Reliably determine soil moisture for houseplants – Forget regular watering indicators!

It can be difficult to know when a houseplant needs watering. The industry has developed watering indicators for this purpose. Unfortunately, these do not always work particularly reliably. The results are often hard to read or ambiguous. Today I present you an inexpensive tool to reliably determine the moisture level of your plant soil. For about 10 euros it beats all available watering indicators.

Watering indicators avoid under or over watering

In the past, I have underwatered or overwatered our houseplants a time or two. I think no houseplant fan can deny this happens sometimes. The result was withered shoots, drooping plants, a pest infestation by fungus gnats caused by overwatering or even root rot.

To avoid this, of course, I used conventional watering indicators. You simply stick these firmly into the flower pot and the manufacturers promise that you can read the water level at any time. In reality, it often looks different. I rarely get a clear picture at the display unit. A red indicator means too little water, a blue indicator means too much water. But how do I recognize enough or even the right amount of water? This is where the blurring of conventional watering indicators begins.

Conventional watering indicator: Is that blue or red now?
Conventional watering indicator: Is that blue or red now?

These conventional indicators make use of the principle of capillary action. Moisture rises in a moisture-conducting material to the display, where it then creates a chemical reaction that sets off the discoloration to either red or blue. This is already inaccurate. Because there may actually be enough moisture in the soil, but not enough to rise all the way up to the display. If only little moisture arrives there, the display is in an indefinable state between red and blue, but does not necessarily reflect the reality in the potting soil.

In addition, the capillary action is delayed. It simply takes time for the moisture from the potting soil to reach the indicator. More accurate watering is therefore only possible to a limited extent, as this is a long-term indicator.

Accurate soil analysis with a soil tester

Recently, I have become a big fan of soil testers that determine the moisture level based on soil conductivity rather than a chemical reaction (Amazon Affiliate Link).

Unlike watering indicators, the soil tester (Amazon Affiliate Link) does not remain permanently in the soil, but is only used immediately before watering. This may be considered a disadvantage by some, since the soil tester has to be used before each watering process. On the other hand, there is no advantage of a permanent watering indicator in the pot, which then doesn’t work. For the watering process alone, I have to go to the individual plants with my watering can anyway. Just using the soil tester before is no big deal if it keeps my plants healthy.

Ideal moisture at the root ball - the old watering indicator on the right shows scrap.
Ideal moisture at the root ball – the old watering indicator on the right shows scrap.

A wide scale allows the moisture level to be read accurately. This is ingenious, because I can regulate the moisture quite granular and get a reliable result and not just a “red – dry” and “blue – moist”. I can read the result as soon as the soil tester is in the plant soil.

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In addition, I need only one soil tester for all houseplants and do not have to buy a separate one for each plant. The soil tester costs only ten euros and works perfectly (Amazon Affiliate Link).

I use the soil tester successfully in regular plant soil and also in planting substrate.

Bye bye root rot – for only about 10 euros

I can only encourage you to give this inexpensive tool a try. For only about ten euros it’s worth the effort. It has changed my life as a plant fan and I could have treated many plants better in the past. I could even have saved a few if I had had this tool at hand earlier. Root rot and waterlogging are history for me now.


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