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Soil Moisture Meters for Indoor Plants: 3 Big Dangers

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Should you be using a soil moisture meter for your houseplants? After so many people using these instruments came to me complaining about their plants dying, I wanted to give you my thoughts on using moisture meters for houseplants.

I have 3 main reasons not to use soil moisture meters, and 3 things that you can do instead of using these instruments.

why not to use a soil moisture meter

I could easily include an affiliate link and try to get you to buy various moisture meters, but I’m not going to do that. Why?

Because I would not promote something that I don’t believe in and that doesn’t work. Period. My reputation is worth more to me than that, and I would be doing a disservice to my readers!

Soil moisture meters are not only unnecessary, but they can also be very dangerous to your indoor plants!

Countless people have messaged me, both through my blog and my Instagram site (@ohiotropics), that were using moisture meters with disastrous results.

Yet they trusted them and thought that they were doing the right thing, despite their plants drooping from dehydration.

Let me give you one example of one particular case that illustrates my point very well. I wanted to share this example and then tell you what you should be doing instead of using a soil moisture meter.

The question came from a friend:

“Do you have any suggestions as to how to keep these plants from dying? I use a water meter and they haven’t needed to water them for months.”

For months! Take a look at her poor rubber plant below. It is severely dehydrated and one of the trunks appears to be completely defoliated.

And her Alglaonema doesn’t look like it suffered quite as badly, but the plant has collapsed and and is very dehydrated.

should i use a soil moisture meter for indoor plants

Why You Shouldn’t Use a Soil Moisture Meter for Indoor Plants

1. They don’t measure water content

Shockingly enough, they don’t actually measure water content!

They measure (or try to measure) conductivity. While water is a good conductor of electricity, it is not the only factor.

Depending on the composition of the soil you have, as well as the presence of various fertilizer salts that are present, you can get very different and very misleading results.

If you have a very porous, chunky mix with a lot of air, such as orchid bark mixes, it will yield very awful, misleading readings.

2. Most are junk and you can’t calibrate them

Most of the soil moisture meters available on the market are just plain junk. They’re not even worth the few dollars that you spend on them.

We’ve all seen them in nurseries and hardware stores. Don’t be tempted to buy one. Most of them will give you false readings that you simply can’t trust.

soil moisture meters

They may work initially when brand new (maybe), but they won’t withstand frequent use. Besides, any good piece of measuring equipment will need to be calibrated.

The simple fact that you can’t calibrate them against a known standard is troublesome. But what would you expect from something that only costs a few dollars?

3. It drives the wrong behavior

There are many factors that go into houseplant care, and using a moisture meter takes the thinking out of plant care and this can be very dangerous.

“My soil moisture meter tells me that it doesn’t need anymore water.” I’ve heard this so many times.

If your meter indicates “wet” and your soil is actually dry to the touch, you would likely be inclined to ignore your plant for a while because the meter told you so. When in fact the soil is dry and probably needs to be watered NOW!

Even if you do get a decent moisture meter, you’ll be paying a lot more money for something that that will be adding a lot of unnecessary work and that still may not be that accurate.

So what should you use instead?

How to Judge Soil Moisture for Indoor Plants

I’ll recommend 3 ways that you can check soil moisture for your plants.

1. Use your finger to feel the soil

Sorry to disappoint you, but no gadget is required for this one! A good rule of thumb in general is to wait to water until the top inch or so (more for big pots) is dry before watering again.

Simply stick your finger into the soil and feel it. Does it feel dry to the touch? If so you may need to water. Is it still slightly moist and maybe some soil is sticking to your fingers? Time to hold off watering.

This is an oversimplification though but is a good rule of thumb in most cases! Soil moisture requirements vary depending on what plant you have.

Some plants like ferns hate to dry out much at all, while succulents and some others like to dry out completely in between watering.

For most tropical foliage plants, this rule of thumb (pun intended!) works quite well. Though I tend to use my forefinger and not my thumb…

You’ll also want to visually look at the soil too. Does it look dry? Is it maybe lighter in color? Over time, you will be able to visually judge soil moisture by the color of the soil.

But use both your sense of touch and sight though to be sure.

