Why are my Anthurium leaves turning yellow?

Start by reading the yellow

Before you change anything, look at which leaves are yellow and how they feel. Anthurium yellowing comes in patterns, and the pattern tells you the cause faster than any single symptom. Overwatering takes the lowest, oldest leaves first, and they feel soft and limp. Sun damage hits only the leaves facing the window, with bleached pale patches rather than a whole yellow leaf. A single bottom leaf yellowing slowly while everything above it thrives is just age. Crispy yellow with brown edges on a bone-dry pot is thirst, not drowning. Sorting by pattern keeps you from cutting back water when the plant actually needs more.

Why soggy soil is the usual culprit

Common indoor Anthuriums (Anthurium andraeanum, the flamingo flower, and the velvet-leaved Anthurium clarinervium) grow as epiphytes in the wild, clinging to tree bark with thick, fleshy roots that sit in open air and rainwater that drains away in minutes. Pot them in dense, water-retentive potting soil and those roots sit wet for days, the air pockets they depend on fill with water, and the roots suffocate and rot. A rotting root system cannot move water or nutrients up to the leaves, so even with plenty of moisture in the pot the foliage starves and yellows. That is the trap: the plant looks thirsty, you water more, and you make it worse.

You can confirm overwatering by the full picture. The lowest leaves yellow first and feel soft rather than crispy, the mix stays wet for many days after watering, drainage is poor or a saucer sits full underneath, and the base of the stem may feel soft. Tip the plant out of its pot and healthy roots are firm and pale; rotted ones are brown, mushy, and smell sour. Once you let the mix dry to the top inch and free up drainage, the yellowing should stop spreading, with healthy new growth following within two to four weeks. Because overwatered roots are the root issue here, the general principles in the Missouri Botanical Garden overwatering guide apply directly.

The other causes, ranked

These rank below overwatering but often overlap with it.

• Natural aging. A single old lower leaf yellowing slowly is normal. Only the bottommost leaf is affected while the rest, including new growth, look healthy.
• Too much direct sun. Harsh midday rays scorch the foliage. You see bleached, pale yellow patches on the leaves facing the window rather than even yellowing, and the velvet-leaved types like clarinervium burn especially fast.
• Underwatering. Prolonged drought stresses the roots. The mix is bone dry, it has pulled away from the pot, and yellowing comes with crispy brown edges.
• Fertilizer salt buildup. Too much feed leaves crusty salts in the mix that burn the roots. Lower leaves yellow with brown, scorched tips and a white crust on the soil surface.

A worked example

Say you have a flamingo flower on a north windowsill. Three lower leaves have gone yellow and soft over two weeks, the newest leaf looks fine, and when you poke a finger in, the mix two inches down is still wet from a watering five days ago. There is no drainage hole tray to empty, but the pot itself feels heavy. That combination, soft lower leaves plus wet mix plus slow drainage, is textbook overwatering, not sun (the north window is gentle) and not thirst (the soil is clearly wet). The fix is to stop watering, repot into a chunky aroid mix, trim the three spent leaves, and wait for the surface to dry before the next drink.

How to fix it

1. Check the soil. Feel the top inch of mix. If it is wet, hold off watering until it dries out.
2. Improve drainage. Repot into a chunky aroid mix with bark, perlite, and a little coco coir, make sure the pot drains freely, and empty any saucer so roots never sit in water.
3. Water when the top inch is dry. Use room-temperature water and soak until it drains from the bottom, then let the surface dry again before the next round.
4. Remove spent leaves. Cut fully yellow leaves at the base of the stalk with clean scissors.
5. Give bright indirect light. Set it near an east window or a few feet back from a brighter one, out of harsh direct sun.
6. Feed lightly during growth. In spring and summer feed at quarter strength every few weeks, and flush the pot occasionally to clear salt buildup.
7. Keep it warm. Hold the plant between 65 and 80F (18 to 27C) and away from cold drafts, heaters, and vents.