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best pH meter for indoor plants
If you’ve tried every type of fertilizer under the sun on your houseplants and still notice signs of stress, it’s time to check your soil pH! Most plants do best in soil with a pH range between 5.5 and 6.8, which creates the optimal conditions for plant roots to soak in all the good stuff.
If you ignore your soil pH altogether and keep fertilizing your plants, you risk causing salt build up in the soil, worsening the pH imbalance and killing your leafy friends with fertilizer burn 😮
When the pH of a solution is too low or too high, certain plant nutrients will become unavailable to plants. This is known as nutrient lockout. For example, at a pH of 4.5, phosphorus becomes unavailable, while at a pH of 9.5, nitrogen becomes unavailable. This can be a major problem for plants, as it can limit their growth and development.
Keeping an eye on pH levels is even more important for hydro-growers, who rely on accurate readings to time and dose liquid feedings. pH levels shift much more quickly in hydro and semi-hydro growing media than in soil, so a reliable pH meter is a must-have for any grower working with these conditions.
Luckily, it’s pretty easy to learn how to use a pH meter!
In this guide, we recommend the best pH meter for a variety of growing scenarios, from digital pH meters to good, old-fashioned manual pH test strips and combo meters that track temperature as well as pH.
Here’s what we recommend:
|1||best overall pH meter: Apera Instruments pH 20 Waterproof pH Tester Kit||4.5 out of 5||view on amazon|
|2||best bargain pH meter: VIVOSUN 3-in-1 Soil Tester, Plant Moisture Meter Light and PH Tester||4.1 out of 5||view on amazon|
|3||best professional pH meter: Hanna Instruments HI 9813-6N Waterproof pH/EC/TDS Temperature Meter||4.4 out of 5||view on amazon|
|4||best heavy-duty pH meter: Kelway – HB-2 Soil pH and Moisture Meter||4.2 out of 5||view on amazon|
|5||best pH meter for hydroponics: BlueLab pH Pen||4.5 out of 5||view on amazon|
|runner up: Garden Tutor Soil pH Test||4.2 out of 5||view on amazon|
the best pH meters for indoor plants
1. best overall pH meter: Apera Instruments pH 20 Waterproof pH Tester Kit
key specs: temperature and pH readings | pH pen tester | powered by electrical potential (AAA battery powered)
This pH meter kit from the testing supplying company Apera Instruments is an excellent all-around choice for maintaining healthy soil with regular pH testing. Made from high-quality plastic and powered by AAA batteries, the digital screen is easy to read and the single-pronged probe is clearly designed to last more than a growing season. We recommend swinging for the full kit, which includes a carrying case and storage solution, to maintain the life of this quality product.
- Fully waterproof
- Comes with a full kit, including pH meter, storage solution, and a carrying case with very cool lanyard 😎
- ±0.1 pH accuracy in temperatures ranging from 32° to-122°F and automatic temperature compensation
- 6-month warranty
- Customer service isn’t on point: Many reviewers report non-response when attempting to collect on the warranty
2. best bargain pH meter: VIVOSUN 3-in-1 Soil Tester, Plant Moisture Meter Light and PH Tester
key specs: soil moisture/light/pH tester | high-strength plastic | powered by electrical potential (no batteries required)
This is probably the pH meter that comes to mind when you imagine pH meters in general. It’s handy, it’s cheap, and it’s definitely popular with your average indoor gardener. Don’t expect accurate readings from this device though. The simple, manual meter will guide you to catching major imbalances, but won’t catch subtle shifts in pH. Read our tips below for how to get the most accurate measurement from this tool.
- Moisture range of 1-10 (dry to moist), light intensity of 0-2000(low light to strong light) and pH level of 3.5-8.0
- Handy, one-and-done guide for checking up on your houseplants
- 10.8 inch probe will reach the root zone of most potted plants
- Not waterproof: Designed for testing soil ONLY
- Not really accurate, especially in alkaline soils
3. best professional pH meter: Hanna Instruments HI 9813-6N Waterproof pH/EC/TDS Meter
key specs: measures pH, electro-conductivity (EC), and total dissolved solids (TDS) | hand-held pH meter | 9V battery powered
When nothing but the best will do for your growing ambitions, this pH meter from the veteran analytical instrument supplier Hanna Instruments is your best option. It delivers accurate EC readings within a range of 0.00 to 4.00 mS/cm, TDS readings from 0 to 1999 ppm, and full scale pH measurements. Its crisp LCD screen is a standout feature. Paired with six buttons plus calibration dials, the large display and controls are easy to read and offer a seamless user experience. Do examine the probe before setting this pH meter up at home though – many customers report defects.
