Let there be light
In a sense, light to a plant equals food! Human beings live on chemical substances, but are unable to survive on them until they have been rendered into absorbable form. The steak you eat, for example, is broken down by the process of digestion.
In the case of plants, chemicals pass into the and are conveyed to the through the sap of the plant. But mostly, the plant makes its own food by the process known as photosynthesis; it uses the energy in light – usually sunlight – to make carbohydrates like glucose, sugar and starch from water absorbed through the roots and carbon dioxide from the air. They are enabled to do so by the green chlorophyll in their , which works as a catalyst. Without light no food is built up. If the leaves turn yellow, it means that no food is being manufactured to keep the plant alive.
A photographer’s light meter taken outside on a bright day will indicate high intensity; carry it at once into a bright room and the needle will barely register any light at all. Your plant, which once lived in the open, is similarly affected. The lower light level means that less food is made, and the giant of the rain forest grows as a dainty but healthy dwarf.
It is of course true that in nature many plants live in shaded conditions, but even so the total light from all sides considerably exceeds that available from the limited window area of a room. The plants are indoor plants because of their ability to adapt to these low light levels. It is wise to give them all the light that you can make available.
Few indoor plants require, or will even tolerate, more than 22 C (70 F) of warmth, yet in their tropical homes they are happy with much higher temperatures. This is because there is a balance between the light and the warmth.
In nature, warmth and light come from the sun. At the time when it is at its brightest it also gives most heat. If, by some means, its light is reduced (say, by the shade of trees) the temperature then goes down.
Your indoor plant is receiving comparatively little light and therefore needs less warmth to maintain a suitable balance. It has already been shown that less food is made in the leaves when the level of light is reduced. At the same time they will be giving off less moisture. Too high a temperature in relation to the light will result in excessive evaporation and the leaves will dry out.
What plants do object to are sudden sharp fluctuations in temperature. Imagine the effect of a cool bright winter’s day with good light and a little heat. At nightfall, even with artificial illumination, the light is reduced to a fraction of its daytime level. The heating is increased, however, to keep the humans warm, and the temperature rises considerably. Each in itself is bad enough, but the change in the light-warmth balance is of gigantic proportions.
Air – let it circulate
Humans need fresh air; their lungs extract oxygen from it and they exhale the carbon dioxide. Unless the air is changed regularly, the oxygen in it is exhausted.
Plants have roughly similar needs and the air around them should circulate freely to help remove traces of gas or other toxic fumes. Good ventilation also has a mild prophylactic effect. Plants given a regular supply of fresh air, provided it is not accompanied by a sharp drop in temperature, are less likely to be attacked byor fungus diseases.
Ventilation and fresh air emphatically do not mean draughts, which cause sharp drops in temperature and– very harmful to all indoor plants, even the most sturdy.
Dust is a plant enemy which makes the foliage look dull, blockspores and inhibits the plant’s respiration. In towns, it often contains damaging or corrosive chemicals. A covering of dust also reduces the life-giving light which the leaf needs.
Dust can be removed by spraying and gently sponging the leaves with clean water. Ignore very young leaves until they grow larger so as to avoid damaging them. If the foliage is extremely dusty, it should be gently brushed with a feather duster before washing; otherwise the plant pores will be clogged with a sticky mud containing the unwanted chemicals and, after drying out, the plant will be worse off than it was before it was treated.
It is possible to polish large strong leaves with specially developed cleaners such as `Bio Leaf Shine’. Apply by gently wiping the leaves with a pad of cotton wool soaked in the liquid. The shine is usually long lasting and does help to keep the leaves dust-free.