Ph of 7.8 in late flowering , what can I do to bring down?

I’m in late stage flowering and the ph Keeps going up to 7.8. Last week I flushed numerous times with ph water of 6 and got the ph down to 6.9. The plant was very happy and began flourishing again and the buds were getting bigger. Now the ph is at 7.9 again. I really don’t want to keep flushing. Anyone have any suggestions to get the ph down. I checked the ppm and the plant is eating cause I fed it 1000 ppm after the feeding 7 days ago and it’s 200ppm in the slurry test that gave me the 7.8 reading this morning that I am referencing. Any suggestions?


Interesting. pH generally trends down rather than up later in the grow after salts build up.

As for what you can do - what soil are you growing in? A good flush will correct pH in the better cannabis specific soils.

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I’m growing in fox farm soil. I made a mistake though in the vegging stage by adding dole mite lime into the soil cause at this point the ph would range low 5.4-5.0. I don’t know if this is why the ph is ranging high now. But this was before the flowering stage so I’m not sure .

I use dolomite lime as a pH buffer. Never had a problem with it.

FF soils should correct to ~6.5 with a flush.

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I would ask how are you measuring the pH? If you are using one of those meters with the two long probes, they are famously inaccurate. I would suggest a slurry test to determine where the pH of your soil really is.

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I’m doing slurry test with a digital reader.

Are you using FF nutrients? If so, you may need to do a Sledgehammer flush. It will wash away the salt buildups.

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I’m using bergmans nutrients from ilgm website. They come with the white widow auto seeds.

I just ordered some sledgehammer off Amazon. Says it will be here tomorrow. In the meantime I’m going to flush with a water ph of 5.5. Maybe even 5.

Good luck. Here’s the way FF says to use Sledgehammer:

Thank you for contacting FoxFarm, I’m happy to help!

To perform a flush with the Sledgehammer product, you will want to prepare the mixture at a rate of 2 tsp per gallon of water. You will use the Sledgehammer standalone. Pour the solution over the soil and use about twice as much solution to flush as you would if you were normally watering or feeding. For example, if on a normal watering you use a half gallon, for a flush you would use a whole gallon. Once this is done, let the soil dry completely. After that you can pick up with the next feeding as scheduled.

If you have any other questions please do not hesitate to contact us.

Last calibration on the PH pen and have you been feeding or watering to run off each time? Have you checked run off numbers to compare those to the slurry test. soil from the root zone with equal amounts of distilled water, stirred and rested for 24 hours is the accurate way for a slurry test. Was that your method?

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