- Easily readable LCD screen
- Comes with meter, probe, 1 meter cable, calibration solution, cleaning wipes, a hard carrying case, battery and detailed instructions
- Most durable device on our list, functioning in a temperature range from 0°- to 140°F and
- Super accurate, delivering readings from pH 0 – pH 14 with a resolution of ±0.1
- Some customers experience issues with broken or defective probes, which is irritating at this price point
4. best heavy duty pH meter: Kelway HB-2 Soil pH and Moisture Meter
key specs: pH and moisture meter | pH pen tester | powered by electrical potential (no batteries required)
There’s nothing better than a product that just works. And that’s exactly what you get with the Kelway soil pH tester and moisture meter. This two-in-one product looks and feels like a heavy flashlight with a tapered end, making it an excellent pick for gardeners who plan to test pH indoors and out, and anyone who just tends to break things: This meter is designed to stand up to rough handling, unlike the meters with thin probes that tend to snap on contact with hard surface.
- With the size and weight of a flashlight, you know from picking it up that this thing is solid
- Super easy to use! Simply switch functions with the press of a big white button
- Measures pH values from 3.5 to 8.0 with an accuracy of ±0.2 and soil moisture from 0-100% with an accuracy of ±10%.
- Comes with a cowboy-style pleather carrying case 🤠
- At 6-1/2″, this probe might not reach the root zone of your larger indoor trees and houseplants
- The recommended proprietary conditioning film is unfortunately not included with this pH meter
5. best pH meter for hydroponics: BlueLab pH Pen
key specs: temperature and pH readings | pH pen tester | powered by AAA batteries
When growing hydroponic plants, gardeners rely on dependable, accurate pH readings – sometimes on a daily basis. The BlueLab pH Pen is a gold standard in the hydroponic tool kit department, guaranteeing auto-calibrated readings with a ±0.1 resolution. The BlueLab pH Pen is a fully waterproof, soundly-engineered digital pH meter that won’t disappoint. The probe does require maintenance with KCL solution and calibration solution that are both sold separately, so make sure to consider this expense in your budget!
- Fully waterproof and ideal for testing hydroponic media (floats in solution)
- Easy two point calibration with included calibration solutions
- Automatic temperature compensation
- Full 1-year warranty with proof of purchase
- Does not include the calibration solution, cleaning solution, or KCL hydration solution required to use the pen
runner up: best manual pH testing kit
best manual pH test kit: Garden Tutor Soil pH Test
key specs: simple pH strips | 100 single-use pH strips | colormetric results
Our guide to pH meters wouldn’t be complete with the backup test that every serious gardener has in their kit: Regular old pH test strips. pH test strips never run out of batteries or calibration solution, they can’t break, and they’ve been around for ages, so are generally quite reliable within their stated range of accuracy. We recommend keeping a pack of these on hand to cross-check unusual results from your pH meter.
- Super affordable!
- Delivers accurate results within the pH range from 3.5-9.0
- Results in 60 seconds
- Comes with instructions for correcting pH imbalances with lime and sulfur application
- Single-use tests generate more waste and require re-stocking
- Delivers results within a limited pH range
still unsure which one is best for you?
There are lots of pH meters out there and the price range is seriously wild. If the choice between digital pH meters, manual pH meters, or just plain old pH test strips has your head spinning, we’ve rounded up some information to guide your decision. We’ll start with a primer on why it’s a good idea to measure soil pH in the first place and what to do about imbalances, and then get nitty gritty about the different types of meters, how they work, and best practices for calibrating and caring for them.
what’s the ideal soil pH, anyway?
So what are we going for when testing soil pH? No matter what type of soil (or soilless soil) you’re working with, the sweet spot for growing most plants is within the pH range of 6.5 to 7.5. This is the zone where most macro- and micronutrients are available for uptake by plant roots, but some plants prefer more acidic soils, like blueberries, while others vibe with alkaline soil, like lavender.
So once you hit the ideal soil pH, how do you keep it that way? Some pH testing kits, especially those designed for hydroponic growing, will come with a pH buffer solution that stabilizes the pH of a growing media once the ideal soil pH is reached. Gardeners will sometimes amend soil with dolomitic lime, though this can also raise the soil pH above neutral depending on your starting point.
what to do if your soil is alkaline
Soil is considered alkaline if it has a pH above 7.0. Slightly alkaline soil isn’t cause for concern, but you should make some changes if your soil pH meter returns readings over 7.5. There are a few things you can do to re-balance your soil in this case. If your plant is visibly suffering, consider repotting your plant in a buffered soil mix. If your plant is close to death, however, avoid repotting (at least right away), since this could send your plant’s roots into shock. For an immediate fix, use a soil acidifier / pH down amendment like horticultural aluminum sulfate as directed and stop fertilizing your plant until it recovers.
When your plant is ready to re-pot, make sure your soil mix includes some of the following amendments to prevent the pH from rising into the danger zone again. It might also be a good idea to test the pH of the water you use to hydrate your plants and switch to a lower-pH fertilizer than whatever you were using before.
what to do if your soil is acidic
Acidic soil is a more common challenge for gardeners than alkaline soil. One of the most common reasons that soils take a sour turn is the use of fertilizers high in phosphorus and sulfur that build up in soil over time. To rescue plants suffering from acidic soil, sprinkle 3 Tbsp of dolomitic lime over the soil for every 6″ of plant diameter and water gently.
