An unhealthy houseplant shows it through yellow, brown, limp or falling leaves, through growth that slows down or through pests. The most common cause is watering: too much of it, more often than too little. Light, dry air and cold come next.
Always start with the soil: soggy for a long time, it points to overwatering; dry and crumbly, to underwatering. A problem that affects the whole plant almost always comes from its growing conditions, whereas a disease starts on a few leaves.
Sick plant: which cause matches the symptoms?
| What you see | Most likely cause | First step |
|---|---|---|
| Old and new leaves turning yellow and dropping at the same time, damp soil | overwatering | let the soil dry out and check the roots |
| Lower leaves turning yellow first, dry and brittle edges, dry soil | underwatering | water thoroughly, then keep an eye on the soil |
| Brown tips and edges, leaves curling up | air that's too dry | move it away from the heater |
| Dry brown patches on leaves exposed to the sun | sunburn | shield it from direct sun |
| Long, spindly stems, pale leaves | low light | move it closer to a window |
| Leaves turning black after a cold snap | cold | keep it away from doors and windows that open |
| Sticky leaves, tiny insects or white cottony clumps | pests | isolate it from your other plants |
| Gray fuzz or white powder on the leaves | a fungal disease | remove the affected leaves |
1. Yellow leaves
Yellow leaves are one of the most common symptoms. They can have several causes:
- overwatering
- low light
- nutrient deficiency
- stress from a change of environment
Look at which leaves are turning yellow. When old and new leaves yellow at the same time, think overwatering; when the lower leaves go first, think underwatering or low light. On a yucca, though, the lower leaves yellow and drop one by one as the trunk grows, and that's normal. The context (watering frequency, season, recent move) then helps you decide: a ficus, for example, often drops its leaves after a simple move. If you suspect overwatering, our article on the signs of an overwatered plant explains how to save it.
💡 Not sure about the symptoms? Arroseo+'s health diagnosis guides you. You describe what you see, with a photo if you like: the app points to a probable cause (disease, pest or deficiency) and lists the steps to take. This diagnosis remains a starting point, not an expert opinion. Download the app
2. Brown leaves
Brown edges can indicate:
- air that's too dry
- underwatering
- too much fertilizer
- sunburn
Where the brown appears points to the cause: dry, brittle edges suggest underwatering or dry air, brown patches in the middle of the leaf rather overwatering. Some tropical plants, like the monstera or the calathea, are particularly sensitive to air humidity.
3. Limp or drooping leaves
A drooping plant often lacks water or light, or has damaged roots. The peace lily, for example, droops when its soil dries out, then perks back up after watering. If a plant wilts while its soil is damp, its roots are probably suffering from overwatering. Check the soil before watering more: watering by reflex is precisely the most common beginner mistake, as our article on the ideal watering frequency explains.
4. Slowed growth
A plant that stops growing may lack light, nutrients or room for its roots. Long, spindly stems and pale leaves point to low light; dull growth in a plant repotted long ago, to worn-out soil. Repotting is sometimes enough to get it growing again.
5. The presence of pests
Some pests are very common indoors: scale insects and mealybugs, spider mites, aphids, fungus gnats.
The first signs to look for:
- small spots on the foliage
- sticky leaves
- insects visible under the leaves
- white cottony clumps where the leaves meet the stem
These pests often take advantage of the outdoor-to-indoor move in the fall to settle in discreetly. If you have just brought your plants in before the cold, an inspection over the following weeks lets you spot an infestation before it spreads.
6. Diseases: mold and leaf spots
Grayish-brown fuzz on leaves or stems signals gray mold, and a white powder signals powdery mildew: two fungal diseases that thrive in humidity. Dry spots with concentric rings are also fungal; dark, wet-looking spots with angular edges point to bacteria.
Remove the affected leaves. A fungicide can treat a fungal disease, but there is no treatment for a bacterial or viral disease: in that case, it's better to part with the plant.
How do you treat a sick houseplant?
- check the soil and the roots: white, firm roots are healthy, brown or black, mushy roots are rotten
- fix the cause: watering, light, temperature or air humidity
- remove leaves that are completely yellow, brown or moldy, and keep those that are still mostly green
- isolate a plant that has pests
- repot it in fresh soil if its own is soggy or worn out
A plant can bounce back as long as it still has healthy roots. Some, like the poinsettia or the cyclamen, are short-lived indoors: their decline isn't necessarily a disease.
Why diagnosing quickly matters
The earlier a problem is identified, the better the plant's chances of recovering. Many people make things worse by adding even more water, when the problem is actually caused by overwatering in the first place.
Frequently asked questions
How can you tell if a plant is sick?
Look at its leaves (yellow, brown, limp or falling), its growth and the undersides of the leaves, then touch the soil. A problem that affects the whole plant usually comes from watering or light; spots on a few leaves suggest a disease.
What do yellow leaves on a houseplant mean?
Yellow leaves can be due to overwatering, low light, a nutrient deficiency or stress from a change of environment. Context is essential to identifying the exact cause.
Why are my plant's leaves turning brown at the edges?
Brown edges often indicate air that's too dry, underwatering, too much fertilizer or sunburn.
What are the most common houseplant pests?
Mealybugs, spider mites, aphids and fungus gnats are the most common. Small spots, sticky leaves and visible insects under the leaves are the first signs to spot.
How can you identify a plant disease from a photo?
With a diagnosis app. Arroseo+'s works like this: you describe what you see, with a photo if you like, and the app suggests a likely cause. It's a lead, not an expert opinion: always check the soil and the roots.
How can you tell if a plant is still alive?
Take it out of its pot and look at the roots: if some are still white and firm, it can bounce back. If they're all brown, mushy and foul-smelling, the chances of saving it are very slim.
Why should you diagnose a plant problem quickly?
The earlier a problem is identified, the better the plant's chances of recovering. Conversely, adding even more water when the issue is actually overwatering often only makes things worse.
Worried about one of your plants?
Describe what you see to the Arroseo+ health diagnosis, with a photo if you like: the app points you to a likely cause and the steps to take. And against the leading cause of decline, overwatering, Arroseo reminds you to water each plant on its own schedule.
Download the app
