Reseed or Treat for Weeds

The following questions were sent to the P&PDL diagnosticians here at Purdue University:

Question 1: My lawn is abut 50% grass, 25% weeds, and 25% bare spots. I would like a fuller weed free lawn, but I don't know if should reseed, fertilize, kill the weeds or all of the above. What should I do, and can you recommend some good brands to work with.

Answer 1: Information on this and many other lawn topics can be found at the following web page: http://www.agry.purdue.edu/turf/ If you still need help, you can contact the turf specialists in your state found under "Turf Links" and "Other Universities" on that web page or you can contact the Indiana turf specialists through that page. Good Luck!

Question 2: We have a lawn (on a sand hill) that is doing fairly well, but has a lot of weeds. Should we reseed the bare spots now (fall) OR spray the herbicides now and get rid of the weeds?

Answer 2: What kind of weeds are in the lawn?

If they are annual grasses, I'd just mow short, aggressively rake to stir up the soil and reseed. Then I would apply 0.75-1.0 lb/1000 sq ft. N in mid-September, mid-October and early November to help the seedlings fill but also to increase density of the established turf.

If they are broadleaf weeds, I'd do the same thing and also apply a broadleaf herbicide in mid-October, since you can apply most broadleaf herbicides to seedlings after they've been mowed four or more times.

If the weeds are perennial grasses like quackgrass or tall fescue, I would spray Roundup as soon as possible, let it work for 4-5 days, seed, and then follow the before-mentioned fertilization plan. Be sure to keep the reseeded areas watered to stimulate germination and establishment.

-Zac Reicher