Looking After Plants

Indoor plants are subject to attack from a wide variety of pests and diseases. The damage caused is very variable and the symptoms are not always obvious. Insects and mites usually cause physical damage to the plants by feeding on them. Sap sucking insects plumb into the vascular system of plants and extract sugars and proteins whilst, at the same time transmitting viruses. Damage is caused by the removal of vital fluids from the plant and the destruction of tissue.

Mites and thrips cause damage by puncturing cells on the surfaces of leaves and sucking out their contents, thus killing the cells and leaving a permanent scar on the leaf. Caterpillars and weevils feed by biting and chewing plant tissues. Vine weevil larvae, for instance, feed exclusively on roots and the damage they cause is not noticeable until the plant suddenly wilts. Unfortunately, by then it is too late.

Bacteria and fungi also attack plants. They often invade the plant through wounds or by the pores in the leaves (stomata). They damage the infected plants by feeding from its tissues and releasing enzymes and other growth substances into the plant, often causing distortions and unusual growth patterns.

Indoor plants are usually grown in lightweight growing medium such as peat. They are in containers, so all the nutrients that they need have to be provided. If too much or too little nutrition is provided, then a plant may exhibit symptoms. Unfortunately, symptoms of excess and deficiency are often similar, so detailed chemical soil analysis may be required to determine the precise cause of the problem.

Not only does the concentration of nutrients in the soil have an effect, but so does the proportion of the nutrients and the soil pH. An excess of one nutrient may prevent the plant from extracting another, so symptoms of deficiency may be seen. The pH (acidity) of the soil also affects the uptake of nutrients, regardless of the quantities present and may have different effects on the uptake of individual nutrients.

Indoor plants are often kept in an environment devoid of natural wind and rain. Pollutants in the atmosphere cannot be blown or washed away, so their effects may be more severe than when outdoors. Additionally, indoor plants are exposed to pollutants that no wild plant would experience, such as volatile organic compounds or ozone from electrical equipment.

Light, temperature and humidity all affect the health of plants. Sudden changes in any of them may result in plants showing signs of stress. This is especially important in offices that close for long periods during holidays when lights and heating may be switched off.

We want to make sure everyone is able to look after office plants. If your plant is beginning to show signs of distress, the following pages may help you to identify what is causing the problem and provide advice on how to care for your plants to help prevent future disorders.