Just as we water houseplants because rain doesn’t reach them, so we need to feed them because their roots aren’t able to reach out for nutrients and nourishment.
For best results feed regularly when the plant is actively growing or flowering. Allow plants a resting time when watering is reduced and feeding halted; this is usually from autumn to late winter, except for winter flowering houseplants.
The major plant nutrients
Potassium (K): Helps to improve flower quality. Strengthens a plant’s resistance to disease.
Nitrogen (N): For strong, healthy stems, leaves and shoots. Provides good colour to leaves.
Phosphorus (P): For sturdy root growth.
The minor nutrients
Other nutrients essential for plant growth include magnesium (Mg) - which is used in formulation of chlorophyll in leaves, sulphur (S) and calcium (Ca).
Feeding when you water
Use a quality pot plant food such as ready to use plant food, which supplies a balanced range of plant nutrients. Most plants should be fed every 10 days or so from April to September. With winter flowering plants this feeding period will be during their bud formation and display time. Add a capful of houseplant food to one litre of water and water the plant in the usual manner. ready to use plant food is a ready diluted plant food that can be poured directly onto the compost of established pot plants. Pour a capful of the nutrient rich food onto the compost every couple of weeks and water in the usual way with plain water.
Feeding acid lovers
There are many pot-grown plants that appreciate acid (lime free) compost conditions and need extra iron for healthy growth. These include azalea, rhododendron, gardenia, citrus and camellia. Feed these plants during the growing season with soluble plant food. It helps stop leaf yellowing. Mix 3 small bowls of soluble plant food to 2 litres of water. Water plants every 2 to 4 weeks when actively growing. Stop feeding when plants are dormant.