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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.

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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.

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A Ficus elastica that has suffered from its owner relying on a moisture meter

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

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A dehydrated Aglaonema resulting from using a moisture meter.

Lastly, here is another Aglaonema that suffered from using a moisture meter.

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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.

Even if it you use tap water that has is very hard, over time, minerals can build up in the soil and your moisture meter will give false readings.

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.

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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.

Commonly Asked Questions About Moisture Meters

Can moisture meters be wrong?

Like any instrument, quality can vary drastically. Low-end, inexpensive moisture meters are notoriously unreliable. Higher end devices can be helpful, but in the majority of cases, aren’t worth the expense and trouble.

Should you use a moisture meter?

I strongly advise against using them for your houseplants. I’ve seen too many people kill their plants by relying on a moisture meter. Use the other methods described in this post as an alternative.

Are cheap moisture meters any good?

No, they are notoriously inaccurate and should not be relied upon to judge soil moisture for your plants.

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

A. Crockrell

Tuesday 29th of November 2022

Thank you so much for your unbiased, integral advice about moisture meters. I will keep using my finger and eyes and incorporate the bamboo stick.

Raffaele

Wednesday 30th of November 2022

You're very welcome! :-)

Nancy

Saturday 5th of November 2022

Thanks for this timely information about moisture meters. I’ve been trying to measure the moisture level in my potted succulents and find that my moisture meter registers dry even when the cactus soil is moist when I stick my finger in. I have so many potted succulents and houseplants that sticking my finger in all the pots sounds like a lot of work so maybe I will try to get used to lifting the pots that aren’t too heavy to judge that way.

Raffaele

Monday 7th of November 2022

And this is exactly why I don't recommend using moisture meters :-) You will be far better off using your finger to feel the soil, and also by picking up the pots like you mentioned. Good luck Nancy!

kirstyn

Tuesday 20th of September 2022

Interesting article! I think that people should rely more on the following - a thorough understanding and accurate identification of ANY plant that they purchase i.e. the exact species and what its specific care needs are- the problem there is many places fail to put care labels, much less ID information, on the plants that they sell; as such, it is no wonder that people often mistreat their plants. And many purchase high maintenance ones that are incompatible with both their environment and their lifestyle. So first step - before purchasing a plant, do some research first! If unsure about what exactly it is you are getting and how to take care of it, ask. If nobody is available, do not purchase from them.

I started indoor gardening over one year ago and am proud of the 24 plants I own, and that includes a couple of difficult species too. I was once a totally clueless killer of indoor plants! If you own a lot of plants, my suggestion is to keep track of which plant you watered and when. I created an entire spreadsheet that lists each one of the plants I own, charting things like the last time I watered, where it's positioned, any concerning changes etc, so I know what days they are on the schedule for a water check. Which means that they might or might not require another watering that day. Otherwise, I'd be cluelessly poking my plant's soil all the time. For some smaller and more delicate plants, like those succulents in their tiny 2" pots and that VERY delicate string of turtles that was IMPOSSIBLE trying to stick my finger in without breaking off the turtles, or any other plant with very dense and delicate foliage and thin vines, like a rarer hoya I own, and those that get very compacted soil and getting your finger through it is really difficult.

For those situations, I use a combination of the spreadsheet tracking when I last watered it, the plant's appearance, and how heavy the plant's pot feels - however, if it's in something other than a nursery pot or planted in a fairly heavy ceramic or other weighty material, it can be hard to tell. I've got a pink dalmation which had little white roots popping out at the surface of the soil, and the meter consistently read soil was very wet. I cut down, and starting using the finger method as a way of getting a second opinion. Still wasn't sure, but now new leaves are sprouting up and it looks overall much better. The soil meter is still pretty new, but still, I let the plant guide me on when I need to water it. People who don't know what species they're buying and how to properly care for it and don't take care to remember when they last watered their plants are setting themselves up for disaster. It's ridiculous to let a soil meter make all your plant care decisions. So for now, I think the kind I own works okay, as long as it is used as one part of overall care, and not considered to be the ultimate, error free care tool.

