Question
I live in SE Wisconsin and have new sod that has been watered over the first 2-3 weeks to get it started and then watered occasionally the last 4 weeks. I have cut the grass 3 times and have crabgrass in several areas and also some lighter broad leaf grassy weeds coming up between the seams of the sod. The grassy weeds grow three times as fast as the grass and look horrible especially in the corners and sides of my house that did not get as much water as others. Also, I just fertilzed my lawn with Scot's Lawn Food to insure that the sod stays strong. Here are my questions:

1) When can I use a weed and feed type of fertilizer?
2) Would the standard Scott's weed and feed products help on these grassy weeds?
3) Should I use crabgrass killer as well and just spot treat these areas?
4) Can I use them at the same time?
5) Should I be mulching my lawn clippings with new sod and these weeds or should I be bagging them to prevent the weeds from spreading?
6) Finally, how often and when should I start aerating my lawn? Does the frequency of mulching/bagging clippings come into play when making this decision?

Answer
You can use weed-and-feed fertilizer in fall (september or october). Apply when the lawn is not draught stressed and apply to WET turf. Let the product stay on the grass (and weeds) for the time listed on the lable, then water in well.

weed-and-feed will work against broadleaf weeds (clover, dandelion) not grassy weeds.

I recommend that you pull/dig crabgrass right now and then apply a pre-emergent herbicide (fertilizer w/crabgrass preventer) in early spring (april) so combat crabgrass. Do not apply too late. If in doubt, ask a local garden center when it is right to apply crabgrass preventer (must be in spring before soil temperatures get too high).

You can use Round-Up to kill the grassy weed. If it is taller than the regular grass, then use a paint brush and carefully dip the brush in the herbicide (no spilling allowed) and then brush the leaves of the grassy weed. The taller weed will then die. If possible, cover the grass below with cardboard (trap tall grassy weed between the two pieces of stiff cardboard) so any drips fall on the cardboard.

Finally, you can dig the taller pieces of weed and put some new grass seeds on this "empty" spot.


Do not apply more than one type of fertilizer at one time. In fact, only fertilize in spring and fall. If you fertilize with crabgrass preventer in early spring (april) then postpone the second application to mid may. Then repeat in september and again in october. Do not fertilize in summer.

Always apply to a dry lawn (e.g. not a wet lanw, but do not fertilize a draught stressed lawn). water in well. Only exception is the weed-and-feed which must be applied to a wet lawn (see above).

if you use commen commercial fertilizers such as 29-3-4, 33-3-3, etc then apply no more than 3 lbs of such fertilizer per 1000 sq feet per application. if your lawn is (say) 50 x 100 (5000 sq feet) you would meassure out 5 x 3 = 15 lbs and then put it in the spreader. Set the spreader at a LOW setting and apply evenly by running over the lawn in various directions (north/south, east/west) untill all product is used up. It is better to apply at low setting and running over the lawn more times than applying too much.

Do mulch mow and recycle clippings. this is highly beneficial to the lawn. A few green leaves from grassy weeds will not hurt this (only help).

If you just planted the lawn, then aerate in another year or two and then repeat every 2 years. This is not a top priority.

I recommend that you mulch mow every time you mow, maybe with exception of first mowing after weed killing applications (bag and discard, do not compost). But otherwise, mulch mow. I like to mow frequently (twice weekly in spring and fall and weekly in summer).