OK, so a ton has been said about pH, and there is even a stick entitled "pH and what it means for your plants." My intention is not to delve into the science of what it means, but more of a simple, "what you need to know about pH to be successful." First, let's take a look at this chart: http://forum.grasscity.com/attachme...138497823-chart-thread-nutrient_chart_454.gif I found this chart here somewhere on this website, and I still reference it all the time. I've seen numerous charts just like it in different grow books, and all over the Internet. The fact is that no matter what anyone says, or what strain you are growing the range on that chart is pretty much dead on. I'm not going to argue that you have some crazy strain that only flourishes at a range of 8.0. I won't argue, and I won't believe you either , but the fact is that the chart pretty much holds true. With that said, I want you to understand what I think is the best way to work with pH, and why I think it's the best. Soil: In soil the runoff (that is the water that drains from the medium, after being watered) is the most important aspect in regards to pH. What you want to do is collect a good amount of runoff. I would suggest watering until about 20-50% of what you put in runs back out of the plant, this will give you an accurate reading of the real pH of your growing medium. If you water with too little, it will not be accurate enough to take a proper reading. I suppose too much is not really a problem, but more just a waste. According to our chart, in soil, a pH of about 6.5 is the perfect-world range. So what that means is every time I water my plants, I want the runoff water to be about 6.5 pH. This is obtained, and most importantly maintained, by measuring the runoff every time I water, logging that measurement, and adjusting with the pH of the water I put in on the next watering/feeding. For example, if I water my plants with a solution of 7.0, and it runs off at 6.3, the next time I water my plants I want to start with a solution of 7.2. In theory, the runoff the next time should be right around 6.5. I have personally never seen a radical change of pH in soil in terms of days, but in general as a plant develops, the pH will start to go down, especially during flowering, and heavy feeding. That means that normally, I will start a plant, and the pH of the water going in is generally about 6.8 and I maintain my runoff of about 6.5. But during heavy budding, I may water in with a range of about 7.5-8.0, to maintain that 6.5 runoff that I want. The fact of the matter is, it doesn't really matter what the range of my water in is, as long as my water out is ideal. Hydroponic: If you look at the chart for hydro, it says an ideal range is 5.8 (again you can say what you want, about your plants and your grows, I don't care, as it's not the point I'm trying to make). The nice thing about hydro is that I can easily measure, and maintain my water's pH level just by measuring it. I don't have to monkey around with collecting runoff, and keeping a log and adjusting as I go. I can literally measure as I use it. In general, when creating a fresh hydroponic solution (no matter what the system is) you start your solution at 5.8. You then let it run for a while, whether that be 24 hours, a few days, or what ever you prefer, and then measure again and adjust. Sometimes you will find that you don't need to adjust, sometimes you will have to, it just depends on the system, the plants growth, and many other factors. The reason hydro is nice in this regard, is in many different hydroponic systems, there is some sort of reservoir system, that allows you to quickly measure, and change the pH of the solution given to the plants, that means at all times you can give your plants a perfect pH range of solution. This is part of the reason why hydroponics are one of the fastest methods of growing marijuana. Soilless (not hyrdo): I call soiless not hydro because I don't consider it that. Unless you're using it just as a medium in which a hydro system is still being utilized - in which case it's still a hydro system, just using a soiless medium for it to grow in. If you're growing in something like coco, and juts hand watering, while the method is similar to soil watering, it's still in essence hydroponics, however, to me it's just not the same idea. I don't want to confuse anyone here it's the whole potato - potato thing... The idea is, in soiless mediums, you generally want to keep the same pH range as in hydroponics, but use the same system of collecting your runoff as you would in soil. You still need to monitor the water that runs out, and compare it to what you would prefer your range to be, and adjust the next time you feed with the correct pH of the water going in. To put it simply: soiless is the same exact concept of soil, except just using a different range of pH. The difference is, I have not seen the constant swings in pH that I do in soil. In general, soiless mediums are a little different than soil in terms of pH, but the way of collection/measuring is the same. Flushing: I also want to take a look at flushing, what it means for your medium, and why it should be done not just at harvest, and when you think you are experiencing issues. Flushing does exactly what it sounds like it does. It removes any sort of build up, whether that be excess nutrients, salt build up, or anything else that can get in your soil and potentially cause problems. In general, in soil, the cause of your soil's pH range going out of whack is because of mineral salt build up. Salt build up doesn't just affect your pH, but it can also lock out nutrients. Marijuana does use sodium in it's growth process, but at very minimal doses, and too much sodium (aka salt) is toxic for the plants. It also can be a key component in locking out the availability of other key nutrients. Flushing will remove excess salts, built up nutrients, and in general clean your soil out, and leave you with a fresh medium. In general I grow using FFOF soil. In vegetative growth, I have to use very little nutrients, because the soil itself has so much. During flowering however, the soil has very little left nutrient wise, and the plant can really only use what I give it. I have also noticed a trend that about mid-flowering my pH is going to be very low, and I have to water with very high ranged pH to make up for that. Therefor, I have found that one good flush, about mid-flower will help things drastically. While it won't completely fix my soil pH, it usually raises it a few tenths. Because of the way I measure my in/runoff, this isn't really a big deal, BUT I do know that the reason it's going up is because I have cleaned all of the crap that was in the soil, and am left with a clean drawing board. It's at that point, where I will start to feed the plant heavily. I know that with clean soil that there is nothing that my plant will feed on negatively, and also nothing that can affect my nutrients uptake to the plant. This allows me to feed my plants heavily, and watch and truly understand the affect that it has on them. If they are overfed (which hardly happens) then I know to cut back some. If they don't look overfed, then I hit them harder with nutrients, up until I give them the harvest flush. The most important thing to keep in mind with flushing however, is that if you do it right, you have a clean slate. You have more or less, removed everything out of the soil, and are now just using it as a medium to support your plant - all that is there is dirt and rock. From there you can control how your lady eats, and what she eats. Flushing is very important, and very underrated to new growers. Ever since I have started this system, I have found a huge increase in my plants production, and more importantly resin production. I've also found that I can almost predict what problems I will have, and avoid them before they happen. If I think a nutrient problem will occur due to pH, I can correct it before it becomes a problem. If I think salt build up, is a problem, I flush, and start with with a clean slate, that I can easily control. The biggest mistakes I see on here, aren't because of people's growing styles, it's because of pH issues. Most people know how to follow a feeding chart, and how to measure out a teaspoon of grow big. But what they don't understand is how the plant is affected in the grand scheme of things. Follow this system, along with a good grow formula, and I can guarantee you results. Have questions? Feel free to post them in this thread. Also feel free to PM me or check out my grow journal thread. I always check that thread out, and always have some new pics going up in that channel, so stop on by if you want.