ใบเหลืองหน้าฝน 5 สาเหตุรากเน่า วิธีแก้ด่วน 2026

Yellow leaves in the rainy season are most often caused by root rot, which happens when soil stays soggy so long that roots cannot breathe, and soil fungi such as Pythium and Phytophthora attack them. Not every yellow leaf means root rot, but if you see yellowing, wet soil, and soft brown roots, unpot the plant and check the roots right away. The longer you wait, the more likely you are to lose your favorite plant.

Have you ever woken up, opened the curtains in your condo, and seen rain pouring all night, then noticed a couple of yellow leaves on the plant sitting on your bookshelf? Your heart sinks. I see this every rainy season. Customers send photos asking if it is a lack of fertilizer, when the plant simply got too much water.

Are Yellow Leaves in the Rainy Season Always Root Rot?

Not always. Yellow leaves are a symptom, not a disease. Plants send the same signal for many reasons, including lower light in the rainy season, natural aging of old leaves, or nutrient deficiency. The easiest way to tell is to check the soil and the roots.

Symptom	Most likely cause
Many leaves yellow at once, wet soil, musty smell	Root rot from waterlogging
Lower leaves yellow one at a time, soil dries normally	Natural aging of old leaves
Pale leaves overall, slow growth, soil dries well	Low light or nutrient deficiency
Yellow and wilting leaves although soil is wet	Damaged roots that cannot absorb water

5 Most Common Causes of Root Rot in the Rainy Season

1. Watering again while the soil is still moist

In the rainy season the air is humid and soil dries much slower than in summer. A pot that was watered twice a week before may now need water only once a week or even less. Poke a finger about 2-3 centimeters into the soil. If it is still cool and damp, do not water yet.

2. Compacted soil with poor drainage

Cheap ready-mixed soil made only of peat moss or loam collapses after frequent watering and holds water for a long time, so roots get no air. Most indoor plants like an airy mix. Add perlite, pine bark, or volcanic rock to help water drain faster.

3. Pots with no drainage hole, or a clogged hole

Pretty ceramic pots with no holes are where I see root rot start most often. Water pools at the bottom where you cannot see it. Another thing people forget is the saucer. If you leave water in it after watering or rain, the roots keep sitting in water.

4. A pot that is too big for the plant

When a small plant is moved into a much larger pot, the extra soil holds water the roots cannot use in time. Choose a pot only about 1-2 inches larger than the old one.

5. Keeping plants in damp spots with no airflow

Balconies hit by rain splash or closed-off corners of a room make soil dry slowly and let fungi build up. Plants I often see with this problem include golden pothos, monstera, rubber plant, and succulents left in direct rain.

First Aid for Root Rot: Step by Step

Stop watering immediately and remove the saucer
Gently slide the plant out of its pot and shake off as much old soil as you can
Rinse the roots with clean water and check the color. Firm white or cream roots are healthy. Dark brown, mushy, smelly roots are rotten
Use clean scissors wiped with alcohol and cut away all rotten roots until you reach healthy tissue
Trim some of the yellow or damaged leaves to reduce the load on the remaining roots
Let the roots air dry in a shaded, breezy spot for about 1-2 hours so the cuts dry
Repot in an airy, fast-draining mix in a pot with drainage holes
Place in bright indirect light with good airflow, wait about 5-7 days, then water lightly. Do not fertilize until new leaves appear

A myth I have to correct plainly: feeding fertilizer to rescue a plant with yellow leaves from root rot only makes things worse. Fertilizer burns roots that are already hurt. Wait until the plant recovers first.

Preventing Root Rot All Rainy Season in Small Spaces

Lift pots off the floor or saucer with pot feet so water can actually drain
Move rain-soaked plants under an eave or near a window with light and airflow
Check the soil with a finger or a wooden stick before every watering. Do not water by the calendar
Use a plastic pot with holes inside a ceramic cover pot, so you can lift it out to water and pour away excess
If you have dogs or cats, be careful with strong fungicides or chemicals within their reach, and keep plants on high shelves for now

If a plant at home is too far gone, do not be sad. You can often take cuttings from healthy stems or tips of plants such as golden pothos or monstera. And if you want a fresh start with a healthy one, we select and pack our plants carefully to reach your home. Come adopt one to heal your heart at your condo. 🌱

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Can a plant with root rot be saved?

Yes, if some firm white or cream roots remain. Cut off all rotten roots, let the cuts dry, then repot in a fresh airy mix and wait 5-7 days before watering. If all the roots are rotten, the chance of survival is very low, so take cuttings from the healthy parts instead.

Should I cut off yellow leaves?

You can. A fully yellow leaf will not turn green again, and removing it stops the plant spending energy on damaged foliage. Cut only as needed, a little at a time, and do not strip the plant bare.

How often should I water indoor plants in the rainy season?

Water only when the soil is dry about 2-3 centimeters deep. Plants in air-conditioned rooms or condos often dry out slower in the rainy season, so every 7-10 days may be enough. Do not water by fixed dates. Go by the real moisture in the soil.

Can fungicide prevent root rot?

It can help in some cases, but it is not the main fix. If you overwater and the soil drains poorly, fungicide cannot save the plant. Fix the root causes first, which are water, soil, and pot, then consider fungicide carefully according to the label.