Crabgrass pre-emergent also prevents grass seed from germinating. It sounds like you need a renovation and the time to do that is late August/early September. I suggest you let whatever grows grow this spring. In July use glysophate to kill everything. Water to encourage weed seeds to germinate and in a few weeks use glysophate again to kill everything. Sow grass seed in late August and water appropriately. This spring you should get a soil test and add amendments needed to get your soil in good condition for a fall planting.

After killing everything the second time and before sowing seed, you should mow the dead grass and weeds on the mower's lowest setting, bagging the clippings. In spring of 2016 use a pre-emergent when the forsythia bloom.

Thanks for the advice! So, you're definitely saying the pre-emergent crabgrass preventers that are included in many starter fertilizers (Tuperan/Tenacity, etc) are worthless and that I'd have no luck with a spring planting if I used such chemicals?

Thanks!

Tenacity can be used at seeding time and it's effective. It can be reapplied 21-42 days later. But it can't continue to be reapplied. You have to be precise in your measurements and spraying and use a surfactant. Tupersan can also be used and it's effective. It can be reapplied at 4 weeks. Not sure if it can continue to be reapplied. With either one, you will have the problem that your grass won't develop enough roots before the summer heat hits. If it's not the crabgrass, it's the heat.

Even without a pre-emergent, summer survival of spring planted grasses is touch and go (the pre-em actually doesn't cost you much, if anything at all). They simply don't have time to develop adequate root mass before summer hits.

Consistent watering can get you around that...and of course, can also set off some nasty fungal issues. But those can be dealt with as they arise.

Tupersan or Tenacity are fine at seeding time, and can be reapplied. Once. That will get you through the silly season of weed growth and into the earliest part of summer.

Post that, the optimal answer is to wait until the grass has been mowed three or four times, then spot-spray weeds that do sprout and use a pre-emergent again at that point. Crabgrass will continue to sprout until soil temperatures drop under 65 or so (it's most energetic warmer), so even a late-applied pre-emergent has some benefits.

You're likely to still have breakout issues for some years. Pre-emergents are around 90-99% effective. Crabgrass can drop hundreds of seeds per plant without half trying. So some will still sprout.

Fortunately, Weed B Gone with Crabgrass Control is very effective on sprouted crabgrass, and can be spot-sprayed even when the lawn is very young. It may damage or kill some surrounding grass at that point, however. By the third or fourth mow, the grasses will be much more resistant to it and damage will be minimal, if any at all.

Very late summer is certainly the best time to seed. The grass has all of fall and early winter to grow roots, it doesn't mind winter in the slightest, and spring is another root growth season. So it essentially has two full seasons and some part of another before summer hits...which grasses hate.

However, life and bare ground get in the way of that. Late winter/very early spring seedings do tolerably well if cared for the first summer. Just remember to water.

If it were me? I'd seed now to take advantage of the last tick on the clock of dormant seeding, accept the fact that survival might not be great, control weeds by spot-spraying until I could get a pre-em down (and then continue to spot spray as it won't be perfect). Then overseed again just as temperatures start to fall off at night at the end of summer if I needed to.

By next spring, you'll be able to drop a pre-emergent shield and keep it up all season long. The grass will be old enough.

If you're planning to use a regular pre-emergent later on in the spring or summer and you also want to overseed this fall, be sure to check how soon you can plant seed afterwards. It will be included in the directions for whatever pre-emergent you're using. I use Dimension and the soonest you can reseed with that is 3 months if using only one application and 4 months if using split applications.