Essex,
United Kingdom 
how soon after using weed and feed on a lawn can you re seed?
18 Sep, 2010
Answers
Around here, some Weed & Feeds have a pre-emergent, and will prevent new seedlings from sprouting for up to 6 months. Look for the phrase "Prevents Weeds!" on the bag.
18 Sep, 2010
Previous question
six weeks after the application of weed and feed, assuming you used a granular treatment.
18 Sep, 2010