Season

• You have two options for spreading weed and feed on your lawn: spring or fall. You might opt for both, but that depends largely on the condition of your yard. Never apply it more than twice per year. Apply weed and feed in the early spring. Target the early part of the growing season, but make sure to apply it only when weeds are actively growing. If you apply it before weeds appear, it has a limited impact.
  
  Weed and feed prevents the germination of seeds. Therefore, you must avoid planting grass seed for at least four weeks after applying weed and feed. If you apply weed and feed in the spring, consider planting seed in the fall. If you apply weed and feed in the fall, plant your seeds in spring.
  
  

Other Factors

• Before you use weed and feed products, make sure the weather agrees with your plans. You must wait at least two days to water your lawn after you apply weed and feed. Therefore, your lawn should have plenty of moisture before you apply it. Avoid using it during dry spells. If rain is expected, your weed and feed is likely to be wasted because it runs off in water. You should apply it when the forecast calls for no rain for at least two days.
  
  You also should apply weed feed when your grass is at a normal height, but wait a few days after mowing before applying it. This ensures that it targets weeds that are actively growing.
  
  

Considerations

• While you want to do your weed and feed and seeding at a particular time, there are some instances in which you might not want to do so at all. According to the Public Health and Social Services site for Thurston County, Washington, the vast majority of weed and feed products contain herbicides. Many of these herbicides pose health risks to children, pets and animals. The health site says some studies indicate a link between herbicides and serious illnesses such as cancer and neurological diseases. These products, when applied to your lawn, can be tracked into your home.
  
  The public health site in Thurston County recommends an alternative. Using a mulching mower and leaving clippings on the lawn can provide one-third of the nitrogen the grass needs each year. This reduces the need for fertilizing. The site also recommends using a weed-killing spray to directly tackle weed problems instead of applying weed killer to the entire yard.