Once we have chosen the plant, given it the soil and light, fertilizers are important to keep them alive.
Fertilizing once in a week is a good plan to adopt except for winter. During winter, fertilizing once a month is enough. These fertilizers are widely available in liquid or solid form.
Potted plants require fertilizer more often than the one in the ground as the nutrients in the soil get used up by plants. Once the soil nutrients are used up, we need to add fertilizer for health and growth of the plants.
There are three major nutrients required by the plants. For potted plants, equal amounts of nitrogen, phosphorus, and potassium (10-10-10) works best.
Nitrogen: For growth
Phosphorus: For root health and flowering
Potassium: To fights off diseases and growth
In addition, plants also require minute amounts of micronutrients such as copper, iron zinc, calcium, sulfur, magnesium. Almost all fertilizers contain these micronutrients.
If a plant is changing color to yellow-green, dropping lower leaves and is getting weak; it can be a sign to add some fertilizer or to provide more sunlight or both.
Fertilize less often if growth is small and there are brown spots on leaves and spacing between leaves are more than usual.
Synthetic fertilizer may deposit soluble salt with time in the soil which may harm plants. Hence the natural organic fertilizer is preferable over a synthetic one. If using synthetic fertilizers, wash out the excess salt deposit once in while by adding enough water until water flows out.