Since the roots of houseplants are trapped and unable to go elsewhere, unlike in-ground plants that can look ‘elsewhere’ for food, they’re counting on you for feeding!
Houseplants need fertilizing with an all-purpose plant food, such as Schultz® Liquid Plant Food, Schultz® All Purpose Slow Release Granular Plant Food, or Bonide® 10-10-10 Liquid Plant Food. How much your plant will need will depend on how large the plant is, the size of its root ball, and what kind of houseplant it is.
You’ll want to fertilize during the growing season (Spring, Summer, and Early Fall). That way, the plant can use it’s energy to absorb the fertilizer properly and grow.
Research your specific plant and make sure to follow the instructions on the fertilizer package!