The roots of garden plants will spread through the soil in search of nutrients, but planter-grown houseplants rely on you for the minerals they need. As a rule, plants in containers should be fed regularly during their growing season, which is usually spring through fall. You can use any generic plant food according to the manufacturer's directions, but always use caution not to over-feed, as this can cause root burn and accumulate too many nutrients in your soil. We prefer time-release fertilizers so that your plants receive small amounts of nutrients at every watering.