Do Moisture Meters Damage Plant Roots?

Many gardeners worry about over-watering or under-watering their plants. Even plants of the same species may have different watering requirements depending on their individual environmental conditions. The moisture meter is one trusty device gardeners use to prevent watering issues, but some people may worry about its effects on the plant roots.

Moisture meters don’t damage plant roots as long as you keep them at a safe distance from the roots. You can also avoid root damage by carefully and gently inserting the probe into the soil.

If you need to use a moisture meter but are worried about whether or not it can damage your roots, read on. This article will discuss how to safely use the device, the symptoms of damaged plant roots, and how to fix your plant roots in case of damage caused by a moisture meter.

How To Avoid Damaging Plant Roots When Using Moisture Meters

Soil moisture meters or sensors are simple devices used to measure the soil’s moisture content. For home gardeners, a hand-held moisture meter is enough for simple gardening needs.

Regardless of the type of moisture meter you have, it can be easy to misuse it, potentially resulting in root damage.

Here are some steps to avoid damaging your plant’s roots while using moisture meters:

  1. Understand your plant’s root system.
  2. Don’t use a moisture meter with a rusty probe.
  3. Gently insert the probe into the soil.
  4. Let the probe rest in the soil for up to 60 seconds.
  5. Never leave the probe in the soil after use.
  6. For stationary moisture sensors, follow the product label.

Let’s discuss them in further detail below:

1. Understand Your Plant’s Root System

One of the most important things to consider when using hand-held moisture meters is the type of roots your plant has. Depending on this detail, you will need to adjust how you use the device.

The different types of roots you will have to consider include:

  • Shallow root
  • Short root
  • Taproot
  • Fibrous root
  • Bulbous root
  • Tuberous root

Hand-held moisture meters typically have one or more metal probes that send signals to a mechanism in the device that determines the level or amount of moisture in the soil. When used carelessly, these probes can puncture the roots and may cause irreversible damage.

Fleshy roots like taproot, bulbs, and tubers are especially at risk from puncture wounds from metal probes. 

Understanding your plant’s root system can help you estimate how far and how deep into the soil you should insert the probes to get an accurate reading without damaging the roots.

2. Don’t Use a Moisture Meter With a Rusty Probe

While metal rust can be a good source of iron for your plants, it can be harmful to plants that thrive in soil with very low pH (4.0 and below), such as blueberries or mums. The extremely low pH can corrode the metal probe and generate more rust. 

While it takes much rust to be a cause of alarm, excess iron in the soil can result in leaf browning and stunted root growth. If you are using your rusty moisture meter for a potted plant with acidic soil, there will be a higher risk of iron toxicity.

Moreover, a moisture meter with rusty pins or probes will generate inaccurate readings. That’s another reason why it is best to avoid using rusty probes. If possible, replace them with fresh ones or get yourself a new meter with better quality and rust resistance.

3. Gently Insert the Probe Into the Soil

The pins or probes of hand-held moisture meters are designed to make them easier to insert into the ground. That is why you don’t need to use much force to bury them to an ideal depth.

If you have plants with fleshy roots like carrots or onions, gently insert the probe into the soil, and stop when you feel some resistance. Chances are, you are about to puncture the root. Pull out the probe and re-insert a half-inch (1.25 cm) away from the initial spot.

4. Let the Probe Rest in the Soil for Up to 60 Seconds

Metal probes build up rust because you may have left them far too long in the soil. As mentioned, acidic soils are highly likely to corrode the metal and increase the risk of rusting. Although it won’t result in rusting immediately, making a habit of it can present problems in the long run.

It typically takes 30-60 seconds to get an accurate reading on moisture meters. After which, you can pull out the probe. This simple practice can help you protect your plant’s roots and lengthen your moisture meter’s lifespan.

5. Never Leave the Probe in the Soil After Use

Never leave your moisture meter on the ground, whether in the soil or on it. The metal components may corrode when you leave soil debris and moisture on their surface. In addition, the sun’s heat may also speed up the corrosion rate.

It’s pretty easy to manage a hand-held moisture meter. You just need to keep the following in mind:

  • After use, clean the metal probe with a moist cloth to remove visible debris. 
  • Then, wipe it with a dry, lint-free cloth. 
  • Store the device in a cool, dry place, free from the elements to prevent damage.

6. For Stationary Moisture Sensors, Follow the Product Label

Some moisture sensors are stationary, so you can bury them in the soil for extended periods. This type of moisture meter is typically used in bigger fields.

When using stationary moisture sensors, always read and follow the instructions laid out by the manufacturers. The instructions usually indicate ways to manage the device for optimal use while preventing potential damage to crops.

Symptoms of Damaged Plant Roots

Severe damage to the plant roots due to improper use of moisture meters is rare. Nonetheless, if your plants’ roots suffer from some degree of damage, they will show signs that can help you address the issue.

Here are some symptoms your plant has damaged roots:

  • Wilting: Depending on the extent of the damage, plants with broken roots may exhibit leaf or flower wilting. For plants with partially injured roots, wilting occurs on the side of the affected roots. So if you notice your plant’s leaves or flowers drooping and drying up a few days after using your moisture meter, you may want to check if the roots are damaged.
  • Fewer leaves on the affected side: Another sign that your plant has root damage is when there is noticeably less foliage on the side where you often use your moisture meter.
  • Short, distorted leaves. Bulbous roots (such as onions and garlic) are prone to cavities caused by nematodes. However, if you are using pesticides to get rid of them, chances are your use of the moisture meter has punctured the bulb. The cavity left by the wound becomes a target for secondary infection from bacteria or fungi, resulting in short, distorted leaves. Eventually, it can cause your plant to die.

How To Fix Plant Roots Damaged by Moisture Meters

How you should manage and/or fix root damage caused by moisture meters depends on the severity of the injury. Here are some tips to keep in mind:

  • Apply lime on soil with excess iron from rust. Lime will increase the pH of the soil and make iron unavailable to the plant’s roots. However, lime is slow-acting and may be detrimental to plants that require an acidic substrate.
  • Remove damaged bulbs or tubes. When secondary bacterial or fungal infection occurs from puncture wounds on fleshy roots, there is a risk nearby plants will be infected. It is best to remove and properly dispose of affected plants.
  • Prune wilted leaves, flowers, or branches. Plants with minor root injury from probes may show symptoms but can recover naturally. Pruning affected parts will help the plant focus on healing and regrowing healthy roots.

Final Thoughts

As the saying goes, prevention is always better than cure. Moisture meters are helpful gardening gadgets to prevent over-watering or under-watering your precious plants. They’re also pretty easy to use.

However, like with any other gadget, careless use of moisture meters may cause severe damage to your plants’ roots. Luckily, such issues are easy to avoid. Basic knowledge of your plants’ root structures and careful use of the meter probe are often enough to keep your plants safe.

To learn how soil moisture meters work without batteries, you could check out this article: How Do Soil Moisture Meters Work Without Batteries?

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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