Does my houseplant have root rot?

Root rot is the most common way houseplants die in this part of Florida, and it is also the most misunderstood, because the word everybody uses for it points at the wrong thing. So let me start with what it actually is, since the definition is what makes the fix obvious.

What root rot really is

Two things are happening at once, and they feed each other.

The first is suffocation. Roots need oxygen the same way you do. Healthy potting mix is full of air spaces between its particles, and when you water, those spaces fill briefly and then drain. If the mix is dense, the pot is oversized, or the water cannot escape, the air spaces stay full and the roots begin to die from lack of oxygen alone.

The second is infection. Dead and dying root tissue in wet soil is exactly what water-mold pathogens like Pythium and Phytophthora are built to exploit. These are not true fungi; they are oomycetes, and they swim, producing motile spores that move through water films in saturated soil. That is why the wet conditions do not just weaken the plant, they actively transport the thing that finishes it.

Which brings us to the word. "Overwatering" makes it sound like a volume problem, as if you tipped too much water into the can. It almost never is. It is a frequency problem (watering again before the mix dried), a drainage problem (no hole, or a cachepot holding water), a pot-size problem (a small root system in a big pot leaves soil nothing is drinking from), and a light problem (a plant in dim light transpires slowly, so the pot stays wet for weeks). Fix those four and you can water generously and never see rot again.

The signs, ranked by how much they mean

• A stem that is soft or dark at the soil line. The most serious sign on the list. The rot has reached the crown, and the plant is on a clock.
• Soil still wet several days after watering, especially with a sour or swampy smell. The condition that produces everything else here.
• Yellowing leaves, usually from the bottom up, often with several going at once rather than one at a time.
• Wilting in wet soil. This is the one that fools people most. The plant looks thirsty, so it gets watered again, which makes it worse. Damaged roots cannot move water, so the leaves wilt while standing in plenty of it.
• Fungus gnats. Not a cause, but an excellent early warning. Their larvae need chronically wet organic topsoil, so a gnat problem is your soil telling on you before the roots do. See fungus gnats.
• Growth that has simply stopped for months in a season when the plant should be growing.

How to tell root rot from the things that look like it

Underwatering, hunger, and rot all yellow leaves and wilt plants, so do the checks in this order.

• Feel the soil two inches down before anything else. Wilting in dry soil that recovers within hours of a soak is underwatering. Wilting in wet soil is root failure.
• Take the plant out of the pot. This is not drastic and it does not hurt the plant. Tip it sideways, support the base, and slide the pot off. You will know within ten seconds.
• The sheath test. Pinch a root and pull gently. Firm and intact is healthy. If the outer layer slides off and leaves a thin thread behind, that root is gone.
• Smell it. Healthy potting mix smells like earth. Rot smells sour, swampy, or like a drain.
• Colour matters less than texture. Plenty of species have naturally tan or brown roots. Mushy is the diagnostic word, not brown.

What to do this week

1. Unpot the plant and rinse the root ball gently so you can actually see what you have.
2. Cut away every soft, dark, or slimy root with clean scissors, back to firm tissue. Sterilise the blades between plants.
3. Remove roughly as much top growth as you removed root, so the leaves that remain can be supported by the roots that remain.
4. Repot into fresh, chunky, fast-draining mix, in a clean pot with drainage holes, sized to the surviving roots. Do not size up: a big pot around a small root system is what caused this.
5. Water it in once, then let the mix approach dryness before watering again. Check with a finger, not a calendar.
6. Move it somewhere brighter, out of direct midday sun, so it can actually use the water it gets.
7. No fertilizer until it is visibly growing again. Damaged roots plus more salt in the soil is a second injury.

When to call a professional

Call if the stem is soft, if the plant matters to you and you would rather not gamble, or if this keeps happening across several plants: that last case is almost never the plants and almost always the pots, the light, or the routine, and it is exactly what one health diagnosis visit is designed to sort out. I will check the roots on everything in the house, tell you honestly which plants are recoverable, repot what needs repotting, and leave you a watering plan built around your actual light rather than a generic schedule. If a plant is past saving I will say so, and take a cutting from the healthy growth before we lose it entirely.

Related: snake plants going mushy at the base are usually this same story in a plant that hides it well, and fungus gnats are the early warning most people notice first.