Chinese Evergreens Rotting Leaves - Knowledgebase Question

Washington, DC
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Question by ricksma
December 30, 1997
I purchased two very large pots of Chinese Evergreen. There about 10-12 plants in each pot,leaves are 12-15" long, and I have repotted each in 15" pots. I have installed recessed spot lights in the ceiling 8-10' above these plants using regular 50 watt bulbs and supplemented by filtered northern natural light. One plant is doing quite well after 4 months, with very little extra attention and is beginning to send up healthy new growth. The other is sending new growth too, but many have a black and rotted looking tip even before opening, others have a white verticle strips of something that might be powdery mildew (but definetly NOT mealy bug), and even further, there is a shiny, stickey-to-the-touch substance on many leaves as well. Also, some of the outer leaf stalks are showing yellow. I have begun to water this pot (the most recent 2 waterings at 2-3 week intervals) with a mixture of 1 tsp of liquid detergent to a gallon of water. Additionally, I have washed the leaves individually with a mild soap and water bath. The pots are too heavy for me to be able to take to the tub for showers.

Answer from NGA
December 30, 1997
Though I am sure you already know this stuff, let's go over the cultural requirements for Chinese Evergreen (Aglaonema) just so you can make sure everything is OK there. Sometimes if any one of these is off, chaos ensues! They like the temperature to be on the warm side in the summer and a minimum of 60F in the winter. Your lighting should be in the range of semi-shaded to bright. Plants should however be kept away from bright sunlight. In the winter, water very sparingly - during the rest of the year, keep soil moist. One very important factor is air humidity, moist air for the Chinese Evergreen is a must. One of the symptoms of air which is too dry is brown to brownish black tips on the leaves. On the other hand, rotting at the tips can be a sign of too much humidity or more commonly, overwatering. The slimey-sticky stuff you describe on the leaves also sounds like overwatering. Is there any of that substance on the pot? Leaves should be misted regularly with a very fine mist. It is important to use a fine mist because water left to stand on the leaves can also cause rot. Interestingly enough, these plants also don't do well in areas that have smoke from cigarettes or a fire place. They are also not fond of drafts of any kind. The leaves that are yellowed...are they leaves toward the top or the bottom? If near the top are they still firm? I ask because if they are firm and yellow and are on the upper part of the plant one of the problems could be a calcium deficiency. If the yellowed leaves are at the bottom portion of the plant, once again, the culprit is most likely overwatering or exposure to drafts. Now for the white vertical strips of the mildew like substance. You are probably right, it is probably powdery mildew. This isn't fatal. Simply remove the mildewed leaves. You can stop the disease from coming back by improving air circulation around plants and cutting back on watering a bit. For the slimy leaves, wipe them down with a cotton ball saturated with rubbing alcohol. Wipe off any excess. Check your soil. If you see any mold or mildew growing there, repot if feasible with fresh soil. If not feasible, remove the mildewed spots with a spoon. Be sure when you water the plant that you empty the overflow saucer. Stop watering with the soap solution--you may be damaging the roots. Good Luck!

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