Once your plant is healthy enough for a new home, mix up a DIY potting soil that includes some of the following amendments to keep your soil from returning to an acidic pH:
good to know💡 pH meters with probes
When using pH meters with probes, there are a few things to keep in mind when testing and maintaining your tool. Probe-style pH meters for gardening are typically either single-pronged or double-pronged, and they work by picking up the electrical current present in soil.
Both contain electrodes that interact with the electrical charge of soil. Acidic soil (below pH 7) contains more positively charged hydrogen ions than alkaline soil, and this is exactly what soil probes measure when they take a pH reading.
- Two-pronged pH probes are typically un-cased and cheaper to produce the single-probed pH meters
- Single-probed pH meters actually contain two electrodes, just like their two-pronged cousins, encased in glass or metal to protect the elements from breaking
Probes meters measure the voltage (a measure of the pressure from an electrical circuit’s power source that pushes charged electrons through a conducting loop) flowing between the two electrodes. In both single- and double-pronged probes, one electrode contains a known voltage and the other is a “dummy” probe: Its picks up the voltage of the soil.
Because probed pH meters are electrically charged, they tend to attract other molecules that can damage or degrade the probes over time. Keep your probes in tip-top shape to get the most accurate readings with these maintenance tips:
- Clean the probes according to the manufacturer’s instructions, using a probe cleaning brush, wipes or distilled water after use
- Do not leave the pH meters in soil unless instructions tell you otherwise
- Replace budget probe-style pH meters or send them back to the manufacturer for repair when you notice rust and salt build-up on the electrodes to keep getting accurate readings
how to get the most accurate soil pH measurement
- water plants thoroughly before pH testing: Water has a significant effect on the pH of soil. The water you use to hydrate your plants can have a pH range of anywhere from 6.5 to 8.5, depending on its mineral and chemical content. To control the effect of water on your pH results, always test immediately after you water your plants – and use room temperature water (read below for why)
- always test at room temperature: pH values have an inverse relationship to temperature, meaning you’ll get higher than usual pH measurements when it’s a bit cool and lower than usual pH readings when it’s toasty. Before taking a pH test, make sure that the water, your plant’s soil, and the ambient temperature is somewhat average to get accurate and consistent readings.
- calibrate your pH meter: pH meters can fall out of calibration if exposed to extreme temperatures, humidity, or liquid (if they’re not waterproof). Even without damage, the electrical charge of meters with probes will weaken over time simply by exposure to elements.
Q. what is the most accurate type of pH meter?
If accuracy is top priority for you, we recommend choosing amongst digital pH meters that report reading within ±0.1 and have features like automatic temperature compensation, auto calibration, and come with a warranty from the manufacturer. Look for products that function in a wide temperature range and deliver pH readings on the full scale (many cheaper models won’t read anything below 4.0 or above 9.0), and be prepared to spend $50 or more.
Q. how do I know if my pH meter is accurate?
The easiest way to know if your pH meter is delivering accurate readings is to test it with a known substance. If you’re using a waterproof pH meter, test its reading against distilled water, which has a pH of 7. If you have a non-waterproof pH meter that doesn’t have an automatic calibration function, then you unfortunately can’t tell if it’s accurate. Advanced pH meters typically come with a complete kit for calibrating that includes calibration solutions for two- or three point calibration. The logic is the same though: You test the meter against substances with a known pH to calculate the accuracy of readings, and then calibrate according to the results.
Q. how often should I calibrate my pH meter?
If you’re working with plants in soil, it’s generally a good idea to calibrate your pH meter once a month. If you’re growing plants hydroponically, though, you’ll want to calibrate daily to make sure you catch any pH swings before they do damage to your plants.
There you have it. Purchasing a pH meter isn’t just about building out your plant care kit to be the envy of your houseplant enthusiasts (LOL no judgements if that’s your jam though). These handy tools come with an investment in understanding how plants work, and why it’s worth understanding your soil’s pH in the first place. Before long, you’ll be mixing up your own DIY soil (like us) to give your plants the perfectly-balanced nest they deserve. So go forth, and build a soil that would make your parents proud!
SOIL pH METER REVIEWED BY A SOIL SCIENTIST. HOW TO USE A SOIL pH METER PROPERLY REGARDLESS OF BRAND https://www.youtube.com/watch?v=evbDMRvUFpQ
🎖️ why trust us?
The list of products featured within this post was all researched, compiled, and written by Brody Hall. Brody is a freelance writer, Environmental Scientist, qualified Horticulturist, and serious indoor plant enthusiast. All of the products he featured within this list were chosen for their industry-leading design, superior performance, and application to indoor growing requirements.
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