Raffaele

Wednesday 21st of September 2022

Hi Kirstyn! You're a very wise plant owner, and I love everything you mentioned. I talk about a lot of these in my book, Houseplant Warrior. Many people are missing observation, which you are doing very well!

Deborah Noack

Thursday 25th of August 2022

My husband says if moisture meters don't work why do they sell them?

Thank you!

Shawna

Friday 18th of November 2022

@Deborah Noack, Because people buy them. Why do people think every company actually cares if something is effective or even always safe? Some also still sell cedar shavings labelled for small animal cages when it has been proven in scientific studies to cause respiratory illnesses and stress their livers. At least one fourth of cat litters available frequently cause health problems and sometimes even for the pet owner but they tend to be the cheapest ones so people buy them without doing any research. Some companies are willing to risk the life of your pets or even their customer's health so why would they care how successful you are at keeping plants alive?

The fact people don't question products being sold, rely on them without first confirming they are effective, and often make no effort to learn about something even when caring for living things is part of the reason we had to create regulatory agencies that reduce the dangerous or ineffective products that can be sold. Their job though is not to decide how useful or accurate each brand of something like a water meter is if you decide to buy cheap and ignore common sense.

A water meter can be a useful tool but only after you understand how it works, when it doesn't work, and combine it with other methods. Our attempt at a potted growing Christmas tree has a water meter on it. After much research into how much to water a potted spruce tree I used a meter that clearly changed values when that soil was watered to help determine when I had it completely soaked and how long it stayed that wet deeper than I can get my finger into the soil around the tree roots. It is best not to repot it for a couple months until it recovers from stress so it's difficult to get anything past the roots at the moment. Now I'm currently ignoring the meter because the lower part of the pot with most of the roots remained very wet for a long time after watering with both the meter and tilting the pot to look at the drainage holes and damp area in the tray underneath being used to decide that and the top inch is still slightly damp. If I keep the area where the meter probes are at the high end of ideal moisture range like many suggest the majority of roots may be at risk of rot. If my meter reads any lower though and the very top also seems too dry I will consider whether too much of the pot is getting dry or it's had enough time without soggy lower soil to water it again.

The water meter is one tool to help in estimating soil conditions but it's useless without knowledge, common sense, and other methods of evaluating a specific plant in a specific soil mix in different types of pots with different room humidity levels. There is also a temp and humidity gauge by the tree and sitting on the soil of a few of my other potted plants that are sensitive to those things.

Raffaele

Thursday 25th of August 2022

They vary greatly in quality, and the inexpensive ones are not reliable. Much like anything, you will get what you pay for.

Tim

Tuesday 10th of May 2022

Hi Raffaele,

Thank you for this post, it is very clear and I think just what I needed to hear. I would like to ask your advice on an issue I currently have with a ficus binnendijkii (quite a large tree) that I bought about 2,5 months ago. It kept losing leaves and after 1,5 months I bought a moisture meter to see if it was due to the wetness of the earth. It showed me the moisture level was far beyond the 10 and that's why I cut the tree off from watering. The water level didn't go down for weeks, even when I took the tree out of the pot to try to let the soil dry through air exposure. So finally I decided I had to get rid of the wet earth in order to stop the roots from rotting. I now put the tree in a completely new batch of soil, didn't water it in any way and the moisture meter is still telling me it's at moisture level 10. That's when I started to seriously doubt if it was giving me the correct moisture level. And that's also why I found this post on your website. As my ficus hasn't gotten any water now in a month I suppose I've been fooled by the meter and should start watering it immediately? Thanks in advance!

Raffaele

Friday 13th of May 2022

Hi Tim! Did you feel the soil with your finger? I would definitely ditch the moisture meter and use your finger to evaluate the soil moisture. Depend on how big your pot is, I'd let at least the top inch dry out before watering again. It sounds like it may be quite a big pot though, so maybe allow the top 2-3 inches, if not a little more, dry out before watering. Hope this helps a bit.