Jack's 3-2-1 Question

I’m in my 2nd week of flower with WW. I’ve been using Jack’s 3-2-1 nutes for the entire grow with a CalMag watering once every week. Now that I’m in the flowering stage should I change anything to produce the best bud I can?

I believe Jacks offers a bloom booster which is mandatory but could help a bit.

Also I believe Jacks has calcium in part b and mag in epsom. Is there a reason ur supplementing calmag? I mean its not a bad idea but u should have a decent amount feeding regularly


Agree with @PurpNGold74 on the flower booster and calcium and mag that’s in jacks. Would also say the flower booster is used the first 3 weeks of flower using a reduced jacks with MPK then it’s back to full jacks :love_you_gesture:

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I switch to 4 - 2 - 1.2 (grams, respectively) to ease up on nitrogen and up the PK, when flowering starts. Did it in coco, no issues. Am doing it in soil (FFOF) and actually just started feeding 5.5 - 2.6 - 1.4 (that ratio brings my tap to 6.38 and roughly 1200ppm) just to see how they do. Girls in later flower (week 4+) are a teeny bit sensitive, but the ones under 3 weeks are actually doing great.


It was suggested earlier when I was going thru a nute issue and has produced very good results while I’ve been using it.

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Part B is 15% N and 18% Ca.
Part A has 6% Mg

Just as a reference when your adding supplemental Calmag… see a Nutrient Antagonist chart (google) to understand what happens (what gets locked out) when there is excess of either.


I’m a little confused. My mix ASPER Jack’s is lower in grams to gal to what you posted.

Add a tablespoon of molasses once a week to your gallons ( assuming your medium has some bacteria) it helps give extra micros and cal mag to help with the flower feedings( i also increase part a with flower time) also dont forget to increase ph to shift from nitrogen focused absorption to phosphorus ( for coco thats 6.2)

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That’s my flower PH for Coco :love_you_gesture:

I think you are seeing everyone has a tweak they use.
What Jack’s formula a you currently using?
The conventional 321 is 3.6g part A, 2.4g part B, and 1.2g Epsom salt - all per gallon.
Jacks 321 nutrient schedule is 3.8g part A, 2.5g part B and 1.0g Epsom salt.
I have hard water with a ppm of around 200 so I modified the basic formula to
3.8g part A, 2.2g part B and 1.2g Epsom salt. A little less calcium and keep Mg level up.

A commonly used flower formula mentioned earlier adds MKP (monosodium phosphate - 0-52-34) during the first three weeks of flower. The per gallon application rates are:
Part A - 2g
Part B - 2g
Epsom - 2g
MKP - 1.2g

I tried Jack’s Blossom Booster. It made a mess in my autopots and otherwise not impressed with it. I have a couple containers of it and a couple pounds of finish that I never used. I prefer to add Advanced Nutrients flower enhancers and of course microbes from seedling to last feed.


Just correcting simple typo Mono- Potassium Phosphate. but sodium = bad.


I like my cannabis tasty - don’t you add MSG?
Thanks for the correction


I did see that and was wondering.

So if I understand this, I need to reduce the Nitrigen level which slows the veg growth and increase the Calcium and Magnesium which would bring the Phosphorus up to increase flower/fruit in the plant.

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For jacks the only reduction is a modified flower recipe reducing jacks and adding MPK and only the 1st 3 weeks of flower then it’s back to full strength jacks alone :love_you_gesture: