When it comes to growing cannabis, few things are as misunderstood—or as important—as pH. Whether you’re growing in soil, coco, or a hydro setup, getting your pH right can make all the difference. Even the best nutrients can’t help your plants if they can’t absorb them, and that’s exactly what happens when pH goes out of range.
What Is pH, and Why It Matters
pH measures how acidic or alkaline your growing medium or water is, on a scale from 0 to 14, with 7 being neutral. Anything below 7 is acidic, and anything above 7 is alkaline.
Cannabis prefers a slightly acidic environment because it allows roots to take in nutrients efficiently. If the pH is too high or too low, certain nutrients become “locked out,” meaning they’re present but unavailable to the plant. This can cause yellowing leaves, purple stems, or other deficiency-like symptoms even if you’re feeding correctly.
The Right pH for Different Grow Methods
For traditional soil grows, a pH between 6.0 and 7.0 is ideal, with 6.5 being a good target. Soil naturally buffers pH swings, but it’s still smart to check it regularly.
If you’re growing in coco coir or another soilless mix, aim for 5.8 to 6.2. Coco behaves more like hydroponics—it doesn’t hold nutrients the same way soil does, so pH levels need to be more precise.
For hydroponic systems, including deep water culture or aeroponics, shoot for 5.5 to 6.0. Nutrient uptake happens quickly, but the pH can shift fast too, so daily monitoring is essential.
If you use rockwool or other inert mediums, the range is similar to hydroponics. Just remember rockwool starts with a high pH out of the box and needs to be soaked in pH-balanced water before planting.
How pH Affects Nutrient Uptake
Think of pH like a gatekeeper. Each nutrient—nitrogen, phosphorus, potassium, calcium, iron, and others—has a specific range where it’s absorbed most efficiently. If the pH drifts too far, some of those gates close.
When pH is too low (acidic), micronutrients like iron and manganese get absorbed easily, but calcium and magnesium become less available. When pH is too high (alkaline), it’s the opposite—micronutrients lock out and deficiencies start to show. Keeping your pH steady within the ideal range ensures everything your plant needs is accessible.
How to Test and Adjust pH
Testing pH is simple but should become a routine part of your grow. You can use a digital pH meter or an inexpensive color test kit. Always test both your input water (what you feed the plant) and your runoff water (what drains out of the pot).
If your pH is too high, you can use a product called “pH Down,” which is typically phosphoric acid. Some growers use natural options like lemon juice or vinegar. If your pH is too low, “pH Up” (potassium hydroxide) or a tiny bit of baking soda can raise it. Adjust slowly—overcorrecting can stress your plants.
Common pH Issues
One of the biggest problems growers face is pH lockout, where nutrients are in the soil or water but can’t be absorbed. The plant shows signs of deficiency even though you’re feeding it properly.
Another issue is pH drift, which happens when your solution’s pH gradually changes over time, especially in hydro systems or coco. Finally, over-correcting with too much pH Up or Down can cause wild swings that stress your plants. The key is consistency—small, steady adjustments work best.
Pro Tip: Track Your pH Over Time
If you want to grow like a pro, keep records. Logging your pH readings for feed water and runoff helps you see trends and catch problems before they become serious. The PLNTRK app makes this easy—you can scan your plant’s QR tag and log pH, nutrients, and other details on the spot. Over time, those notes become a roadmap to your best harvests.
Final Thoughts
Keeping your pH in the right range might seem like a small detail, but it’s one of the biggest factors in cannabis health and yield. Balanced pH means your plants can access everything you’re feeding them. It’s the foundation of every successful grow—whether you’re tending a single plant in your closet or running a licensed facility with METRC tracking. Keep it steady, stay consistent, and your plants will thank you with healthy growth and bigger buds.
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