How to Tell If a Plant Needs Water: Check the Potting Mix

The short answer: check the potting mix before every watering. Push a finger about two inches into the mix. If it is dry at that depth, the plant probably needs water (University of Maryland Extension; Illinois Extension). Confirm by lifting the pot, because a dry pot is much lighter. Then allow for the pot and the mix. Unglazed clay dries faster than plastic or glazed pots, bigger pots dry more slowly, and peat-heavy mixes hold more water than bark or gritty mixes. When it's time, water until water runs out of the bottom, then empty the saucer.

Why a watering schedule fails

Utah State University Extension says "there is no general watering schedule that can be recommended for all indoor plants". Light, temperature, humidity, container size and the potting mix all affect how fast a pot dries (USU Extension). The same plant can need very different amounts of water across a year:

Pots dry faster in winter when central heating lowers the humidity, and plants in a cool room need water less often than plants in a warm room (RHS).
Plants in sun or near heater vents dry out more quickly (USU Extension).
A plant needs less water after a flush of new growth or heavy flowering, and while it is dormant (Clemson Extension, HGIC 1459).

Overwatering is the risk to watch. Clemson Extension calls it "the main cause of death of potted plants" (Clemson Extension). The American Orchid Society's definition works for any pot: overwatering is when the growing medium "does not dry out fast enough" (American Orchid Society). A schedule can't see how fast your pot is drying. The checks below can.

Five checks, and which ones to trust

1. The finger test

Several extension services start with this check. Illinois Extension calls testing the soil with your finger to a depth of two inches "the best method for determining when to water" (Illinois Extension). UMD Extension uses the same depth (UMD Extension). Clemson's version is to push your finger in to the first joint and water if it's dry at the fingertip (Clemson Extension). Mixes for cacti and other succulents are the exception: Iowa State Extension says to check that the soil is dry several inches down before watering (Iowa State Extension).

2. Pot weight (the lift test)

Potting mix loses noticeable weight as it dries, so a dry pot is much lighter than a wet one (Clemson Extension; UMD Extension; RHS). It helps to lift a pot right after watering so you know what "wet" feels like. It is handy for hanging baskets and for deep pots that a finger can't fully probe.

3. The tap test

Clemson Extension suggests rapping the side of the pot with your knuckles or a stick. A hollow sound means water is needed (Clemson Extension). It's a quick extra check that works best on pots you tap often enough to know their sound.

4. Colour, cracks and shrinking

USU Extension suggests judging moisture by colour and feel. Mix that is light coloured, cracked and pulled away from the pot is too dry, and roots may be damaged. Mix that is dark and slimy is too wet, and root-rotting organisms may become a problem (USU Extension). Soilless mixes tend to shrink when they dry out too much, which leaves gaps against the pot wall and makes the mix hard to rewet (Illinois Extension).

5. Moisture meters: useful, not infallible

Illinois Extension says a moisture probe "can be useful, but may not always be reliable" (Illinois Extension), and Clemson says these products "vary widely in accuracy" and that fertilizer and soil type can affect the reading (Clemson Extension). Use a meter as a second opinion alongside the finger and weight tests. If you're choosing one, see how to choose a soil moisture sensor.

Check	Most useful for	Watch out for
Finger, about 2 in deep	Most pots and mixes	Succulent mixes need checking several inches down
Lift test	Hanging baskets, deep pots, light mixes	You need to know the wet weight first
Tap test	A quick extra check	Takes practice to hear the difference
Colour and shrinkage	Spotting extremes	By the time mix cracks or turns slimy, it has gone too far
Moisture meter	A second opinion	Accuracy varies widely; fertilizer and mix type affect readings

How the container changes the answer

Unglazed terracotta vs plastic vs glazed ceramic

Water evaporates rapidly through the sides of a porous clay pot, so it needs watering more often than a glazed or plastic pot (Clemson Extension). Porous clay also lets more air reach the roots. CSU suggests unglazed clay or terracotta for cacti, succulents, orchids and bromeliads, and plastic or ceramic for moisture-loving plants such as Boston fern (CSU PlantTalk 1315). Fabric pots dry quickly too (Illinois Extension). Salt deposits can also crust on the outside of clay pots (UMD Extension).

Pot size and shape

Larger pots may need watering less often (CSU). A large plant in a small pot needs water more often than a small plant in a large pot (Clemson Extension).
Don't over-pot. A small plant in a big pot leaves the mix too wet for too long (Illinois Extension).
Tall, narrow pots need a finer-textured mix to keep moisture even (CSU). Check them by weight as well as by finger.

Decorative cachepots and pots without holes

Decorative containers often have no drainage hole. CSU suggests double potting: keep the plant in a pot with drainage and set it inside the decorative one (CSU). Iowa State Extension warns never to let water sit for more than a few hours in trays, sleeves or double pots (Iowa State Extension). Lift the inner pot after watering and tip out what has collected. Pots without drainage holes carry a greater risk of root rot (Illinois Extension). More: does pothos need drainage holes, do snake plants need drainage holes and choosing a pot for Monstera.

