The water needs of indoor plants change in the winter months. Most people are concerned with the frequency of application and the amount of water used but there is another important factor about water quality -- softened water.
Regular tap water is described as hard because it contains a variety of dissolved minerals. Water softeners swap the harmless calcium and magnesium in hard water of sodium. But sodium can present problems to both the plant and growing medium.
First, sodium ions tend to break down the soil structure,. Which results in poor physical condition of the mineral around the root system. When this occurs, the potting material no longer drains well and root problems can develop.
Second, sodium can accumulate in the plant. If the plant takes enough of the materials from the soil, it may die. Sodium uptake is more of a problem where there is little or no leaching (flushing) of the soil mix after each watering.
If you do use softened water on your indoor plants, it's important to use enough water at each watering to leach the soil around the root system. The leaching process is even better if you periodically can use the rain water or unsoftened water. In the event that leaching has not been done and the plants are in poor quality it may be helpful to repot the plants with fresh potting soil.
Another question that comes up about this time of year concerns the popular spider plant or Chlorophytum. This plant is generally used in hanging baskets. It has long slender leaves that are white along the mid-rib and green along the margin,. Under the proper growing conditions, these plants will send out a long, leafless stem that produces a small plant at its tip.
If growing conditions are wrong, the plant may fail to produce these interesting and attractive runners, or new plants. Various incorrect suggestions have been offered over the years concerning the cause of poor performance of these plants indoors. Some suggestions include: `Your plants must touch in order to produce baby plants,` `The plants must be pot-bound to form young plants,` or `The sex of the parent plant determines the plant's ability to form the runners and baby spider plantlets.`
In reality, the ability of Chlorophytum to have runners and subsequent plantlets is a photoperiodic process governed by the amount of light the plant receives. If the hanging spider plant is located where artificial light sources extend the day length beyond 8 hours, you'll have a vegetative plant with no runner production. Keep the plant I a room that has no night lights, and the plants will eventually send out runner and new plantlets. Freezing outdoor temperatures can be very hard on house plants, especially if the foliage comes in contact with the window pane. It is not uncommon for the glass to be cold enough to actually freeze the leaves and stems of plants. Unfortunately, we have had weather cold enough lately to cause these injuries.
The alternate freezing and thawing of the soil during winter months is more harmful to plants than the continued cold and frozen conditions.
Freezing and thawing of the soil has a tendency to heave plants out of the ground. Many times small feeder roots are torn off as the plants move up and down in the soil.
But this damage can be prevented if you mulch the plants as soon as the soil becomes frozen. The mulch won't keep the soil warm as some people think -- but it keeps it in a frozen states and prevents the alternate freezing and thawing.
It's particularly important to mulch shallow-rooted plants with sawdust, peat moss, oak leaves, evergreen boughs or any other material that won't pack down with time.
Greg Solt is a Penn State Cooperative Extension Agent in Northampton County. Lawn and Garden assistance is available from Penn State Master Gardeners, Northampton County Cooperative Extension, Greystone Building, Gracedale Complex, Nazareth, PA 18064-9212; 610/746-1970.