DATE:      1/4/01
WRITERS:   Meg R. Williamson, (864) 656-7506, diagnostician, 
           Clemson University Plant Problem Clinic
           Bob Polomski, (864) 656-2604, Clemson Extension 
           consumer horticulturist                
EDITOR:    Giles Singleton, (864) 656-3876

                                   WWW.CLEMSON.EDU/PSAMEDIA

Winter cures for ailing houseplants

     CLEMSON -- Are your houseplants dropping leaves, turning 
yellow, getting spots, wilting or dying? If so, here are ways 
to diagnose the problems and nurse them back to health.
     You may want to blame these maladies on a plant disease, 
but organisms that cause plant diseases do not commonly infect 
interior plants. Inside, the humidity is usually too low, and 
there is no rainfall or wind to spread the organisms from one 
leaf or plant to another. In addition, potting mixes are 
essentially sterile, unless outdoor soil has been added.
    Instead of looking for diseases, check for insects and mites, 
which commonly infest indoor plants. If these can be ruled out, 
and you have used a sterile potting mix, what could be damaging 
your plants? Environmental or cultural conditions are probably 
to blame.  
      Following are some conditions that can cause problems, 
the symptoms they cause and ways to bring the plants back to 
health.
     Humidity in houses is generally fairly low, and it decreases
further during winter when the heat is on. Many foliage plants 
perform best under high humidity levels, so low humidity can cause 
leaf tips to dry out and turn brown.
     Some ways to increase humidity are:
       · Group plants together, so water lost by leaves and 
         potting mix moistens the air for all;
       · Use a room humidifier or cool-mist vaporizer (this 
         raises the comfort level for people too);
       · Set pans of water on wood stoves or radiators;
       · Place plants that love high humidity on a pebble-filled
         tray of water inside an aquarium tank with an adjustable
         opening at the top. 
     Inadequate water is another common problem with indoor 
plants. When the soil dries out, plants wilt and leaf margins 
may turn brown. Yellowing and dropping of leaves are other symptoms
of inadequate water.
     To help plants with these symptoms, water them thoroughly 
when the top half-inch of soil is dry.     
     Keep in mind that symptoms of overwatering are similar to 
those caused by inadequate water, because roots in waterlogged 
soil function poorly. So if your plant is yellowing or wilting, 
or if the leaf edges have turned brown, check the soil moisture 
level before assuming that it is dry.
     In winter, when light levels are low and temperatures are 
cool, plants use less water. If you continue watering as if it 
were summer, you are probably overwatering. Poorly drained soil 
or pots can also result in overwatering. 
     Overwatering can also cause a soft rot of stems at the soil 
line. This symptom is especially common with cacti and other succulents.
     Succulent plants fare better in dry air and soil conditions.
However, these plants generally need higher levels of light than 
those present in most homes.
     Excess nutrients or other minerals can cause leaf damage. 
Fluoride toxicity is the most common of these problems. Many 
foliage plants are sensitive to fluoride and react adversely 
to our fluoridated water. Symptoms include brown or yellow leaf 
spots and dry, brown leaf tips or margins.
     Bottled spring water or distilled water can be purchased 
and used to water susceptible plants. Alternatively, tap water 
can be filtered to remove much of the fluoride.
     If you want more information on this topic, look for 
"Foliage Plants for the Interior," a Clemson Extension publication 
by Al Pertuit (EC688, cost $8.50). This can be obtained at
http://cufan.clemson.edu/olos/ or from your county's Clemson 
Extension office (locations and numbers at http://www.clemson.edu/extension/ ).  
                     **********************
     If you have gardening questions or comments, write to PSA 
Media Relations, A-101 Poole Agricultural Center, Clemson 
University, Clemson, S.C. 29634-0129. You might also want to 
check out our website at http://www.clemson.edu/psamedia.
                             END