How the medium changes the answer

Peat-based mixes

Heavy, fine-textured mixes and mixes with a lot of peat moss hold more moisture (Clemson Extension), so they need longer between waterings. Peat has a catch: once peat moss dries out, it is "very difficult to re-wet". Water can run down between the pot wall and the dry root ball and out of the bottom, leaving the centre bone dry (UC Master Gardeners). If water rushes straight through, rewet the pot:

Submerge the whole pot in a bucket of water and lift it out once air bubbles stop rising.
Or stand it in a shallow tray of water and check after an hour or two, so it isn't left sitting in water.
For large containers, trickle water on slowly enough that it soaks in instead of running off (UC Master Gardeners).

Bark and orchid media

Orchid bark mixes let plenty of air reach the roots and drain very well. As bark decays it holds more water, which is unhealthy for orchid roots, and Clemson Extension advises replacing bark media about every two years. Sphagnum moss holds moisture around the roots and can lead to root rot if it is kept constantly moist (Clemson Extension). The American Orchid Society notes that how fast the medium dries depends on airflow, humidity and light. When humidity is high, the plant needs watering less often (American Orchid Society). Check bark by weight and by looking at the medium itself. See how to water an orchid.

Gritty succulent and cactus mixes

Succulents need a sharp-draining mix that dries quickly and doesn't hold too much moisture. Iowa State suggests about one-third organic and two-thirds mineral material, in a pot with drainage holes. Check that the mix is dry several inches down before watering. Yellowing leaves and soft, weak stems can mean conditions are too wet (Iowa State Extension). Succulents and cacti need much less water than most houseplants (UMD Extension). See whether cactus soil suits other plants.

Self-watering and reservoir pots

Wicking containers water from the bottom up. Capillary action draws water from a reservoir into the mix, and the height of the overflow or drain hole limits overwatering (University of Kentucky, AEN-157). Because the water comes from below, the surface soil stays drier than the mix beneath it (the Kentucky publication describes garden-sized wicking containers, but the principle is the same in a reservoir pot). So a dry surface on a self-watering pot doesn't on its own mean the root zone is dry. Check the reservoir level and the pot's weight before you add water from the top as well. Bottom watering a regular pot works on the same principle: set the pot in a few inches of water and take it out once moisture has wicked up through the mix and shows at the surface (Illinois Extension). See bottom watering pothos.

Wilting can mean too wet or too dry, so check before you water

A wilting plant isn't always thirsty. Clemson Extension says the symptoms of overwatering and underwatering are similar (Clemson Extension). UMD Extension notes that a peace lily wilts when it needs water but can also wilt from overwatering. A too-dry plant wilts and turns grey-green, while a too-wet plant may drop leaves or turn yellow (UMD Extension). Fungus gnats can also be a sign that a plant is being overwatered (USU Extension).

Mix dry and plant wilting: water thoroughly. See reviving an underwatered pothos.
Mix wet and plant wilting: don't water. Check the roots for rot. See overwatered pothos, overwatered Monstera and fiddle-leaf fig root rot.
Mould or slime on the surface: see yellow mold in plant soil.

Watering properly once it's time

Water thoroughly. Apply water until it runs out of the bottom of the pot. That makes sure the bottom two-thirds of the pot, where most of the roots are, gets enough water (Clemson Extension).
Empty the saucer. Never let plants sit in water (UMD Extension). USU suggests emptying the catch basin after an hour or so (USU Extension).
Use room-temperature water, not cold (Illinois Extension). Clemson gives 62–72°F (about 17–22°C) (Clemson Extension).
Avoid softened water, which USU and UMD both advise against (USU Extension; UMD Extension).
Flush out salts. Brown leaf tips, slowed growth or a crust of salt at the soil line can mean salts have built up. Run at least twice the pot's volume of water through the mix and let it drain, and do this before fertilizing, not after (UMD Extension).

For individual plants, see how often to water pothos, how to water Monstera and the best soil for pothos. Our watering assistant takes you through these checks step by step.

Frequently asked questions

How deep should I check soil moisture in a pot?

About two inches for most houseplants, according to University of Maryland and Illinois Extension. For succulents and cacti in gritty mix, Iowa State Extension says to check that the soil is dry several inches down before watering.

Are soil moisture meters accurate?

Not always. Illinois Extension says probes may not always be reliable, and Clemson Extension says their accuracy varies widely and that fertilizer and soil type can affect the reading. Use a meter as a second opinion alongside the finger and weight tests.

Do terracotta pots need watering more often than plastic?

Usually, yes. Water evaporates rapidly through the sides of porous clay pots, so they need watering more often than glazed or plastic pots (Clemson Extension). CSU suggests unglazed clay for cacti, succulents, orchids and bromeliads, and plastic or ceramic for moisture lovers such as Boston fern.

Should I water a self-watering pot when the top of the soil is dry?

Not on that sign alone. Wicking pots water from the bottom up, so the surface stays drier than the root zone (University of Kentucky Extension). Check the reservoir level and the pot's weight before you water from the top.

My plant is wilting but the soil is wet. What should I do?

Don't water it. Clemson Extension says overwatering and underwatering cause similar symptoms, and wet mix that is dark and slimy can lead to root rot (USU Extension). Let the mix dry, empty any standing water and check the roots.

Why does water run straight through my pot?

The mix has probably dried out and shrunk. Dry peat is very difficult to rewet, and water can run down between the root ball and the pot wall (UC Master Gardeners). Soak the pot in a bucket until air bubbles stop rising, or let it soak up water from a shallow tray.

How to Check Potting-Mix Moisture: Soil, Bark, Terracotta, Self-Watering and More