Why are my Monstera leaves turning yellow?

Why overwatering is the usual culprit

Monstera deliciosa is a climbing aroid from the forest floor and trunks of Central American jungles. Its thick, fleshy roots evolved to grip bark and breathe in open air, so they need oxygen around them and rot quickly when left in saturated mix. This is why a Monstera shrugs off the occasional dry spell but suffers fast in constant wet.

Overwatering rarely means watering too often by the calendar. More often it means the soil cannot dry between waterings: a dense peat-heavy mix, a pot with no drainage hole, a saucer left full, or a pot far too large for the root ball. When roots sit in airless mud they suffocate and begin to die, and dying roots cannot move water or nutrients up to the leaves. The plant responds by yellowing its oldest, lowest leaves first.

You can confirm overwatering by the pattern. The yellowing starts on the bottom leaves and works upward, the affected leaves feel soft and limp rather than crispy, the soil is still damp several days after watering, and overall growth has slowed or stopped. A sour, swampy smell from the soil is a strong sign roots have already begun to rot. Missouri Botanical Garden's guidance on overwatering describes how waterlogged soil drives out oxygen and leads to the root damage that shows up as yellow, wilting leaves.

Reading the yellowing pattern

The position and feel of the yellow leaves tells you which cause you are dealing with.

• Soft yellow lower leaves, wet soil. Overwatering and likely early root rot. The most common case.
• A single oldest leaf yellowing slowly. Natural aging. As a Monstera climbs and grows it sheds its bottommost leaf now and then. If only one is affected and new growth looks healthy, no action is needed.
• Pale, even yellowing with leggy, small new leaves. Too little light. The plant cannot photosynthesize enough to feed itself, so it cannibalizes older leaves.
• Yellowing with crispy brown edges and bone-dry soil. Underwatering. The soil has pulled away from the pot wall and water runs straight through without soaking in.
• Broad, even paling with smaller, lighter new leaves. Possible nutrient shortage in old, spent soil that has not been fed or refreshed in a year or more.

A worked example

You have a Monstera in a 10-inch pot with no drainage hole, in a low-light hallway. The two lowest leaves have gone soft and yellow over a week, the soil is still wet from a watering five days ago, and there is a faint sour smell. Three signals line up: wet soil, soft lower-leaf yellowing, and a pot that cannot drain. This is overwatering with the start of root rot. The fix is to unpot, trim any brown mushy roots, repot into a chunky aroid mix in a pot with drainage, and water far less until the plant recovers. Move it brighter while you are at it so it can dry faster between drinks.

How to fix it

1. Check the soil. Feel the top 1 to 2 inches. If it is wet, hold off watering until it dries out.
2. Improve drainage. Use a chunky aroid mix of bark, perlite, and potting soil, make sure the pot has a drainage hole, and empty any saucer so roots never sit in water.
3. Water by need, not schedule. Water only when the top 1 to 2 inches are dry, then soak until it drains from the bottom.
4. Brighten the spot. Move it to bright indirect light beside an east window or 2 to 4 feet from a south or west one.
5. Remove spent leaves. Cut fully yellow leaves at the base of the petiole with clean shears; the green will not return.
6. Feed during growth. In spring and summer feed at quarter to half strength every 2 to 4 weeks if the soil is old.
7. Check the roots. If many leaves yellow and the soil smells sour, unpot and trim any mushy brown roots, then repot in fresh mix.