What Makes the Lower Leaves on a Caladium Turn Yellow and Die?

Moisture

• Caladiums do not do well in dry climates. Even in humid regions they like a continuous supply of water. If they don't get enough water, the leaves will turn yellow and droop. If they don't get water soon, the plants will go dormant. Revive caladiums by giving them enough water to moisten the soil. Too much water can lead to root rot, a common problem in caladiums.

Root Rot

• Many caladium cultivars are susceptible to root rot. It is caused by Pythium myriotylum, a soilborne fungal pathogen, that infects the roots of the plants, causing yellowing of leaves, leaf droop and eventually killing the plants. It is brought on by over-watering. Caladiums like soil that is continually moist, but it should not be so wet that water pools. Try some of the more resistant cultivars, including "Frieda Hemple," "Candidum" and "White Christmas."

Sunlight

• Moving plants from shade to full sun abruptly will scorch the leaves. Scorching can appear as yellowing. In houseplants it will appear on the leaves closest to the window. To correct this, remove scorched leaves and move the plants from shade to direct sun, or brighter intensity light, gradually. Though some cultivars have been bred for direct sun, most caladiums only produce their best colors in shade.

Cold

• Caladiums are native to Brazil and prefer higher temperatures. When nighttime temperatures dip below 60 degrees Fahrenheit, this can cause yellowing and drooping in the leaves as the plants enter dormancy. Air conditioning can have the same effect. For outdoor plants, you can extend the growing season by covering them at night to trap heat around the plants. For indoors plants, move them away from air-conditioning vents.

Bacterial Disease

• Xanthomonas leaf spot, a bacterial infection, starts on the underside of the leaf margin. It appears as a small, water-soaked spot that eventually becomes yellow or tan. High humidity encourages growth of the disease, spreading it across the leaf. Older leaves and petioles will turn yellow, droop and die. Removing infected leaves usually cures the problem. Do not water from overhead, and disinfect garden tools you use on the plant.

End of Season

• Because caladiums are tropical plants, and do not tolerate temperatures below 60 F, as summer ends, the leaves will yellow and droop indicating it’s time to dig them up. Store the tubers in an area where the temperature will not fall below 70 F. In USDA zones 9 through 11, tubers can be left in the ground.