First, check the soil. Push a finger 2 to 3 cm (0.8–1.2 in) into it and lift the pot. Dry and light means thirst. Wet and heavy means too much water or poor drainage.
Most likely cause
Overwatering & early root rot
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.
Small dark flies around moist potting medium may be fungus gnats.
The fix
1
Stop watering.
2
Make sure the pot can actually drain, and wait until the top 3 cm (1.2 in) of soil feel dry to the touch.
3
If the base is mushy or smells sour, unpot it and trim any brown, soft roots before repotting in fresh mix.
More about this
They suggest conditions suitable for breeding, without proving that the surface never dries.
Other possible causes
Not a match? Compare the signs below to find the one you have.
Thirst (underwatering)
The soil is bone dry, and the yellowing arrives alongside curling leaves rather than soft, mushy growth.
The fix
1
If the soil is dry, water thoroughly (every 6 to 8 days in summer is the usual pace for a ti plant), then settle into feeling the soil before every watering rather than watering on a fixed day.
Too little light
The yellowing comes with pale, stretched new growth leaning toward the nearest window.
The fix
1
Move it to a brighter spot, but keep it out of harsh midday sun, which scorches.
More about this
That combination shows that the spot is too dim for a ti plant.
Hungry (nutrient shortfall)
Older leaves fade to an even pale yellow and growth has clearly slowed, usually after many months in the same tired mix.
The fix
1
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.
Normal lower-leaf shedding
A single lower leaf yellows and drops while the top keeps pushing new growth.
The fix
1
Nothing is wrong.
2
Snip the spent leaf off cleanly at the stem and carry on.
More about this
Ti plant naturally sheds its oldest leaves as the cane grows taller.