 15 days prior to harvest. Nothing in the law says anything about the variety being historically hemp or marijuana derived, as “hemp” is a legal term and is essentially meaningless botanically. Nearly all modern CBD cultivars are drug-strain derived, rather than derived from traditional hemp food seed or fiber varieties.

I’d like to see where Ed said such things. I am betting he may have been talking about CBD itself only being legal when grown from plants grown legally as hemp, rather than CBD derived from marijuana (this was referred to as the “source rule” when used to defend the legality of hemp derived CBD as an exception from the controlled substance act after the 2014 farm bill legalized it but before it was officially descheduled in the 2018 Farm Bill).

P.S. Hemp is Cannabis.


Cycle 5:


@GrowingHigher You were vegging and flowering in the 72 cell trays? That’s really micro. I’m impressed.


Yup, essentially 12/12 straight from seed.


Cool project. Just curious how’s heavy duty fruity? I read so much good stuff about it years ago and always wanted to try it.


I honestly don’t remember. My roomate at the time was growing it and those just happened to be the males I had around at the time.


I’d like to see more of the elite lines bred with CBD. Gives those that like or can only use with CBD options to try the elite lines too. :thumbsup:

I’m going to watch this one closely thanks @GrowingHigher

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Cycle 5:
Screened for ratio, 16 were putatively identified as type 3 (hemp) plants:

And the doomed rejects:

If anyone wants some seed of this generation to tool around with, I would love to share. It should all be female and autoflowering, but is segregating for THC:CBD ratios. I have plenty left, and probably won’t go back to it after this. DM me if you want to play.


Any gonna still have high thc at this point?

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