First grow, jacks nutes, could use some guidance

I started my first grow in a 3x3 tent. 10gal pots, fox farm soil (if I joined this forum sooner I would have probably done coco) but I originally bought FF dirty dozen and now realize it’s not very good so I’m going with Jacks instead (thanks to this forum) I just need some (maybe a lot) guidance.

I see people say to follow jacks 321 but that I only need A,B, epsom salt, & Mkp.

I have seen some say I need silica as well.

Lastly, I’ve seen some people say just stick to the 321 exactly and then some say stick to it until flower and then the first 3 weeks switch to a different ratio and switch back after 3 weeks.

Hoping to be blessed with wisdom, many many thanks in advance!


Jacks is a complete product and MPK is unnecessary. It is more likely to cause problems than it is to help. I would avoid it.

Silica is useful, but don’t overuse it. It strengthens plant cell structure and can make a plant hard to train. I use it after flowering starts and training is done. Silica is also helpful for trichome development.

Most growers stick with the 321 recipe as-is throughout the entire grow.

How many plants and what do you have planned for lighting?


You have 2 usernames. Suggest picking 1 and sticking with that. The admins will usually delete duplicate usernames. It is easier both on you and on the forum.


I run Jack’s 3-2-1 with silica in coco. Normally I use 3 gallon fabric pots with Autopots indoors.

I run silica from day one and no issues with hardening off until flower. I also do a modified program with MKP right at transition for 21 days then resume original nutrient program. Yields average 12 oz of dried flower per plant.


Do u have a TDS meter? Test tds runoff till it drips below 1000 before feeding the Jacks.

Limited experience, but I just grew a plant in 2 gallons of coco with Jacks 321, and silica for a few weeks. I feel like I read it is bad during flower so I cut it out. First grow in 10 years and first proper grow ever, but I got half a pound off of it.

Just followed the recipe, half strength.

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Okay, I ordered a tds meter. So you guys are watering to 10% runoff. Does that mean if I put a gallon 128oz, I should get 12.8oz to run off. And then I test that run off with the tds.

Once it’s under 1000 I should run jacks.

My question now is, would I need to be testing the runoff after feedings every single time or do you only test when issues come up or when checking to see if you need to start running nutes.

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Congrats on the grow. I’ve heard silica is good during flower because it helps trichome development. I obviously don’t have experience to say which is correct but I’m sure some of the guys on here know about it.

When you’re running jacks you just do half the amount, So you’re doing 1.8/1.2/.55 instead of the 3.6/2.4/1.2 per gallon? Is that because you’re using well water instead of RO? I was curious about that because I planned to just use well water which has higher PPM so I’d have to cut the dose down…I’m curious what the ppm of the jacks feedings normally are so I can try to aim for that ppm with the well water + jacks

Trichomes are predominantly made of silica.

Yes. It’s important to maintain your runoff PPM at ~1,000. Don’t worry if you are off a few hundred here and there. You’ll get it down with some experience.

No one can prescribe exactly what quantities you will need to maintain a 1,000 PPM. Every plant is different. I had one plant that required double doses of Jacks to maintain a good PPM. The recommended dose is a good place to start.

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Okay, sorry if this is redundant but you’re saying that I should check ppm of the run off each time I water and the ppm of the runoff should be hitting around 1000 each time?

Also this is a random question for you but curious, are you topping as a training technique? I see some people swear by it and some stay away from it just curious what your thoughts on it are

Correct. Test pH at this point as well. It should be in the range 6.3 to 6.8.

I top each plant 2 to 3 times, depending on how the plant is doing. Those who say to stay away from it are probably referring to autoflowers. It can be difficult to HST autos since you have no control over when they flower.

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Test run off for PH as well?

As for mixing the feedings:
I need to add silica to room temp water first and then (if needed) PH to 7 or a little below before adding the rest of the jacks a,b&epsom salt to avoid drop out.

Does this sound right?^

As for topping, that makes sense. I always heard to top them until recently. My training plan is topping with LST nothing crazy. If you have anything I should look into please let me know.

Really appreciate all your help!


Some growers advocate a mixing order. I’ve never paid attention to mixing order myself and am not convinced that it makes a difference.

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I read that it would cause it to be more stemmy. I should have kept it because my stems all ended up flopping from the weight.

I started at 1/4 strength .9 A, .6 epsom ,.3 cal-nit

Then i went to 1/2 when it started to look hungry and that was sufficient. I do have very hard water, it started at ec .45 from the tap and ended at ~1.8

Is cal-nit also known as jacks b?

That’s my plan too. Just gonna feel it out.


Jacks has sufficient calcium in Part B. Epsom is necessary for the magnesium.

Jack’s Part B is 15-0-0 Calcium Nitrate

If you add silica later it will most often clump up on the bottom. This is a bad thing if running a rez of nutes.

Silica, Cal Mag then everything else based on it’s order. For Jack’s it’s Part A, Epsom and Part B in that order. No cal mag needed.

The 1,000 ppm is your trigger to start adding nutrients. Soil buffers differently than anything else so you can see a high salt level (3,000 to 4,000 ppm) in FFOF before it gets depleted. Using Autopots I don’t bother and don’t flush as Jack’s is ‘soft’ enough to not cause major issues.

You will also want a decent PH meter and all of the support crap that goes with it (calibration solution, storage solution etc.). Don’t go cheap on a PH meter. Apera and Bluelab are the two go-to’s.


@Kurosawa mentioned he added cal-nit, wasn’t sure what he was referring to. I think that’s also known as jacks B

I’d never seen Part B referred to as cal/nit, but it’s on the bag. lol

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Im planning to do silica, jacks A, epsom salt & jacks B in that order, does that sound correct to you? And then I saw @Growmoredank mention they run tribus and recharge on the days in between feeding.
I’m still a bit confused on how often to add jacks nutes (I plan to follow jacks321), not sure if it’s every time I water or every other time.

I was thinking I would do (silica, jacks A, epsom salt & jacks B) and alternate that with tribus/recharge every other watering but this is my first grow so I also have no idea what I’m doing or if that’s correct lol

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