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House Plant Trouble Signs

Wilting or partial wilting will often be the result of improper water relations in the plant. If sudden wilting is diagnosed, check the roots, pot or soil for the trouble. Some common causes are a lack of water, excess water, root rot, too much fertilizer and/or a salt buildup. Check the cause by pressing your finger, up to the first knuckle, into the soil. If the soil is dry to this depth, the plant needs water. If the soil is wet, too much water in the root area may be the problem. The roots may be saturated or rotting and incapable of absorbing water from the soil and supplying it to the leaves. Overwatered plants should be repotted into fresh soil. (Refer to the section on yellowing and death of all leaves and poor growth for more information on root rot.)

Plants which are pot bound may wilt because the roots are strangling each other. Don't be afraid to remove the plant from the pot and examine the roots to see if they are too dry, too wet or diseased. To remove, merely invert the plant and lightly tap the edge of the container on a solid object while holding the plant and soil ball (Figure 2). You may find the soil mass is completely enveloped in roots and the plant needs repotting.

Figure 2. Removing plant from container.

Sudden loss of leaves is frequently caused by a rapid temperature change. It may also be caused by such factors as prolonged hot or cold drafts, dry air, exposure to gas or furnace fumes or by changing the location of the plant from a sunny to a dark location. Ficus benjamina, commonly called weeping fig, frequently has sudden leaf drop when moved to a location with lower light intensity.

Yellowing or death of leaves may indicate a nutrient deficiency, usually nitrogen or iron. First apply a nitrogen fertilizer. If the foliage does not appear greener after three to four days, do not add additional nitrogen. Instead apply a chelated iron product. Iron is essential to healthy green leaves and may be present in the soil but in a form which the plant cannot use. Chelated iron is in a form which is readily available to the plant roots.

The yellowing and death of lower leaves may occur if plants become pot bound because of extensive root development. Rubber plant, Dracena, Diffenbachia and other woody plants are especially prone to this problem. When the lower leaves first start to yellow, apply extra nitrogen fertilizer or consider repotting. Occasional lower leaf drop may be normal. The length of time a plant will hold its leaves varies from species to species.

Yellowing of all leaves and poor growth may be due to excessive soil moisture and/or to root rot. If the drainage hole in the pot or plant box is plugged or if the plants constantly stand in water, the soil will be waterlogged and lack sufficient oxygen.

If a root rot problem is suspected, remove the rootball and check the roots. Healthy roots and root tips will be white or cream-colored. Rotted roots are a brown-black color and may appear slimy. Severely rotted roots may be hollow and easily broken between the thumb and index fingers.

Destruction of the roots by soilborne fungi and nematodes may cause a yellowing of the entire plant. Severe infestations of mites, aphids and scale insects, fertilizer burn, improper light and temperature, or improper pH all may cause plant yellowing. Soil pH prefers to the acidity or alkalinity of a soil measured on a scale of one to 14 with seven being neutral. Anything below seven is acid and anything above seven is alkaline.

Some plants such as the Norfolk island pine and Boston fern require an acid soil medium. This can be achieved by using a potting mixture high in peat and by using an acid fertilizer. Acid fertilizers help to reduce the pH of the soil. Most North Dakota well and river water is alkaline, so regular use of an acidifying fertilizer would be advantageous to plant growth .

Finely specked leaves with a faint mottled, lighter color may be infested with spider mites. When the mites are plentiful, the upper and sometimes the lower surface of the leaves may appear dusty due to their webbing. To check plants for spider mites, shake several suspect leaves or branches over a sheet of white paper. Look closely at the specks which have fallen on the paper. If they are moving, they are spider mites.

Bronzed or abnormally reddened leaves indicate cold temperature damage or a deficiency of phosphorus or potassium. Check the recommended temperature range for the plant. If a nutrient deficiency is suspected, fertilize with a complete fertilizer or repot in new soil.

Unnaturally small pale leaves and spindly plants are most generally the result of insufficient light. This is especially common during the winter or when outdoor or greenhouse grown plants are brought into the home. Small leaves might also indicate a need for fertilizer.

Figure 3. Soluable salt Injury on fern.

Brown leaf tips and margins can be caused by exposure to hot dry air, improper watering, insect feeding, salt accumulations (Figure 3) or objects rubbing against the leaves. Water which is chlorinated or contains added or natural amounts of fluoride can harm sensitive plants. Perlite (the white material in many potting mixes) and fertilizer products containing fluoride may release enough fluoride to harm sensitive plants. Spider plants, especially the variegated variety, are very sensitive to fluoride and are often seen with leaf-tip burn. Occasionally flushing the soil should help to reduce a fluoride salt buildup.

Bleached or faced spots on leaves are sometimes caused by direct sunlight burning plants that require shade or are not yet accustomed to large doses of direct sunlight. Chemicals and plant cleaning products can also injure leaves.

Figure 4. Oedema on geranium leaf.

Other leaf spots, varying in description, may be caused by aerosol products, hot grease in the kitchen area, cold water (especially on African violets and gloxinias) or the sun shining on wet leaves. In rare cases a pathogen may be involved.

Plant distortion (leaf thickening, curling, leaf and flower drop) accompanied by leaf yellowing and browning may be due to gas fumes or pesticides which are toxic to the plant. Plants are very sensitive to gases and will show symptoms before the gas concentration is at a level detectable to humans. Garden soil that is contaminated with agricultural chemicals and used for potting house plants can result in chemical injury to the house plants.

White substances on the soil surface may indicate two things. If crusty or crystalline, it's probably an accumulation of salts. The crusty surface layer of soil can be removed and replaced with fresh soil between repottings. Refer to the section on "Feeding" for more information.

A white or light yellow mold-like growth may indicate the presence of a saprophytic soil fungus, a fungus that lives on dead or decaying matter. The fungus will not harm the plant but may indicate unsterile potting medium or an overwatered plant.

Light brown corky scabs, usually occurring on the underside of leaves and along stems, are the result of excess water (Figure 4). This condition is known as oedema. Careful watering and good drainage will minimize this problem.