The leaves of a house plant can turn brown for many reasons; some of those reasons are environmental, while others deal with water quality and proper fertilisation. To reduce the possibility of the leaves on your house plants turning brown, always know the growth requirements of each plant, including humidity levels, temperature, light, fertiliser and whether the plant likes to be root-bound.
Browning of Edges
The browning of a plant's leaf edges can be caused by temperatures that are too high or humidity that is too low. If the room temperature is too high, move the plant to a new location. If the humidity is too low, place the plant on a tray with pebbles and fill the tray with water. Monitor the water level in the tray so that there is always water available for evaporation and humidity.
Browning of Tips
A plant whose leaf tips are turning brown can be suffering from many different conditions, most of which have solutions. In addition to low humidity, brown leaf tips can be caused by fertiliser burn; this condition can be fixed by repotting the plant in fresh soil. Many of the water additives used to improve water quality for humans, including salts, fluoride and chlorine, are harmful to plants. To fix this problem, always let the water set 24 hours before using it to water plants. Incorrect fertiliser application, which can cause the tips of plants to turn brown, can be prevented by following the manufacturer's instructions when applying the fertiliser. To prevent or resolve leaf browning because of incorrect soil pH, test the soil and adjust accordingly and/or repot the plant. A too-high pH can cause iron deficiency, while a too-low pH cause magnesium deficiency. To prevent leaf browning due to indoor air pollution, keep all plant material away from areas where chemicals and gas are used.
Insects feeding on house plants can cause the leaves to turn brown. Check the stem and underside of each plant leaf for insect infestation. Remove insects such as mealy bugs, aphids and scale with tweezers; spider mites will need to be washed off every three to four days. If you find insects, avoid applying a pesticide to the plant material indoors. If the insect infestation is severe, apply a pesticide to the plant outdoors, or discard the plant.
Plants that are root-bound can exhibit browning leaves. To prevent this, always check to see if the plant's roots are going through the drainage hole in the bottom of the pot or are coming up through the top. If either one of these is the case, repot the plant into a container that is 1 to 2 inches larger and add fresh soil as needed.