Why are the leaves on my heartleaf philodendron turning yellow and brown?

What's likely going on

From the photo, the plant looks like a heartleaf philodendron with:

• Several older leaves turning solid yellow, some then going brown and crispy.
• Newer leaves higher up that are still a healthy green.

What we can see for sure:

• Yellowing is mostly on the lower, older leaves along long vines.
• The plant looks fairly full, not collapsing or rotting.

What’s most likely causing it:

1. Normal leaf aging, made worse by watering habits. Philodendron vines regularly shed their oldest leaves. If watering is a bit off (either too often or letting it get very dry), more of those older leaves yellow at once.
2. Possible overwatering / poor drainage. If the pot has no drainage holes or stays wet for many days, roots get stressed and older leaves turn uniform yellow, then drop.
3. Or occasional underwatering. If the soil gets bone-dry and leaves feel crispy and curled, that’s stress from drying out too hard between waterings.

Because this is happening to several plants, the common factor is usually the watering routine, not a disease.

What to do

1. Check the pot and soil.
   • Make sure there’s a drainage hole.
   • Stick a finger 3–5 cm into the soil before watering. If it’s still quite moist, wait.
2. Adjust watering.
   • For philodendrons, water thoroughly only when the top 3–5 cm are dry.
   • Empty any water that collects in the saucer after 10–15 minutes.
3. Assess roots if yellowing is heavy.
   • Slide the plant out of the pot. Healthy roots are mostly white or light tan and firm.
   • If many roots are brown, mushy, and smell bad, trim those and repot in fresh, well‑draining mix.
4. Give it good light.
   • Bright, indirect light (near a window but not harsh midday sun) helps the plant replace old leaves quickly.
5. Remove damaged leaves.
   • Snip fully yellow or brown leaves at the base of their stem. They won’t turn green again.

How to prevent it

• Keep a simple schedule: check soil every few days, water only when the top has dried, not by the calendar.
• Use a loose mix (potting soil + perlite or coco chips) so extra water can drain.
• Avoid letting the plant sit right in the path of very dry air from heaters or fans, which speeds up leaf loss.
• Once or twice a year, check if it’s root‑bound and move up one pot size if roots are circling tightly.

When to worry

• Many leaves (including new ones) turn yellow at once, feel soft, and stems look mushy – that points to serious overwatering or root rot.
• New growth is stunted, pale, or deformed.
• You notice a bad smell from the soil.

If any of these show up, act quickly: unpot, trim bad roots, repot in fresh mix, and water much less often until it recovers.