Before you buy fertilizer for your garden, be sure that you understand what's available. The following list offers the common types of garden fertilizers and explains their components and uses:

  • Complete fertilizers: These contain all three macronutrients — nitrogen (N), phosphorous (P), and potassium (K).

  • Incomplete fertilizers: These are missing one or more of the macronutrients, usually the P or the K.

  • Chelated micronutrients: These are in a form that allows a plant to absorb them quicker than the morecommonly available sulfated forms. If your plants just won't green up (they stay mottled yellow and green, or just plain yellow), no matter how much nitrogen you apply, you probably have a micronutrient deficiency of iron, zinc, or manganese.

  • Foliar fertilizers: You apply these to a plant's leaves rather than to its roots. You can use most liquid fertilizers as foliar fertilizers, but make sure that the label instructs you accordingly.

  • Organic fertilizers: These fertilizers derived their nutrients from something that was once alive. Examples include blood meal, fish emulsion, and manure.

  • Slow-release fertilizers: These provide nutrients to plants at specific rates under particular conditions. Some slow-release fertilizers can deliver the benefits of their nutrients for as long as eight months.