If you do need to feed a tree, shrub, lawn or flower bed, the best place to put the fertilizer is on the surface of the soil or mulch. Plants that need frequent feedings include fruit trees, flower beds, herbs and vegetable gardens. All plants kept in containers also need a constant source of nutrients. Fertilizer can be applied through granular or liquid products. It's always best to follow label instructions.
Some gardeners also like to use manures as their major sources of plant nutrients.
Many fertilizers can time the release of nutrients. Such slow-release products help plants make maximum use of the nutrients and prevent leaching of extra plant food through the soil and into water supplies. Fertilizers can make a sick plant look better or encourage flowers if the nutrients needed for growth are missing from the soil. They won't solve water problems or cure plants that have insects or those affected by most diseases. By supplying extra feedings to yellow or slow-growing plants, you can improve the color and encourage new shoots.