Ph of Pro mix before planting newly germinated seeds

I put pro mix in a one gallon pot. Put filtered 8.9 ph water in and the runoff was 5.2. Ran 1/2 gallon through and eventually runoff was 5.7. First light feed is with 6.1. Only used 30 drops of ph up to get it there. Last two crops I was using up to 15 ml. I’ve always seemed to have slow growth. If nitrogen doesn’t uptake well until 6.5 why would 6.0 be recommended ?

Pro Mix is a soil less mixture

@MacGyverStoner Bergman’s Lab Science Officer May '14
Soil and hydro are different animals, so to speak. In hydro you want to keep your PH about 5.5-6.0. In soil about 6.0-7.0. And as I’ve not grown every strain, I can’t say there is a good average range for all. Specific strains will likely prefer slightly different PH. You can read up on the various reasons why soil and hydro are different, but in general this is what has been found to be best. Soil tends to buffer the nutrient solution a little bit and in hydro it’s straight to the roots, this and the way the beneficial microorganisms act differently in each medium at the roots – contribute to these differences. One of the reasons in soil you don’t want to go too acidic is, especially when planting seeds, too acidic of soil tends to germinate mostly male plants and maybe male hermaphrodite flowers on female plants. The reason Robert said 6.2 PH for flowering is because in “full flower” with a healthy plant, the plant tends to turn the soil or hydro acidic because of the way it is pulling nutrients out of the medium. Bringing the soil up to 6.2 makes it a little more alkali to compensate for the plant kinda turning things towards the acidic. The “graph” referenced to in Robert’s statement was not actually up or on display on the page last I checked. But I’ve seen similar graphs, in general the more acidic you go the more absorbent – iron, manganese, boron, copper and zinc become and the more alkali you go the more absorbent potassium, sulfur and molybdenum become but the that leaves out nitrogen, phosphorous, calcium and magnesium which are all best absorbed in the middle. Don’t over think it, keep your medium between those recommendations and you’ll be fine.


Thank you kabongster.I found today Roots organics only needed 30 drops of up to get back up to 6.1. Drainage is now 6.3. I’m excited to think that I won’t need much or no ph adjuster. I’ll try less ph up next time.

just to be sure, soil less is treated like hydro(ponic).

I may be missing a lot of info. I haven’t done much research on hydroponics. Just that soil should be 6.5 - 6.7 or so and hydro is , well Ron B sent out an e-mail saying to keep it at six.

I hope cause I have my seedlings in 6.2 - 6.3.

That pH is fine for the babies, closer to 6 when they get to the 3rd or 4th node as they enter vegetative stage.
@latewood or @garrigan62 I think use pro mix

I’ve brought them in for advice

Very good, thank you for that advice.

these were with plain jane promix at around 7.0. That’s probably why they were so yellow through most of their life.


environment first…light, humidity, temperature…then pH, pH, pH…

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Second try was with infested clones. Almost a total loss. Thanks to myco I didn’t lose all, so this time I’m trying to figure out what I did do right with the first one cause this time I have good seed from Mr.Bergman. :slight_smile: so excited

Read, knowledge is power, ask questions, do searches on topics…even if the search gets off topic, it is still informative.
The only negative, sometimes you ask three people one question, you could get three different answers.
It’s hard to determine if what you know is the truth or some misinformation.
Unless you have clones, every plant is different, even the ones from the same batch of seeds.

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How is 72 for a temp at this stage ?Uploading…

Sounds good…a few degrees warmer, not much cooler.

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K, thanks.trying to upload a pic.

we like pictures

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Sorry for being late but better later then never …lol,
Now I’m new with this so just keep that in mind but, i learned from Mr. Latewood and he may correct me with a few or maybe not which would be good for the both of us…lol
But I do do my best when I can .
So with that being said here ya go @rjw71

Pro-Mix Potting Soil
You can play with the amounts, which is the nice thing about making your own mix. This should get you started:

10-20% Perlite: for added drainage and soil aeration. Use closer to 20% for flowering mixes.

10-30% Worm Castings: for nitrogen, added micronutrients and aeration.

1-2% Dolomite lime: Pro-Mix BX Seed and Clone has this already added! So I don’t add it. Basic Pro-Mix, to my knowledge, does not. Dolomite lime helps stabilize the pH of the soil. Pro-Mix is mainly peat and as the peat breaks down the soil gets more acidic. Dolomite lime is used to combat this natural lowering of the pH.
2-4% Kelp meal and/or Guano: For additional macro/micornutrients.

B Safe


Thank you for that , garrigan62

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One of my pics showed up earlier in this string of conversation. #10

If you need help with clones feel free to ask me.
Believe me I do not brag but I do know cloning. I grew 5 generations of White Widow and currently have 60 clones And 8 different strains in witch I’m going to breed. Busy busy busy lol.
O if ya need some help I’ll be glade to share

B Safe