|I have a large diffenbachia (sp?)that keeps drying at the leaf tips, then the leaf will turn a yellowish color and wilt. It is kept in an east window area and does not get any direct sun light. I have it in Miracle Grow soil. I tend to keep it damp. House temperature is generally 70 - 75?. It is putting off new leaves that are slightly deformed and the tips are brown.|
|There are several possible causes for yellowing, wilting and tip burn. It could be due to over or underwatering, overfertilizing, lack of humidity, or possibly a pest. Direct sun can also cause problems, so make sure the light angle has not changed enough as summer begins thus causing the plant to be in direct sun in the morning -- sometimes a spot that is shady in winter is sunny in summer.
If you are keeping the soil constantly wet, you may be overwatering it thus causing root problems that show as leaf symptoms. The soil should be moist but not wet. The soil surface should dry a bit between waterings and the container must have a drainage hole in the bottom to allow excess water to escape. If there is a saucer under the pot, be sure to empty it of any collected water. Be sure your water is soaking into the potting mix and not running out the sides between the soil and container, this could result in underwatering even though you are applying water often. Use tepid rather than cold water when you water it, cold water can shock the plant.
These plants like warm temperatures but with ample humidity. During the winter heating season the air in our homes tends to be very dry. Using a humidifier or setting the plant on a water and pebble tray can help. Use a shallow tray and fill it with pebbles, then add water to the top of the pebbles. Set the plant on the pebbles so the bottom of the container is just above the water level. Top up the water as it evaporates.
If your potting mix included a fertilizer, do not fertilize in addition until the time period for the initial fertilizer has passed. Then use a water soluble fertilizer at half the recommended strength and feed only when it is actively growing from spring to fall. This plant is sensitive to a buildup of salts in the soil such as from fertilizer, so you may need to leach the soil every few months. Water thoroughly to run off, then repeat one or two more times in quick succession.
New growth is sometimes distorted due to insects such as aphids or spider mites. Inspect the plant carefuly and if needed, treat with commercially formulated insecticidal soap per the label directions.
I hope this helps you trouble shoot.