Fertilizing is beneficial during the period of active growth from spring through summer to early autumn. In late autumn and winter, discontinue fertilizing altogether except for those plants which make growth during these periods.There are many good brands of house-plant fertilizer available from florists or garden supply stores. Always follow the manufacturer's instructions, because exceeding the stated dosage will only harm the plants. The small bottles of fertilizer which come in liquid or powder form are perhaps the most convenient to use in the home.

A trap which many inexperienced house-plant enthusiasts fall into is that of attributing the unhealthy appearance of a plant to starvation. Try to determine first whether the unhealthy symptoms are caused by damage from cold, over-watering, or excessive dryness. If these possibilities can be excluded, take the soil out of the pot to make sure that the roots are healthy and undamaged. This can be done by spreading the fingers of one hand on either side of the stem between the lower leaves and the top of the pot. Invert the pot, and tap the rim sharply two or three times. The soil ball will then fall out into the hand. If all is well with the roots, fertilize the plant. Pale-green leaves usually indicate the need for fertilizing, particularly if the plant is pot-bound (that is, the pot is full of roots).