Soil Moisture Meter

The top inch of soil can be bone dry while the roots below are still sitting in water, and that gap is where most overwatering starts. A moisture meter closes it. Push the probe down into the root zone and the dial tells you, in a few seconds, whether the soil there is wet, moist or dry.

It needs no batteries. The probe measures how well the damp soil conducts a tiny electrical current, so it works the moment you push it in. It is especially useful for large pots, where a finger only reaches the top few inches.

At a glance

• Probe length: 8 inches, long enough for large floor pots.
• Readings: a dial from 1 (dry) to 10 (wet).
• Power: none needed.
• Price: $14.

Using it

• Push the probe about two-thirds of the way down the pot, between the stem and the edge, where most of the roots are.
• Wait a few seconds for the needle to settle, then take the reading.
• Wipe the probe clean and dry after each use, and do not leave it standing in the soil.

What the numbers mean

As a rough guide, plants that like to dry out, such as succulents and cacti, want a reading of 1 to 3 before you water. Most leafy houseplants are ready for water at around 3 to 4. Ferns and calatheas prefer to be watered at about 4 to 5, before they dry further. A reading of 8 or more, days after watering, is a warning that the soil is staying too wet.

Its limits

A meter is a helpful second opinion, not a replacement for paying attention to the plant. Readings can be thrown off by very chunky or very salty soil, and they say nothing about light or temperature. Used alongside our houseplant watering guide, it takes most of the guesswork out of the decision.