It is always disappointing when a cherished specimen suddenly looks sickly, and it is so often the more expensive types which succumb first. There is not going to be much pleasure in growing indoor plants unless you learn how to avoid plant troubles.
Specific pests and diseases are not usually to blame; in most cases the cause of illness or death is either too much or too little of one or more of the essential growth factors.
There are scores of possible reasons which can account for the death of an indoor plant. The seven most common fatal factors are:
1. Soil dryness. No life can survive without water. Many plants can cope with infrequent watering in winter but failure to provide sufficient water during the growing season soon leads to wilting of the leaves and finally to the death of the plant.
2. Overwatering. The most usual cause of plant death in winter is overwatering. The leaves of affected plants droop, and the owner thinks that they are short of water. So the plants are thoroughly watered and collapse soon follows.
It is obviously vital not to confuse the symptoms od drought with those of overwatering. Both cause leaves to wilt and sometimes to drop, but too much water results in yellowing of the foliage, whereas dryness is much more likely to cause shrivelling and browning of the leaves. Also waterlogged clay pots are covered with green slime.
3. Cold nights. The harmful effects of cold nights are heightened if the plants are kept under warm or hot conditions during the day, as it is the sudden fluctuation in temperature rather than cold air which usually causes the damage.
Frost is generally fatal, and plants standing on windowsills are the ones most likely to suffer. Never leave pots between the windows and drawn curtains on a cold night; if frost is expected and the room is unheated then move the plants away from the window.
4. Hot dry air. With central heating, and with most forms of artificial heat, the air lacks moisture and conditions are not favorable for most indoor plants. Delicate plants may die under such winter condition, and it is necessary to increase the relative humidity of the surrounding air.
5. Draughts. When a door and window are opened in a room, and when the temperature outside the room is lower than within, then a cross-current of air occurs and these draughts are an important cause of plant failure. For this reason, avoid standing plants in a direct line between door and windows.
Another spot which is subject to draughts is the windowsills where there are cracks in the window frame. If delicate plants are to be grown on a windowsill, it is essential to block up all cracks.
6. Strong sunshine. Some plants will quickly succumb if exposed to direct sunlight even if the air temperature is not unusually high. Some flowering plants, such as Pelargonium, thrive in a sunny window but even these, in common with all other plants, should have the pot and soil surface shaded in the hot summer months. If this is not done, the soil may be baked and the roots killed.
7. No light. Poor light conditions in an average room do not usually kill; the result is generally pale, weak growth and no flowers. There is a level, however, at which the amount of light is not sufficient to support house plant life and this can occur in dark passages, corners of large rooms, hallways etc. If you wish to keep plants in such areas, return them at regular intervals to a moderately well-lit spot for a fortnight’s holiday.