Potted plants rely on you for food because their roots can’t go searching through the ground. A common schedule is to fertilise lightly once a month during the active growing season (spring and summer) and reduce or stop in winter when many plants slow down.
Use a balanced, gentle fertiliser and follow the instructions – more is not better. Overfeeding can burn roots and cause yellowing or droopy leaves. It’s safer to give a smaller dose more regularly than a huge dose once in a while.
Signs that plants might want feeding include pale new growth, very slow growth despite good light, or leaves that look “thin.” Just make sure other basics – watering, light, pot size – are correct first. Fertiliser won’t fix plants that are drowning, burnt by the sun or trapped in tiny pots.
Think of fertiliser as vitamins, not magic medicine. A little, at the right time, keeps container plants healthy and productive, especially flowering plants and heavy feeders like tomatoes and herbs.