In one case, I misjudged soil moisture because I only felt it with my finger, but the plant was placed too high to actually see if the soil is dry.

I did that once with my lipstick plant. It was hanging high up and I would reach to feel it. It felt a little cool, but I misjudged it since I couldn’t see the soil. So I kept putting off the watering.

After realizing that I hadn’t watered it in a while, the lower leaves were yellowing so I took the plant down. I could visually see that the plant was bone dry, so I promptly gave it a thorough watering.

If you don’t trust yourself, you can use the next method.

2. Use a chopstick

Take a plain old bamboo chopstick and insert it into your soil at least a couple inches deep.

Leave the chopstick there for 10-15 minutes.

Take the chopstick out and evaluate the color. If the part of the chopstick that was in the soil has darkened, it means it has absorbed water and you should wait to water again.

If there is no color change at all, you’ll probably want to water at that time.

You can also feel the soil with your finger as reassurance if you’re not sure.

3. Lift the pot

Another way to help you judge if your plant needs to be watered is to lift the pot.

You can learn to judge if your plant needs to be watered by picking up your plant and feeling the weight of the pot.

After you water your plant, pick up the pot and see how heavy it feels. Periodically lift your plant after a few days. If the soil has gone bone dry, it will feel substantially lighter. Especially if it is in a lightweight plastic pot.

Closing Comments on Watering Houseplants

  • Ditch the moisture meter.
  • Use your senses to judge soil moisture. Feel the soil, look at the color of the soil, lift your pot, or use the chopstick method. Figure out what works for you.
  • Overtime, the longer you grow plants, you will develop a good instinct and it will become second nature.

If you enjoyed this post, there is of course much more to houseplant care. It is important to know not only when to water, but HOW to water. You may enjoy the following blog posts that I wrote on watering topics:

Overwatering Houseplants: It’s Not What You Think!

Top Myths on Watering Houseplants

Watering Houseplants While Away on Vacation

If you don’t get watering quite right, it can result in a variety of symptoms. Here are two super-helpful blog posts that will help you troubleshoot your plant problems that are related to improper watering:

Are Your Plant Leaves Turning Brown and Crispy? Top 6 Reasons Why!

Why Are My Houseplant Leaves Turning Yellow – Tips to Fix!

Please do me a favor and share this post to social media because it will help me spread the Ohio Tropics houseplant care tips to the masses! Also, check out my shop on Amazon for all your houseplant care needs:

OHIO TROPICS PLANT CARE STOREFRONT

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Chloe Kwok

Wednesday 22nd of July 2020

Question: how to measure moisture when you have a big plant? I mean if I put my finger in soil and top couple inches is dry but the bottom or middle part may not be then I will be over water the plant. That’s the only reason I purchased the moisture meter. Please advise thank you

Raffaele

Wednesday 22nd of July 2020

Hi Chloe! That is a great question, and often something that is misunderstood. If you let the top couple inches of your soil dry out, there should be no concern at all with "overwatering." Assuming you have your plant in good light, have a decently draining soil, and your plant is not overpotted (in a pot that is too big for its root system), you shouldn't have anything to worry about. Does this help?

Ann Jones

Tuesday 21st of July 2020

I a have been depending on my moisture meter too much. Thanks for the article. I believe they are incorrect most if the time after noticing the soil was wet when it said it was partially dry.

Raffaele

Wednesday 22nd of July 2020

Hi Ann! You will see a big transformation in your plants once you stop relying on the moisture meter. I'm glad you enjoyed the article, and good luck! :-)

ROGUE

Thursday 13th of February 2020

Super helpful! I was using moisture meters but stopped months ago after noticing they were inaccurate. It makes total sense too because, science!

Raffaele

Sunday 16th of February 2020

They can be very dangerous and so many of them are just junk!

Terri

Saturday 4th of January 2020

This is just what I needed to hear. I had switched to using chopsticks but I wasn't leaving them in at all so this will be very helpful. Thanks so much, I feel so lucky to have come across this blog.

Raffaele

Sunday 5th of January 2020

Thanks Terri, I'm so happy that you are enjoying my blog!