Does Weed and Feed Fertilizer on Newly Seeded Grass Kill or Harm Grass?

Herbicide Use on New Grass

• The management of newly seeded grass required special attention, since the seeds and new seedlings are highly sensitive to chemicals. The choice of herbicide for new lawns should be made only when weeds are getting out of control and there is no other option, according to the University of California Extension.

Weed and Feed Use Recommendation

• Weed and feed products contain either postemergence or preemergence herbicides. Since you are unaware of what kinds of weeds you are likely to encounter in your lawn, herbicide will damage only the new grass seed and seedlings. Weed and feed products are designed to work on established grasses.

Fertilizing New Grass

• Newly seeded grass does not require immediate fertilizing. Start to fertilize the new lawn after six weeks of seeding, as recommended in "Toro Expert Guide to Lawns." When you start to fertilize, use a very light fertilizer, such as ½ pound of nitrogen for 1,000 square feet.