First, Make Sure It's Actually Wet
Half the people typing this question have a dry plant. Peat and coir based potting mixes shrink when they dry out hard. The block of soil pulls away from the wall of the pot, and the next time you water, the water runs straight down that gap and out the bottom in four seconds. You see it drain, you feel a damp surface, and the middle of the root ball is a dry brick. The top inch stays cool and dark because it's the only part that got hit.
Go get a wooden skewer, a chopstick, or a pencil. Push it into the middle of the pot, not against the side, all the way to the bottom. Leave it sixty seconds. Pull it out and look at the whole length. Dark and clingy with soil stuck to it means wet. Comes out clean, pale, and dusty means dry, no matter what your finger said on the surface. A finger reads two inches. Roots live deeper than that.
Second check, and it's free. Lift the pot. Water is heavy. Once you have felt the same pot soaked and the same pot dry, you can tell the difference from the handle in one second forever. Cold soil also feels damp to skin when it isn't, which is why so many people are convinced their winter pots are soaked when they're actually dusty in the core.
The Three Exits Water Has, and What Blocks Each One
Water leaves a container three ways and only three ways. It gets pulled up through roots and breathed out the leaves. It falls out the drainage hole. It evaporates off the top inch. When soil stays wet for a week, at least one of those exits is shut, and usually it's two.
Gravity should finish its work fast. Water a pot properly and free water should stop dripping within about half an hour. If nothing ever came out the bottom, stop reading and go look at the bottom of the pot right now.
- No hole at all. Plenty of big box pots ship this way, and plenty of buckets never got drilled.
- A hole plugged by a solid mat of roots, or by that little mesh disc that came stuck inside.
- A decorative outer pot or saucer holding a reservoir the bottom inch of soil is sitting in.
- The pot set flat on concrete or a tray with no gap, so surface tension holds the water in.
Evaporation is the weakest of the three and it barely touches anything below the top inch. Indoors, in a dim corner, with no moving air, it's close to zero. That's why the same plant that dried out in four days on a sunny step takes three weeks in a bathroom.
Why a Plant Stops Drinking
In a growing plant on a bright day, the roots and leaves move the overwhelming majority of the water out of that pot. Everything else is a rounding error. So when the soil stays wet, the first question is not how much you poured, it's why nothing is pulling.
Root volume versus soil volume is the most common answer and nobody warns you about it. You buy a small plant in a four inch nursery pot and immediately put it in a five gallon bucket because you want it to have room. Now you have a few tablespoons of root sitting in gallons of soil. The roots can only drink from the soil they're actually touching. The rest of that bucket is a cold wet sponge with nothing in it, and it will stay wet for weeks. Then the roots grow out into that wet dead zone, find no oxygen, and rot.
The other two answers are season and shock. Short days and cool nights drop a plant's water use off a cliff. A pot that emptied itself in three days in July can take ten days in October with nothing wrong at all. And any plant you just moved, repotted, or bought has broken root tips. It will not drink normally for a week or two. That slow drying is expected. Do not respond to it by watering more.
Wilting in Wet Soil Is the Misdiagnosis That Kills
Here's where people torch their own plant. Leaves go limp, the brain says thirsty, the hand reaches for the watering can, and the soil was already saturated. Now you've drowned it faster. This is the single most common way a struggling plant becomes a dead one.
Run the time-of-day check. A plant wilting at 2pm in full sun and heat, standing back up on its own by evening, is just losing water through its leaves faster than the roots can supply it. That's normal under load. A plant still wilting at 7am, cool, no sun on it yet, with wet soil under the skewer, is not thirsty. The roots are not moving water. That's root damage, and more water is the exact wrong move.
Two more checks take ten seconds each. Smell the soil surface. Living soil smells like soil. Sour, swampy, or like rotten eggs means the air pockets are gone and anaerobic bacteria have taken over. Then tip the plant out of the pot into your hand. Healthy roots are white or tan, firm, and hold together when you tug. Rotted roots are brown, soft, and the outer sheath slides off between your fingers and leaves a bare thread behind. That test is definitive and it costs you nothing.
The Advice That Makes It Worse
A layer of gravel in the bottom of the pot for drainage. This is the most repeated piece of garden advice on earth and it is backwards. Water does not move from fine soil into coarse gravel until the fine soil above is fully saturated. It's called a perched water table. All you've done is make the pot shorter and move the soggy zone up closer to the roots. Skip the rocks. The only thing that drains a pot is a hole.
Repotting into something bigger to help a sad plant. You just read why that fails. More soil with the same small amount of root means wetter for longer. If roots are already rotting, a bigger pot accelerates the rot. When you repot a sick plant, go the same size or smaller, cut off the mush with clean scissors, and use fresh mix.
Garden soil or topsoil in a container. In the ground, that soil drains into more soil and roots and worms keep channels open in it. Packed into a bucket, the same soil collapses into a dense brick with no air in it. Container mixes are mostly bark, coir, peat and perlite for one reason, which is that they hold air after they hold water. Roots need oxygen. A soil that holds water and no air kills them politely over about three weeks.
And the last one. Just let it dry out completely. That's right for a mildly overwatered plant with live roots. It's wrong for one that has already lost half its root system, because it can't survive a hard dry swing either. That plant needs less water, less sun, fewer leaves to support, and time.
What to Do Before It Gets Dark Today
Skewer test in the middle of the pot. Write down whether it's wet at the bottom or dry at the bottom, because everything else depends on that one answer. Wet at the bottom, do not water. Dry at the bottom with a damp crust, water slowly in small amounts until it soaks in instead of running down the side, then let it drain.
Tip the pot and look at the hole. No hole, go make one. A drill, a nail and a hammer, a hot screwdriver, whatever you have. On a bucket, put several in the bottom and a couple more low on the side. Then empty the saucer and the pretty outer pot, and put the pot up on two bottle caps so the hole isn't sealed against the tray. That's a five minute fix that solves a shocking number of these.
If it smells sour, or it's limp at 7am, pull it out and look at the roots. Mushy and brown throughout, let it go. Some of them are already dead and hanging on out of spite, and you'll get further putting that effort into the next one than into a corpse. Some roots still white and firm, trim the rot, repot into fresh mix in a pot barely wider than the root ball, water once to settle it, then leave the damn thing alone in bright shade for two weeks.
Then stop watering by the calendar for good. The skewer decides, not the day of the week. Learn to read the pot instead of your own guilt and you stop replacing the same plant three springs in a row, you stop hauling home twenty dollars of doomed nursery stock every April, and you start eating something you actually grew on a back step. Keep guessing and you keep paying for the lesson without ever getting it.