The perfect PH value for Indoor Plants
pH is one of the more mysterious aspects of growing indoor plants. While indoor plants can grow outside of their ideal pH levels, the further pH strays from ideal, the less healthy the plant will be which equates to lower yields. So let’s look at the definition of pH, why it is important and what pH levels should you strives to maintain over the course of the plant’s life.
What is PH?
pH stands for the potential of Hydrogen ions in the water. The pH scale runs from 0 – 14.0, but for plant purposes we can concentrate on the levels between 4.0 – 8.5. A value of 7.0 is considered pH neutral, below 7.0 is acidic, above 7.0 is alkaline.
Why is pH Important in Growing Indoor Plants?
As you will already know, all plants require nutrients for healthy growth. They require macronutrients nitrogen, phosphorus, and potassium, as well as micronutrients and minerals including calcium, magnesium, iron, copper, and a whole lot more. If plants cannot access these nutrients, it will lead to deficiencies and other serious health problems.
The issue with indoor plants is that they are only able to take up nutrients within a small pH window, which ranges from about 6–7 when growing in soil. If the pH is lower or higher than that, the plant cannot take in nutrients, even if they are present—thus spurring nutrient deficiencies via "nutrient lockout".
In those places where indoor plants thrives in the wild, the soil is normally slightly acidic; therefore, homegrown indoor plants will also prefer a slightly acidic environment. However, the way that you grow indoor plants also plays a role in the optimal pH level for your plants. Indoor plants grown hydroponically or without soil needs an even lower pH than a soil grow.
What is the best pH level for Indoor Plants
So this is where it gets tricky, depending on what time within its growth deferent levels are optimal. But again, if you stay between a pH of six and seven you’ll be alright. Generally it is said that the best pH for indoor plants is of 6.5, a level at which all the nutrients can be absorbed.
Here’s a recap of each element and the root pH needed
| Minimum pH | Maximum pH | |
| Nitrogen (N) | 5.5 | 7.5+ |
| Phosphorus (P) | 6.2 | 7.2 |
| Potassium (K) | 5.4 | 7.5+ |
| Ca (Calcium) | 6.5 | 7.5+ |
| Magnesium (Mg) | 5.8 | 7.2 |
| Sulfur (S) | 5.4 | 7.5+ |
| Copper (Cu) | ||
| Iron (Fe) | ||
| Manganese (Mn) | ||
| Molybdenum (Mo) | 5.8 | 7.5+ |
| Zinc (Zn) | – 5.0 | 7.1 |
As you can see, all the nutrients range between a 6 and 7, making that pH range the optimum root pH when growing indoor plants in soil.
How to test PH
Managing pH level means testing the water or nutrient solution and adjusting it accordingly. This may sound complicated, but it really isn’t.
To test pH, you can use a digital pH meter, or a pH measurement kit with drops. Opinions here differ as to which method is “best”. Some prefer digital pH meters because they are accurate and easy to read, while others like the drops as they are super simple and don’t require calibration. Try them both and see which you prefer. Here are some recommendations for you.
HM Digital pH/TDS/EC/Temp meter
- Measures Potential Hydrogen (pH), Electrical Conductivity (EC), Total Dissolved Solids (TDS), Salinity and Temperature
- Five scales: pH, µS, mS, ppm 0.5 (NaCl) Scale & 0.7 (442™) Scale
- Automatic Temperature Compensation (ATC) using three temperature coefficients
- Waterproof housing (IP-67 rating)
- Digital Calibration (push button) to any point within the meter’s range
- Auto-off function, data-hold function and low-battery indicator
- Display: large and easy-to-read LCD screen includes simultaneous temperature reading
- Replaceable Sensor (model SP-C3)
- Factory Calibrated (pH/EC/TDS)
- Includes translucent cap, 2 (AAA) alkaline batteries, pH 4 & 7 calibration solutions, pH storage solution and lanyard
- Very economical conductivity and TDS pocket meter
- Ergonomically designed display to view measurements easily
- Waterproof and dustproof housing
- Stainless steel electrodes
- Built-in belt/pocket clip
Milwaukee EC65 Waterproof Tester
The C65 is a microprocessor-based conductivity tester with a rugged one-piece IP67 waterproof casing. Immersible up to the LCD. This instrument is a low-cost and easy to use meter with a replaceable electrode.
- Automatic Temperature Compensation
- IP67 Waterproof Casing
- Replaceable Electrode
- Easy to Read LCD
- Easy to Use
ECO Farm 5 in 1 TDS/EC/Salt/S.G./Temperature Test Meter
- ECO Farm 5-in-1 water quality meter can measure TDS/EC/S.G/seawater specific gravity/temperature. The measurement range is large and wide and can measure freshwater salinity and sea salt.
- This product can detect the salinity of edible salt. At the same time, it can detect the salinity of seawater. Food salinity measuring range: 0.00-25.00%, seawater salinity measuring range: 10.1-200.0ppt.
- Conductivity: Portable TDS meters can be carried anywhere to measure water quality such as tap water, RO system water, aquarium, seawater, pool water.
- Measurement Range: 0 to 10000us/cm 10.01-19.99ms 20.1-400ms /cm, Resolution: 1us/cm, 0.1ms /cm. Accuracy: ±2% of the reading
- [TDS]: measurement range: 0-1000ppm, 1000ppm to 10000ppm, 10.1-200.0 PPT (automatic range selection), Resolution: 1ppm.
How to Adjust pH For Your Indoor Plants
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Add Any Nutrients or Supplements to Your Water – always do this first because nutrients can change the pH of your water
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Gently Shake or Stir Your Water
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Test pH – this is done using a pH Pen, drops, or strips.
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Adjust pH by adding “PH Up” or “PH Down” solution. Your goal is to get your water in the right pH range for your growing medium. If your pH is too low, you need to add “PH Up,” and if your pH is too high, you need to add “PH Down” in order to correct the pH.
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Re-test to make sure pH is in proper range.
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Water plants with pH’ed nutrient solution or add water to hydroponic reservoir
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Check – Soil or soilless growers who handwater their plants should check the pH or their runoff water to make sure it’s in the right range – try to test the earliest runoff if possible. Hydroponic growers can check the pH of their water by testing a small sample from their water reservoir a few minutes later.
