Poa Annua germinates primarily in the fall each year so you would want to use a pre emergent herbicide in the fall to help keep it from coming up the following year.
Hi-Yield Weed and Grass Stopper with Dimension contains dimension pre-emergent which provides superior control of crabgrass as well as control or suppression of other listed weeds when applied before they germinate. This product will also provide post-emergent control of crabgrass only and is effective on crabgrass up to 4 to weeks after it has germinated and emerged.
Hi-Yield Crabgrass Weed Control is a pre-emergent only and must be applied before crabgrass weeds germinate and emerge from the soil.
Per the product label on Hi-Yield Weed and Grass Stopper with DImension Herbicide, for best results, apply this product within a few days of mowing or delay mowing again for a few days after application.
The herbicide in Hi-Yield Weed and Grass Stopper with Dimension Herbicide is only a pre-emergent product that prevents weeds from germinating. It will not kill any actively growing weeds. If you are dealing with grassy weeds, Bonide Grass Beater Over the Top would be great to use. Otherwise Lontrel is great for broadleaf.
Hi-Yield Weed and Grass Stopper with Dimension Herbicide should be applied in mid February to early March when soil temperatures are above 55 degrees Fahrenheit.
Also, please check out our Warm Season Lawn Guide. There are excellent tips on how and when to use the various products for your lawn.
Hi-Yield Weed and Grass Stopper with Dimension Herbicide can be applied to St. Augustine lawns. It is not specifically labeled for Floratam species. With this being a sensitive turfgrass, we suggest discussing product applications with the Master Gardener at your local cooperative extension office.
When using Hi-Yield Weed and Grass Stopper with Dimension Herbicide in Northern areas like IL, you have different application rate options, depending on how long you need the residual to last, and whether you plan