Yellow leaves on Rex begonia most often point to a watering problem. On this plant, the first signs are often yellowing leaves and mushy rhizome. Check the causes below to find which one fits, then follow its fix.
Thirst (underwatering). Water thoroughly (every 6 to 8 days in summer is the usual pace for a Rex begonia), then settle into feeling the soil before every watering rather than watering on a fixed day.
How to tell
The yellowing comes with pale, stretched new growth leaning toward the nearest window. That combination shows that the spot is too dim for Rex begonia.
The fix
Move it to a brighter spot, but keep it out of harsh midday sun, which scorches.
How to tell
The soil is still wet days after watering, the lower and oldest leaves yellow first, and the stem base may feel soft.
The fix
Stop watering. Make sure the pot can actually drain, and wait until the top 3 cm of soil feel dry to the touch. If the base is mushy or smells sour, unpot it and trim any brown, soft roots before repotting in fresh mix.
How to tell
Older leaves fade to an even pale yellow and growth has clearly slowed. On a plant that likes 50–70 % humidity and regular water, this shows up after many months in the same tired mix once feeding has lapsed.
The fix
Feed with a balanced, diluted liquid fertilizer through the growing season, and refresh the top layer or repot if it’s been over a year.
How to tell
A single bottom leaf slowly yellows while the rest of the plant looks healthy and is pushing new growth.
The fix
Nothing is wrong. Snip the spent leaf off and carry on. Plants retire their oldest leaves.
Check the mix regularly so it never goes bone dry for long, keep humidity up, and give it bright, indirect light.
Same genus or the same care pattern.
Last reviewed: 2026-08-26
