House Plant Tips

3/6/00
As we get closer to spring, your over-wintered house plants may not look as good as they did last fall. There are several indoor conditions and management practices that can take a toll on house plant quality.

Root rot is probably the most common plant problem indoors and is associated with overwatering. Heavy soils that drain slowly, as well as growing containers without drain holes lead to the problem. Repot into a container with holes in the bottom using a light-textured growing medium to correct this problem.

Nutrient deficiencies can occur and appear as light or pale green foliage. This is an indication of low nitrogen levels. Phosphorus deficiency is difficult to determine in house plants. Low potash levels may cause browning and dying of the leaf margins. Fertilizer applications every one to two months during the growing season, according to product directions, should reduce the risk of nutrient deficiency.

During the winter months, hot and/or dry indoor air will lower the humidity which results in wilting and dried stems and leaves. Group plants together or place them in shallow, pebble-filled trays that are filled with water. Keep the water level just below the surface of the pebbles to prevent a saturated root system that results in root rot.

Low winter light levels will also result in off-color or light yellow foliage. In low light winter growth may also be spindly and leggy. Supplemental light generally helps to control this problem as will locating the plants near a bright window.

The accumulation of unused minerals from fertilizer and hard water in the growing medium will cause root problems over winter. Mineral salts often appear as a white or yellowish crust on the soil surface and plant stems. This materials can be toxic to both roots and stems. Leaching the growing medium at monthly levels during the entire year will help to keep salts from causing problems. Leaching is accomplished when about 10 percent of applied water passes through the drain holes in the container. Discard any water that comes through the drain holes.

Pot bound roots will also reduce the quality of the foliage. If you remove the plant from the pot and note a large amount of roots circling the potting soil, repotting is necessary. The new pot should be several inches wider and deeper than the old one. It is not recommended to move the plant into a much larger pot. Excess root growth in a larger pot may reduce the quality of the stems and foliage.

With close attention to watering practice and the movement of house plants into better light and warmer temperatures of the spring and summer you will be able to return them to good health in a few weeks.

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**Dr. Robert Nuss is a horticulturist at Penn State. He coordinates all extension horticulture programs. He has bachelor’s, master’s, and doctoral degrees in ornamental horticulture and has been on the Penn State faculty since 1966.