The label on these products usually tell how long after seeding. If not, it should be mowed a couple of times before laying it down. With that said, you may miss the opportunity to use a pre-emergent depending on where you are and what the temperatures are doing. Spring weeds will start to germinate when soil temps hit high 50's, low 60's. Once they germinate, pre-emergents don't do much good.

I have a large area of turf in a rural area that alwys will get some weed infestation. Usually I spot treated with 2,4 or a similar product. But this Spring did tried a new product6 and it was fantastic! It is SpeedZone. It works very well in cold weather. I used just less than 1 oz. per gallon in a hose-end sprayer over the entire turf area. It is rain-fast in 3 hours. After 1 week the chickweed, henbit, etc., that was starting to take over was completely destroyed. I then fertilized in mid-March and with the warm April weather the density of the new turf and lack of competition has filled in completely. After the first application, there was some yellowing of the ends of the blades of the fine fescue in the lawn. But after 1 mowing it was back to normal. Also I advise not use use a surfactant or adjuvant with this product which may reduce it selectivity on broadleaf weeds only. Also, I would not get it near shrubs as the product can be absorbed from the roots and damage the plant. In mid-April I inspected the lawn again and spot treated with the same product for late germinating weeds. I used less than half of the amount of liquid I would normally use to spot treat at this time of year. With spot treatment I noticed no yellowing of the grass blades.

well, part of the reason for the "oversized" lawn is because its what was here when i purchased the house, i probably wouldn't have gone through the effort of clearing that large an area. Approximately one acre of the lawn is really an orchard that i keep mowed because i like the look of it mowed as opposed to not mowed and find it easier to work in when not tromping through 3 feet of weeds and grass. The rest of the yard I have various gardens, vegetable and flower mixed across it. I can understand what you are saying about the medow but the distance to the woods on any one side isn't that large and to have a narrow section of field grass between an imaginary lawn line and the woods i think would look unkept. Also i figure if i can control the weeds all around up to the woods line then there will be less of a battle yearly as there will be less seeds to fight year after year. I do keep the grass cut at 3 inches in the spring and fall, 3.5-4 in the summer. Possibly dandilions grow smaller in other areas as i have often read the 3 inches to get rid or control dandilions, but I have never had any luck with that theory anywhere i have lived. thanks for the info rdaystrom, I'll have to take a look to figure out what the predominant grass is in the lawn at the moment.

Most of the weed killers will have instructions on the package regarding the best time to put them down. Most will require that the weed is actively growing for best results. Applying weed killer at over 85 deg risks doing damage to the grass. You probably are best spot weeding the broadleaf weeds. I have not done it, but applying multiple types of weed killers at the same time will likely over stress your grass. Out here crabgrass and Nutsedge starts to disappear in September. You might want to wait and let nature take its course. However, I am a right coaster; you should wait for a response from a more knowledgeable left coaster. Capt Tom