Understanding pH and TDS


I’m a newbee here in SW Lower Michigan. Waiting for the grow season to begin. Trying to absorb as much knowledge as I can. I understand the importance of pH in soil and water. I will be growing outdoors in 5 gal cloth pots, autoflowers. Will be using Happy Frog soil and a autoflower super soil additive. I do not understand the TDS and PPM side of this. Is there a good and bad. If so, what to do. Thanks for all your help.

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@bep welcome to the forum.
Total dissolved solids is what it stands for and parts per million. Both are a similar form of measurement, with different words. This is a measurement of how much nutrients is in your solution.
PH is important to keep in range for proper nutrient uptake. 6.2-6.5 for soil.

SW area is beautiful.

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Absolutely there is a good and bad. I believe pH for soil is 6.2-6.5, I’m not sure, I’m in hydro. Regardless, each has an optimum pH range. If your pH is NOT in range, your plants can’t absorb your nutrients. If not corrected, they will die. There isn’t a SET number for TDS, just recommendations. Some strains require more than others. pH is pretty much a SET number. Hope this makes sense

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Growing outdoors is a different animal. You can’t adjust pH of rain water, and PPM for outdoors pretty useless. pH and PPM much more relevant in an indoor grow.
I grew a ILGM White Widow outdoors last summer. I used tap water when I gave the plant nutrients, but was pretty spotty with the care of it. (Left it to fend for itself for the most part). The reason it was outdoors at all is because I thought the seedling wasn’t going to make it and it surprised me. I already had a replacement plant for indoor grow so outside it went.
Pay attention to the rain and water if the plant isn’t getting enough. Read up on outdoor pest and wathc for bud rot. It will be ok
You can also Google for sunrise/sunset times in SW MI which will tell you when daylight will trigger flower. (Harvest in Oct. in SW MI for most).

Good luck :slight_smile:
By the way, you will want to do a hydrogen peroxide wash when you harvest. Check YouTube for directions. This removes dust, insect/insect droppings and ect.

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Yeah, I didn’t pick up on the part about it being outdoors. Even outdoors, pH is significant. Your soil may be fine. In my area, the soil is very acidic and requires lime, but it’s nothing like indoors. I grew some outside one time about 30yrs ago. Used tap water and Miracle Grow. Didn’t have a clue what pH and TDS we’re. They did alright. Probably could have done a lot better


I should have mentioned I am in SW Michigan also. :thinking:

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OK. I understand the pH. The TDS is what’s throwing me.The TDS range is what. My city water here is about

155 PPM. Is that good or bad. I also have a hose water filter I was going to use to remove come of the chlorine and the clean some of the contaminates from the water. I also know that leaving the water in a container for 24 hours will remove the chlorine. Should I not use the filter to remove some of the contaminates and just pH the water and use as is? Thanks

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I use a water dechlorinator, but I’m inside. The best advice I can give you is “listen to your plants”. I always start with 1/4 strength of manufacturer’s recommendation and go from there. It’s much different growing outside I know, so let’s ask @FloridaSon and @Big123


It’s actually 6.2-6.8, with 6.5 considered the sweet spot.


Your water being 155PPM has very little dissolved solids and practically no buffering capacity for pH so I would use the water straight out of the tap. If you add nutes you need to verify the pH.


hey @BEP welcome to the forums from another michigander… coldwater area. i think you will do great with your autos growing outdoors here. I believe that is the best use of strategy for doing autos. i grow indoors but am real interested in seeing how outdoors works for our neighborhood. lots of great help on here so don’t be afraid to ask. most of us started where u are at. good luck on your grow!
oops also, if you put an @ in front of a name it highlights it and lets them know about it @BEP

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Hi, I’m in central Wisconsin. Greenhouse w/ plants in ground. Live on an abandoned farm. Found bulldozed pile from barnyard (50 yrs. old).I dig 5 gal.x8 per yr. Use for potting & building soil in greenhouse that and Miracle Grow.My 4th yr now. They get @ 11ft in 8.5 ceiling!