Feeding your indoor plants the right amount

During the course of centuries, your indoor plant evolved and adapted in a natural environment. The rain watered it, light and warmth were provided by the sun, and the earth itself held the chemicals used by the plant to make food. Even if the plant died, or was killed, its constituents returned to the soil to become food for its successor. When supplies close at hand ran low, rain would probably leach more chemicals through the soil to the plant. Failing this, the roots would spread and forage further afield.

Compareplant-food-tablets with this the artificial environment in which we expect indoor plants to flourish. There is no rain to wash the leaves, or to dissolve the soil chemicals; instead we spray and water. As the roots are confined inside pots, they cannot spread to seek more nourishment. When the plants have consumed the nutrients in the compost we give them, we have to provide fresh supplies of synthetic food which match their synthetic climate and environment. Incredibly, in these conditions, with the simple addition of what we call Plant-Think they thrive, growing strong and beautiful.

To produce healthy growth, fine flowers and good foliage, plants must have supplies of nitrogen, phosphorus, potassium (potash) and numerous trace elements. They are best provided in a compound fertilizer that contains them all. Complete fertilizers may be easily obtained either in solid or in liquid form, chemical or organic. The liquid is by far the best for indoor plants. ‘Baby Bio’ is just one example of the good proprietary brands. It is a highly concentrated plant food which contains extracts of humus and seaweed, vital organic elements necessary to plant health. Simply diluted with water, it gives an even distribution of nutrients to the plant roots throughout the pot, avoiding the danger of starving the roots in one section of the pot while giving those in another a concentration so strong that it is toxic.

Always remember to feed plants sparingly; tiny, balanced doses are what is required. If a plant needs more nourishment, it will show symptoms which you can easily and quickly rectify. The effects of overfeeding are much more harmful. Some plants will use more of one chemical than another. In that case, a build-up of surplus nutrients in the compost may result in a concentration that is harmful to the plant. Moderation in the supply of feed should avoid this calamity, but if it occurs, feeding must be stopped. Watering with rainwater, which can dissolve more chemicals than tap water, may help to remove the surplus. Nevertheless, the plant will have suffered a serious check. It may take a considerable time to recover and will, perhaps, lose its verve for life, always remaining rather a sickly specimen. To repeat the message then: if in doubt, don’t!

Two vital rules that must be observed when feeding indoor plants:

  1. Never feed a ‘dry’ plant – get the soil into the right condition first.
  2. Never, never, never give an extra ‘slurp’ of food as though it were a treat – it could easily prove fatal!

Foliar feeds, specially formulated nutrients for spraying on the leaves, can be another aid in keeping your plants healthy. Like the systemic insecticides and fungicides, they are absorbed by the plant. They promote healthy, good-looking leaves and thus supplement normal feeding, but they do not provide an alternative to it. They act very rapidly.

You will find it very helpful to understand the prime function of the main constituents of a good plant food: so do read this.


In a natural environment, nitrogen is obtained from nitrates in the humus contained in rich soil. It is necessary for growth and the production of good foliage with rich green colour; an excess will result in lush, soft growth and fewer flowers.


Obtained from phosphates in the soil, phosphorus is essential for the formation of strong, healthy root systems resulting in vigorous plants which produce good flowers and seeds. Plants lacking the chemical will be stunted, with poorly developed root systems which, in extreme cases, cannot adequately support the plant.


Potash has been called ‘chemical sunshine’ because of its effect. It assists the production of good flowers and fruit. An inadequate supply results in small flowers of poor colour; stems are brittle, and the plants are prone through weakness to attack from disease.

For answers to the questions of when to feed, and how much, we are back to Plant-Think. It is obvious that a tiny, slow-growing cactus will need far less food than a large and vigorous Rubber Plant. During the entire spring and summer, the cactus will be happy with about three feeds while the Rubber Plant will need feeding at almost every watering.

The system to adopt is to water those plants not in need of feeding. When they have been dealt with, refill the watering can, add the liquid plant food and water the remainder. They are then fed and watered simultaneously. The quantities given should be those advised by the makers of the food used.

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