Low PH, Yellowing Leaves

This plant shares a [Grow Box](https://www.agardenpatch.com/ with the pictured tomato plant. I have numerous other grow boxes and potted plants (all tomato) and they all have PH of around 6.5 or so.

The PH of the cannabis plant soil is 4.5. I have tried hard to raise the PH by using PH Up and also Baking Soda, adding them to the water, and I cannot get PH to budge. I used an entire pint of PH Up and 1/3 box baking soda. How can I get the PH up?

Next, look at the yellowing leaves. I trimmed off all yellow leaves just yesterday, so these have yellowed in less than 24 hours.

Can you tell what’s going on here and what I need to do?


I would not have both in a box. Poor babies are suffocating from no air in between. I don’t think she want to play with her tomatoes anymore.


They need air in between as @beachglass stated, and they could also be fighting at the root level for space. Without knowing what soil and nutrients it’s hard to tell what’s going on with ph. Most would use a flushing additive and follow with a feed to get pH back in line. That’s a lot of baking soda dumped on your soil.

The yellowing leaves could be normal aging, it doesn’t appear there are any larger fan leaves towards the top out of whack. But pH can cause it as well, especially if it’s happening overnight.

I could be wrong, but you might want to get those plants apart, if possible. If it’s the only container outta whack, and the only one with 2 different types of plants.


Baking soda raises PH.

What soil is it? Commercial potting soil like Miracle Gro? If so you won’t be able to do much with it.


If you have more than one plant in the soil, the plants will compete for resources. Been there, done that. I ended up having to garbage both due to going down hill and no way to transplant one. Never made that mistake again.


Thanks for your responses. I have removed the tomato plant, and just added, beleve it or not, another entire pint of Ph Up to the 4 gal water reservoir. At the moment the soil shows 4.5 on 2 different meters. If PH does not change soon, I’m thinking about dumping a full cup of baking soda on the soil.

Interesting point. The tomato plant had about 10 small tomatoes, and I noticed that all tomoatoes were dark brow, like rotted looking, on the lower halves. What does this tell us ??? Something aint right here.

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What are you using to measure the medium PH? If it’s one of those moisture PH combo tester, their very unreliable. A TDS pen to test the run off or a slurry test is the method most cultivators use :love_you_gesture:

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I actually have 3 cheap PH testers. I know they work because PH in other plants is around 6 or so with all 3, and all 3 say 4.5 for pot plant.

Look at my setup. There is no runoff to measure.

Are these soil probe type? Because most are truly worthless. A better method if runoff isn’t available is to run a slurry test: 1/2 cup distilled water, 1/4 cup of your soil media mixed in and let stand for 30 minutes then test the liquid.

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They are soil.
Did it your way with expensive liquid tester PH meter…same result 4.7.

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Can you post a pic of that tester? Which method, run off or slurry? If a slurry did you go deep into the root zone for the sample?

This is tester.
Did slurry and got soil deep.

Garden lime can help raise the soil ph…

What kind of PH UP are you using? The stuff I have is bloom city was cheap off of Amazon and only needs a few drops per gallon and that changes it drastically. If I had even half a cap full it cna change the PH +/- 3 or 4 easily. A whole pint for 4 gallon seems like a ton. I’m new to all this myself but was just curious

Same stuff. Used entire pint with no change. Bloom PH Up

I am really baffled about what’s going on here. I’m wondering if raising the water PH should change soil PH. That’s what I’ve been doing, and the water is PH 7 to begin with!

I added a cup of baking soda to soil yesterday. Will see how things go with it. I have lime to try too, but have not used any yet.

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Finally got PH up to 6. Now most leaves are turning yellow quickly. Somehow I screwed the pooch.