It should state on the Preen Instructions and Cautions. My mom and neighbors uses it an the weeds eventually come back same season so it's not long lasting. She's taken to often using white vinegar and Preen afterwards as cheaper and more effective than Round-Up and something that will last a couple of months.

Sorry to hear about that. Can you stretch to the end of summer before seeding? Seeding in summer is the very worst time of year for new grass. The grass doesn't become sturdy enough before the heat gets it.

But if you had mulched the area, why did you Preen it? Wasn't everything dead under the mulch?

We removed some bark mulch under some large windows in a solarium because artillery fungus developed in the mulch. It is impossible to get rid of this fungus and when the spores shoot more spores onto the windows and siding it is very difficult to remove. We are going to put decorative stones here instead. The Preen was to keep weeds from growing during the transition. A large patch of grass is crispy brown after the Preen runoff.

I was actually going to use mulch but have changed my mind because of all the loose cats that wander the neighborhood use the mulch as a little box.

I will plant up tightly in English lavender and fairy roses were I want to mulch instead.